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Presents research papers on immunology to be published by the periodical 'Immunology' in 2003. 'A CR1 polymorphism associated with constitutive erythrocyte CR1 levels affects binding yp C4b but not C3b,' by Daniel Birmingham et al; 'DS-Nh as an experimental model of atopic dermatitis induced by Staphylococcus aureus producing staphylococcal enterotoxin C,' by Tekshi Yoshioka et al.

The cell-surface glycoproteins CD44 and CD58 are involved in cell adhesion reactions. In this paper 12 monoclonal antibodies in CD44 and two in CD58 are described. Competitive binding assays using CD44 antibodies identified three distinct epitope groups. Antibodies in Group 1 and, with one exception (BRIC 214), antibodies in group 2, but not antibodies in Group 3, recognized epitopes that are sensitive to reduction and to trypsin or chymotrypsin treatment of intact erythrocytes, and so these epitopes probably reside on the N-terminal disulphide-bonded domain of CD44. Antibodies in CD44 did not inhibit the binding of CD58 antibodies to erythrocytes or vice versa. Quantitative binding studies using radioiodinated IgG measured 1888-5592 copies of CD44 and 1772-3290 copies of CD58 on normal erythrocytes. Similar measurements with radioiodinated Fab fragments gave values of 6508-10,450 (CD44) and 3457-7622 (CD58). Immunocytochemical studies indicated that CD44 is much more widely expressed in non-haemopoietic tissues than CD58. Comparison with previously described CD44 antibodies suggests that antibodies in our Group 1 encompass Hermes 2 and that those in Group 2 encompass Hermes 1. All the CD44 antibodies gave weakened reactions with Lu(a-b-) erythrocytes of the In(Lu) type by one or more methods. BRIC 214 and antibodies in epitope Group 3 were used to demonstrate that CD44 on these variant cells gives membrane-bound trypsin and chymotrypsin cleavage fragments of similar molecular weight to those obtained with normal erythrocytes.

This paper describes attempts to isolate and characterize glycosaminoglycan (GAG)-binding molecules on the surface of lymphocytes and lymphoma cell lines and relate their expression to splenic and lymph node homing capacity. Initial binding studies with radiolabelled GAG and rosetting studies with GAG-coupled erythrocytes revealed that there are receptors on lymphocytes for the major classes of GAG (i.e. hyaluronic acid, chrondroitin sulfates, heparin), but lymphocytes bind heparin much more avidly than other GAG species. Analysis of the binding of solubilized radiolabelled cell-surface molecules to immobilized GAG revealed cell-type specific expression of GAG-binding molecules. Thus, each of four lymphoma cell lines tested gave a characteristic pattern of GAG-binding molecules, some molecules being unique to a particular cell line and others being shared by some of the lines. Similarly, splenocytes expressed at least 10 distinct GAG-binding molecules with molecular weights (MW) ranging from 10,000 to 100,000, whereas thymocytes expressed additional GAG-binding proteins of 190,000 and 250,000 MW. Furthermore, splenocytes differed from thymocytes by possessing a unique family of cell-surface molecules which reacted with each GAG. Immunoprecipitation studies demonstrated that the GAG-binding molecules on splenocytes did not correspond to any of the cell-surface antigens tested, notably the cell adhesion molecules MEL-14, CD11/CD18 and CD44, although CD8 bound weakly to heparin. Four lymphoma cell lines with well-characterized migration properties were examined for GAG-binding molecules which may control lymphocyte migration. It was found that no one GAG-binding protein could be correlated with the entry of cells into a particular lymphoid organ. Nevertheless, the role of GAG-binding molecules in the subsequent positioning of lymphocytes within lymphoid organs requires further investigation. [ABSTRACT FROM AUTHOR]

This paper describes the induction of immunosuppression by multiple injections of carrageenan-lambda (cgn) in BALB/c mice. While cgn alone induced non-specific suppression that persisted for up to 25 days, priming with sheep red blood cells (SRBC) of mice within l0 days of cgn treatment prolonged the suppressive state. Also, antigen (SRBC)-specific suppression was observed when these mice were siren a secondary challenge 25–30 days after priming. Thus multiple cgn treatment along with priming SRBC generated non-specific and specific suppressive states which were transferable by Thy-l+ Lyt-2+ splenocytes. [ABSTRACT FROM AUTHOR]

The mechanisms which generate heterogeneity amongst resident tissue macrophages (Mø) are poorly understood. In a previous study we described a novel mouse Mø haemagglutinin, which binds unopsonized sheep erythrocytes. This sheep erythrocyte receptor (SER) is expressed at high levels on stromal Mø from bone marrow and lymph nodes, but at low levels on Mø from serous cavities and broncho-alveolar spaces. In this paper we demonstrate that a species-restricted factor in mouse serum is required in vitro for optimal maintenance of SER on resident bone marrow Mø and for its induction on Mø populations which normally lack this receptor. Using thioglycollate-elicited peritoneal Mø, induction of SER by mouse serum was doses dependent, reached maximal levels by 3- 4 days, required the continuous presence of mouse serum, and was fully reversible. Reexpression following trypsinization was inhibited by cycloheximide, showing that protein synthesis by Mø was necessary. Using a quantitative microtitre plate assay to measure levels of the inducing activity (SER-IA) in different samples, it was found to be heatelabile, non-dialysable, precipitable by polyethylene glycol and inactivated at pH 4 but not at pH 96. On gel filtration of mouse serum, a single major peak of activity was obtained with an apparent MW of around 70,000. SER-IA appears to be unrelated to a variety of factors and cytokines which affect Mø function, including colony-stimulating factors I (CSF-1). The possible role of SER-IA in regulating the differential expression of SER in vivo is discussed. [ABSTRACT FROM AUTHOR]

This paper describes some of the characteristics of a suppressor cell which is capable of regulating a rat RBC-induced autoantibody response against mouse RBCs. This cell, which appears to function as an inducer of suppression on transfer to naive recipients, is sensitive to Iow doses of cyclophosphamide, and its generation is affected by iow doses of irradiation. However, the recipients of these cells arc insensitive to cyclophosphamide treatment, suppression still being induced in such animals. [ABSTRACT FROM AUTHOR]

A comparative study has been made of human precipitating and co-precipitating anti-tetanus toxin antibodies. IgO co-precipitating antibody represented 10% of the total antibodies in the serum and had immunological and biological properties similar to those described for co-precipitating antibodies of other animal species. Human precipitating and co-precipitating anti- bodies had the same electrophoretic mobility and were localized in the same immunoglobulin fraction. By immunoprecipitation it was not possible to find antigenic differences between precipitating and co-precipitating antibodies. Both antibodies were localized in the IgG1 and IgG3 subclasses and neither were in the IgG4 subclass. Only the precipitating antibody can form insoluble complexes with antigen. Precipitating and co-precipitating antibodies agglutinated sensitized sheep red cells, however, only the precipitating antibody agglutinated human red cells. Eight to ten times more co-precipitating antibody was required to obtain a positive reaction in PCA. Precipitating antibody activated the complement system while co-precipitating antibody lacked this capacity. This difference in behaviour could not be attributed to localization of both antibodies in different IgO subclasses. Precipitating and co-precipitating antibodies were cytophilic. Only the former activated phagocytosis and increased clearance of antigen from the blood. These results are not surprising since co-precipitating antibody does not fix complement. Competition between human precipitating and co-precipitating antibodies in opsonization was analysed. In this test competition of both antibodies for the antigen depends on their respective amounts The K= 0.18 diminished to 005 when the ratio of pp:cop. antibody changed from 10:30 to 30:70. The fact that co-precipitating antibody was isolated from the sera of vertebrates other than man indicate that this antibody could possibly play a role in some immune mechanisms. Taking into account that in previous papers we have demonstrated that co-precipitating antibody functions as a molecule with one combining site of high affinity and one of low affinity, we have proposed that this antibody could function univalently and blocks the antigen. This could facilitate chronic parasitic, bacterial and viral infections, tumour growth and other chronic infections. [ABSTRACT FROM AUTHOR]

Murine lymphocytes spontaneously bind autologous and allogeneic erythrocytes via receptors that primarily recognize self H-2L molecules on the erythrocyte surface. Normal mouse serum contains a factor, termed autorosette inhibition factor (AIF), that very effectively blocks autorosette formation. This paper describes experiments that determine the origin and nature of serum AIF. It was found that AIF lacks strain and species , serum from several mammalian and nonmammalian species inhibiting the autorosetting of BALB/c thymocytes. However, mouse strains differed in the levels of AIF in their serum. Furthermore, AIF appears to directly interact with autorosetting roceptors on lymphocytes as thymocytes from the BALB/c-H-2dm2 mutant strain, which lack autorosetting receptors, were unable to absorb the factor. Several lines of experimental evidence indicated that AIF is secreted by a population of short-lived, radiosensitive macrophages (or monocytes). Firstly, in vivo administration of the anti-macrophage agents carrageenan and silica profoundly depressed AIF levels in serum. Secondly, in vitro culturing of different lymphoid cells revealed that AIF is secreted by an adherent population of peritoneal cells. Thirdly, total body irradiation experiments demonstrated that AIF production is dependent upon a radiosensitive cell that is bone marrow derived. Finally, AIF was purified to homogeneity from mouse plasma and shown to be a single polypeptide chain with a molecular weight of 84,000. [ABSTRACT FROM AUTHOR]

Bovine peripheral blood monocytes were isolated from bully coats of ACD-anticoagulated whole blood. Cells cultivated on plastic surfaces for 20 h were judged to be 95% thonocytes based on non- specificesterase-l staining, uptakeoflatexparticlesand surface receptor characteristics. Bovine monocytes were maintained up to 80 days in vitro in Dulbecco's modified Eagle medium with 15% horse serum and 15% foetal bovine serum. Several morphological and physiological features of bovine monocytes were examined during the course of culture. Cell size and cytoplasmic spreading, granulation and vacuolization increased progressively. Multinucleated giant cells pre- dominated during the latter stages of in vitro culture A high percentage of bovine monocytes possessed C3 and IgU Fc receptors, whereas 1gM Fc and sheep erythrocyte receptors were not detected. Phagocytosis was mediated by the IgG receptor, but not by the C3 receptor. Peroxidase activity declined in a linear fashion, with cells essentially negative after 8 days of culture. Total cell protein and acid phosphatase increased during cultivation. Lysozyme activity was undetectable in both lysates and supernatants of bovine monocyte. These findings are consistent with the concept of maturation of mononuclear phagocytes. The procedures for isolation and cultivation described in this paper will provide methodology for detailed study of bovine mononuclear phagocytes. [ABSTRACT FROM AUTHOR]

Plaque-forming cell responses and antibody titres to sheep red cells (SRC) were elevated in normally-fed irradiated adult mice reconstituted with spleen cells from young mice which had received a 4% albumin diet, compared with those given cells from normally-fed littermates. This was independent of the dose of cells transferred (5 × 106-4 × 107), the day of assay (3–10) and the duration of protein-deficiency (1 or 3 weeks). It suggests that the depressed responses produced by protein-deficient (donor) mice reported in earlier papers resulted from an impairment of reticuloendothelial function or a shortage of protein reserves, not directly associated with the spleen. As protein-deficiency (of the donor) accelerated the initiation of the adoptive response and increased the cell yields of the recipients it is considered likely that an enhancement of cell proliferation during the first 3-5 days after transfer was responsible for the elevated responses. [ABSTRACT FROM AUTHOR]

This work concerns the involvement of brown adipose tissue in the immune system of the rat. Wistar rats were thymectomized, adipectomized (surgical extirpation of the interscapular brown adipose tissue), thymectornited and adipectomized, and. sham,operated at birth, only 8-week-old females being employed in the experiment The production of antibody to bovine serum albumin (BSA). and sheep red blood cells (SRBC), delayed skin reactions to BSA, rejection of thyroid allograft implanted under the kidney capsule, and development of experimental allergic encephalomyelitis were investigated. Neonatal adipectomy did not affect the production of anti-BSA and anti-SRBC antibodies. On the other hand, delayed skin reactions to BSA, rejection of thyroid allograft, and incidence and severity of allergic encephalomyelitis were much more pronounced In adipectomized animals. It has been postulated that the immune function of brown adipose tissue is an expression of the secretory activity of the tissue. Since the immunosuppressive effect of neonatal thymectomy on demyelinating disease was neutralized by neonatal adipectomy, and vice versa, and since thymectomy rendered ineffective the immunopotentiating influence of adipectomy on this disease, as demonstrated in thymo-adipectomized rats, it was concluded that the brown adipose tissue is a natural antagonist of the thymus in cell-mediated immunity. This paper also describes the extra thymuses which were situated in the vicinity of the thyroid and parathyroid lobes of 23.2 per cent of rats. [ABSTRACT FROM AUTHOR]

To explore the mechanisms of antigenic competition, immunological and histological studies were made on mice using non-crossreacting heterologous erythrocyte antigens, i.e. sheep (SRBC), horse (HRBC) and chicken (CRBC) erythrocytes. Deficiency in the competition-inducing capacity of CRBC which we demonstrated in a previous paper was corroborated by the results that under any experimental conditions examined CRBC were unable to induce the competition. Of interest in the studies was that when anti-HRBC antibody responses of mice pre-injected with SRBC, i.e. competing antigen, were examined on day 2 and day 4 of HRBC-immunization, the day-2 response was revealed to be significantly enhanced, whereas the day-4-response was markedly suppressed as a result of the antigenic competition. By contrast, pre-injection with CRBC, i.e. non-competing antigen, did not affect at all either day-2 or day-4 anti-HRBC response of mice. Histological features of the spleens of mice either being prepared for antigenic competition or undergoing competitively suppressed antibody response were characterized by prominent regeneration of hyperplastic germinal centres, involving appearance of numerous tingible bodies and distinct collars of small lymphocytes which suggested massive proliferation and degeneration of lymphocytes. The spleens of mice in the immunological state indifferent to antigenic competition were characterized by huge lymphatic follicles which contained very few tingible bodies and were circumscribed by a markedly attenuated zone of small lymphocytes. From all these results, we suggest that massive proliferation and differentiation of T lymphocytes, probably toward regulatory (suppressor) T cells, could account for a mechanism of antigenic competition, and that deficient competition-inducing capacity of CRBC should be ascribed to weakness of their capacity in activation of the regulatory T lymphocytes.

Non‐immune cells are increasingly recognized as important in regulating immunity, but the role of red blood cells (RBC) remains relatively unexplored, despite their abundance in the circulation and a cell surface rich in potential ligands. Here, we determine whether RBC influence the activation state of human B cells. Separation of RBC from peripheral blood mononuclear cells increased B‐cell expression of HLA‐DR/DP/DQ, whilst reconstitution reduced the levels of B‐cell activation markers HLA‐DR/DP/DQ, CD86, CD69 and CD40, as well as decreasing proliferative responses and IgM secretion. Inhibition of B cells required contact with RBC and was abrogated by either removal of sialic acids from RBC or blocking the corresponding lectin receptor CD22 on B cells. Chronic lymphocytic leukaemia B cells express low levels of CD22 and were less susceptible to inhibition by RBC, which may contribute to their activated phenotype. Taken together, the results identify a novel mechanism that may suppress inappropriate responsiveness of healthy B cells whilst circulating in the bloodstream. [ABSTRACT FROM AUTHOR]

The reactivity of mouse antibodies against bromelain-treated mouse erythrocytes (BrMRBC) with mouse platelets before and after thrombin treatment was assessed by flow cytometry. Anti-BrMRBC antibodies could bind to thrombin-treated platelets, although normal platelets were also weakly reactive with the antibodies. The binding of anti-BrMRBC antibodies to platelets was confirmed by complement-dependent lysis. It is suggested that thrombin-activated platelets may be a real target for anti-BrMRBC antibodies. [ABSTRACT FROM AUTHOR]

It is widely accepted that antibodies and CD4 T cells play critical roles in the immune response during the blood stage of malaria, whereas the role of CD8 T cells remains controversial. Here, we show that both CD8 and CD4 T cells robustly responded to an acute self-limiting blood-stage infection with Plasmodium yoelii. Similar to antigen-specific T cells, both CD8 and CD4 T cells showed dynamic expression of the surface proteins interleukin (IL)-7R and programmed death-1 (PD-1). Additionally, activated CD8 T cells showed differences in the expression of Killer cell lectin-like receptor G1, L-selectin and B cell lymphoma-2 and produced granzyme B, indicating cytotoxic activity, and the initially high expression of T-box transcription factor TBX21 in malaria-activated CD4 T cells indicated an early T helper type 1 (Th1)-skewed immune response. Our data demonstrate that blood-stage malaria infection results in a striking T-cell response and that activated CD8 and CD4 T cells have phenotypic and functional characteristics that are consistent with conventional antigen-specific effector and memory T cells. Therefore, a better understanding of the CD8 and CD4 T-cell response induced by blood-stage infection may prove to be essential in the development of a vaccine that targets the erythrocytic stage of the malarial parasite. [ABSTRACT FROM AUTHOR]

We sought to characterize factors released by sonicated human erythrocytes that stimulate peripheral blood mononuclear cells (PBMNC) to release tumour necrosis factor-α (TNF). This response is not inhibited by polymyxin B, indicating that contaminating lipopolysaccharide (LPS) is not responsible. When erythrocyte lysates are fractionated by reverse-phase chromatography using a gradient of n-propanol on Sep-Pak® C18 cartridges, the TNF-inducing activity elutes as a single peak. The erythrocyte-derived TNF-inducing activity is unaffected by digestion with proteases but is destroyed by mild base hydrolysis or digestion by lipases, indicating that compounds containing ester-linked acyl chains may be essential. These properties are similar to those of TNF stimulators that we have previously identified in erythrocytes infected with malaria parasites, except that the TNF-inducing activity per cell is about 200 times higher in parasitized erythrocytes than in uninfected erythrocytes. Lipase-digested erythrocyte lysates inhibit the TNF- inducing factors of both normal and malaria-infected erythrocytes, suggesting that lipase digestion creates partial structures which compete with active components for macrophage receptors. Such receptors may recognize a common structure that contains an inositol monophosphate (IMP)-like component, as IMP also inhibits the TNF response to erythrocyte-derived factors and to parasite lysates whereas it does not affect the response to LPS. We conclude that lysed erythrocytes release specific cytokine-inducing factors that may contribute to the fever response to non-infectious tissue injury. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that the treatment of neutrophils with [roteolytic enzymes markedly reduces the expression of receptor III for the Fc portion of IgG (FcγRIII), but it does not affect the number of FcγRII on the cell surface. In the present study, we analysed the effect of proteolytic enzymes on functional responses of neutrophils induced by immune complexes (IC). Our results showed that treatment with pronase or chymotrypsin markedly increased the binding of IgG-coated erythrocytes (IgG-E) to neutrophils, as well as their capability to display IgGmediated functions such as antibody-dependent cellular cytotoxicity (ADCC) and chemiluminescence (CL) induced by IgG-E, responses that have been shown to be completely dependent on FcγRII. A similar enhancing effect was observed, in all cases, after neutrophil treatment with neuroaminidase. We also studied the effect of proteolysis on neutrophil activation induced by other types of IC. It was found that pronase and chymotrypsin significantly enhanced CL responses induced by soluble IC (sIC) but did not modify the responses induced by either precipitating IC (pIC) or soluble IC prepared with cationized antibodies (catIC). On the other hand, neuroaminidase significantly enhanced CL induced by either sIC, pIC or catIC. Taken together, our data suggest that the activity of FcγRII can be up-regulated by proteolysis. However, this effect appears to be strongly dependent on the characteristics of the IC employed as stimulus. [ABSTRACT FROM AUTHOR]

An inhibitor of the membrane attack complex of complement was isolated from the membranes of sheep erythrocytes. Fast protein liquid chromatography (FPLC) and affinity purification procedures for this sheep complement-inhibiting protein (SCIP) both yielded a pure protein with an apparent Mr of 19,000 under reducing and non-reducing conditions. Incubation of the denatured protein with neuraminidase and Endo-F reduced the apparent Mr to 18,000 and 15,000 respectively, while treatment with O-deglycosidase or phosphatidylinositol-specific phospholipase C (PIPLC) did not affect the apparent MrSCIP was detectable on erythrocytes and lymphocytes but not on platelets and could partially be removed by PIPLC treatment. Deglycosylation of the pure protein markedly reduced and PIPLC treatment abolished its activity. A monoclonal antibody (mAb) raised against sheep complement-inhibiting protein (SCIP) enhanced the susceptibility of sheep erythrocytes to lysis by homologous complement. SCIP inhibited complement after the stage of C5b-7 formation. Amino terminal protein sequence was obtained and was shown to be similar to that human CD59. All these features suggest that SCIP is the sheep equivalent of human CD59. Human CD59 has been reported to be species in that it inhibits complement from relatively few species. However, SCIP efficiently inhibited lysis of guinea-pig erythrocytes by complement from a wide range of species tested indicating that it is a potent and non-selective inhibitor of the membrane attack complex of complement (MAC). [ABSTRACT FROM AUTHOR]

The primary IgM response of murine B lymphocytes against red blood cell-bound antigens can be induced by incubating antigen-reactive B cells either with the lymphokines interleukin-1 (IL-1) and IL-2 together with the nucleoside cAMP, or by the addition of antigen-specific helper T cells. The reactivity of B cells is strongly influenced by the T-cell lymphokine IL-2. IL-2 inhibits the cyclic adenosine 3',5'-phosphate (cAMP)-dependent B-cell response when it is allowed to act on the cells prior to cAMP. On the other hand, if IL-2 acts on B cells together with or after cAMP, it synergizes with the nucleoside and enhances the immune response. A similar effect of IL-2 is observed in the Tcell-mediated activation of B cells. If IL-2 is present before helper T cells interacted with B cells, it inhibits antibody production. The inhibitory IL-2 effect is reversed by the simultaneous addition of exogenous cAMP. The finding supports the hypothesis that Ia ligation by T cells results in B cells in the elevation of cAMP which acts as an important second messenger in B cells. The antagonism between cAMP and IL-2 was also examined in the pre-B-cell line 70Z/3. The nucleoside is highly toxic to 70Z/3 pre-B cells and a majority disintegrates within hours of exposure to the nucleoside. The surviving cells undergo phenotypic differentiation expressing surface Igκ chains and major histocompatibility complex (MHC) class II molecules, and increase the expression of IL-2 receptor (R). The phenotypic differentiation requires the presence of IL-1. IL-2 inhibits both of these B-cell responses to cAMP, the IL-1-independent cell death, and the IL-1-dependent phenotypic differentiation. [ABSTRACT FROM AUTHOR]

The present study focused on the influence of maternal immunity during pregnancy on the responsiveness of the immune system(s) in offspring. Maternal immunization of pregnant mice with T-dependent foreign antigen sheep red blood cells (SRBC) induced suppression of anti-SRBC plaque-forming cell (PFC) responses in their offspring. We attempted to identify the cell species among the maternal lymphoid cells of the immunized pregnant mice that induced this suppression in their offspring, by separating the maternal cells into T cells, B cells and macrophages, or T-cell subsets, and then adoptively transferring them into other normal pregnant mice. The results demonstrated the following: first, maternal CD4+ T cells of immunized pregnant mice induced immune suppression in their offspring. Second, maternal T cells could be activated during pregnancy in the same fashion as in non-pregnant mice. The T-cell factor(s) for the immune suppression in offspring is produced not only by maternal T cells of immunized pregnant mice but also by T cells activated in non-pregnant mice. Third, cellular organization was required for maternal T cells to induce this immune suppression in their offspring. [ABSTRACT FROM AUTHOR]

CD59 is a widely expressed cell surface glycosylphosphatidylinositol (GPI)-linked glycoprotein which acts as an inhibitor of the assembly of the membrane attack complex of autologous complement. Four new monoclonal antibodies to CD59 (2/24, 1B2, BRIC 229, BRIC 257) are described. Competitive binding experiments using these antibodies, two known CD59 antibodies (MEM-43, YTH 53.1) and a previously described antibody LICR-LON-Fib75.1 demonstrated that all seven antibodies see related epitopes on human erythrocyte CD59. In common with other GPI-linked proteins, CD59 (as defined by antibody 2/24) was sensitive to treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) on lymphocytes and monocytes but not on erythrocytes. Flow cytometric analysis using antibody 2/24 identified two populations (CD59 positive and CD59 deficient) of lymphocytes, monocytes and erythrocytes in peripheral blood from a patient with paroxysmal nocturnal haemoglobinuria (PNH). The abundance of CD59 on normal erythrocytes was determined as 21,000 copies/cell when radioiodinated BRIC 229 was used. Other CD59 antibodies gave values of 10,000 (IF5) and 15,000 (2/24) against the same target cells. Radioiodinated Fab fragments of BRIC 229 gave a value of 39,000 copies/cell. Erythrocytes from two individuals with a rare inherited deficiency of decay accelerating factor (DAF), known as the Inab phenotype, expressed normal levels of CD59. [ABSTRACT FROM AUTHOR]

CD5 (Ly-1) B cells are a minor subpopulation in mouse spleen and are thought to be responsible for the production of natural autoantibodies to bromelain-treated autologous erythrocytes (Br-RBC). Here it is shown that substantial numbers of conventional, CD5-negative, splenic B cells also secrete these antibodies in CBA and (NZB × NZW)F1 mice, whereas in NZB and BALB/c mice they are all produced by the CD5 B-cell population. However, stimulation with bacterial lipopolysaccharide in vivo preferentially activates the CD5 B-cell group to anti-Br-RBC antibody secretion. [ABSTRACT FROM AUTHOR]

The binding of 251-BSA-anti-BSA immune complexes (IC) formed in the presence of complement (nascent IC) and those that reacted with complement after their formation (preformed IC) to human erythrocytes was studied. The effect of antigen-antibody ratios and serum dilutions on IC binding to red blood cells (RBC) were also investigated. A dramatic difference was found between the behaviour of the two types of complexes: while preformed IC bound effectively to human RBC after their interaction with complement, no efficient RBC-binding was observed with nascent BSA-anti-BSA complexes formed in the presence of complement. Changing the antigen-antibody ratio or dilution of serum did not affect markedly the extent of difference between the binding of preformed and nascent IC. Our findings do not support the essential role of red blood cells in the elimination of each type of IC. [ABSTRACT FROM AUTHOR]

Agglutinating activity of the major serum lectin of Periplaneta americana against mammalian erythrocytes has been found previously to be inhibited most effectively by galactose and glycoproteins rich in non-reducing terminal galactose, such as porcine stomach mucin (PSM) and desialylated fetuin and bovine submaxillary mucin. Antibody raised against the purified lectin was found, by immunofluorescence, to bind to the surface of washed fixed haemocytes (the cells responsible for cellular immunity in insects). The experiments described here were carried out in order to investigate whether or not the lectin plays any role in mediating the haemocytic response, by measuring the in vivo cellular response to galactose- or sialic add-rich glycoproteins, either in solution or conjugated to Sepharose beads. Comparison of the ability of injected solutions to stimulate haemocytic aggregates (nodules) showed that PSM, whether native, desialylated or pronase-digested to produce small galactose-containing fragments, stimulated large numbers of nodules, in contrast to either sialic acid-rich glycoproteins such as bovine submaxillary mucin (BSM) and fetuin, or the protein bovine serum albumen (BSA). Multicellular capsules formed around Sepharose conjugated to galactose-rich molecules such as PSM, asialo-PSM, asialo-fetuin or asialo-BSM were highly significantly thicker than those formed around control untreated beads, whereas capsules around BSA, fetuin or BSM conjugates were significantly thinner. It is unlikely that the different results for sialylated and desialylated molecules are due merely to a non-specific charge effect, since the response due to charge alone is directly opposite to that found when specific carbohydrate groups are considered. The results tentatively support the idea that soluble and/or cell-associated lectins may be involved in immuno-recognition in insects. [ABSTRACT FROM AUTHOR]

In the present study we have investigated whether bovine erythrocytes (Eb) specifically sensitized with human polyclonal IgA l (EbIgA 1) are able to bind to resident adherent rat peritoneal cells (PMø). Rat PMø formed rosettes with Eb-IgAl at room temperature and at 37°. The formation of these rosettes could be blocked completely by excess human serum IgA or myeloma IgAl. In contrast, human IgG or rat IgG did not inhibit the formation of rosettes, whereas human polymeric myeloma IgA2 only partially inhibited rosette formation. Complete inhibition of rosette formation was also induced by rat monomeric and polymeric myeloma IgA, suggesting species interchangeability. Furthermore, rosette formation could be completely blocked in the presence of excess asialofetuin or D-galactose, while excess ovalbumin or D-mannose had no effect. These results suggest that the oligosaccharides in the hinge region of human IgAl are involved in the binding of Eb-IgAI to rat PMø. [ABSTRACT FROM AUTHOR]

The Ina and Inb blood group antigens were found to he located on an erythrocyte membrane glycoprotein of 80,000 MW by immunoblotting with human anti-Ina and anti-Inb antibodies under non-reducing conditions. This glycoprotein is shown here to be identical to that defined by monoclonal antibodies to CDw44, and a new murine monoclonal antibody (BRIC 35) is added to this cluster. Experiments with endo-β-galactosidase and Endo F preparations suggest that the glycoprotein contains one or more N-glycans but that these oligosaccharides do not contain extensive poly-N-acetyl lacto saminyl sequences. Experiments using membranes prepared from sialidase-treated normal erythrocytes, from Tn erythrocytes and from Cad erythrocytes suggest that the glycoprotein does not contain a substantial content of O-glycans, The Inb antigen and the epitope defined by a murine monoclonal antibody (BRIC 35) show reduced expression on Lu(a-b-) erythrocytes which result from the effect of the dominant inhibitor gene In(Lu). Evidence is presented here that the Inb antigen is expressed on normal granulocytes and lymphocytes and on the haemopoietic cell lines HEL, K562 and HL-60, a lymphoblastoid cell line and lymphocytes from two patients with B-CLL. [ABSTRACT FROM AUTHOR]

A new human erythrocyte glycoprotein has been identified by immunoblotting with murine monoclonal antibodies under non-reducing conditions. The glycoprotein has a MW of 70,000 and carries Cromer-related blood group antigens. The monoclonal antibodies also react with normal peripheral blood leucocytes and platelets and several haemopoietic cell lines. The glycoprotein has a reduced MW after sialidase treatment. The MW is markedly reduced in Tn erythrocyte membranes and slightly increased in Cad erythrocyte membranes. These results suggest that the glycoprotein has a substantial content of O-glycans. The glycoprotein appears to be absent from, or grossly altered in, the erythrocytes of two individuals with the rare Inab phenotype. [ABSTRACT FROM AUTHOR]

Immunoglobulin G (IgG) provides an efficient acceptor site for nascent C3b, and complement activation on the surface of IgG-coated bacteria has been shown to generate significant numbers of C3b-IgG complexes. We have studied the relative efficiency of IgG alone, C3b-IgG complexes, and similar densities of IgG and C3b residues deposited independently, in mediating ingestion of sheep erythrocyte (E) targets by human phagocytes. Human 125I-C3b covalently bound to rabbit anti-Forssman IgG was generated as described elsewhere (Fries et al., 1985). E, EIgMC4b, or EIgMC4b3b (prepared with IgM antibody and purified complement components) were sensitized with radiolabelled anti-Forssman IgG or C3b-IgG heterodimers to generate targets beating IgG alone, C3b-IgG covalent complexes, or C3b and IgG in equivalent numbers but not bound to each other. Phagocytosis by monocytes and polymorphonuclear leucocytes (PMN) of targets bearing C3b-IgG was markedly enhanced relative to those bearing IgG alone, especially at levels of < 2000 opsonin residues/target cell. Uptake of C3b-IgG-hearing targets was also significantly more resistant to competitive inhibition by ambient monomeric IgG. Phagocytosis of EIgMCAb+C3b-IgG by monocytes was superior to the uptake of either EAC4b + IgG or EAC4b3b + IgG bearing equivalent amounts of C3b and IgG not in covalent complex (P < 0·05, n = 10). Similar results were obtained with PMN Thus, generation of C3b-IgG complexes in vivo may not only promote complement activation and enhance C3b deposition, but also produce a compound opsonic residue which is a more potent promoter of phagocytosis than an equal number of C3b and IgG residues randomly distributed relative to each other. [ABSTRACT FROM AUTHOR]

The effects of immune complex infusion on the clearance of antibody (R3/13)-coated and NEM- treated rat erythrocytes by the splenic component of the rat mononuclear phagocyte system (MPS) were investigated. Equivalence complexes of USA-anti-BSA produced a significant delay in the clearance of the NEM cells (pre-infusion T½ 19.7± 3.9 mm, post-infusion T½ 26.5 ± 3.8 min, mean ± SE, n = 6, P < 0.01), but this effect could be abolished by agents that prevented the changes in the splenic blood flow that followed complement activation. The immune complexes formed in 10- fold antigen excess (mean size 1 5S) did not delay the clearance of the NEM cells. Clearance of R3/13- coated cells was impaired by the infusion of immune complexes prepared at equivalence, 10-fold antigen excess or complexes prepared with F(ab')2 fragments of rabbit anti-USA antibody. The inhibition of red cell clearance was independent of changes in blood flow, but the degree of inhibition produced did not correlate well with the dose of immune complex injected. [ABSTRACT FROM AUTHOR]

The splenic component of the mononuclear phagocyte system (MPS) was investigated in the rat using N-ethylmaleimide-treated erythrocytes (NEM) and erythrocytes coated with a monoclonal IgG2b antibody (R3/13) directed against the rat RTIAa major histocompatibility antigen. Both cell suspensions were removed by the spleen, and their clearance times were significantly longer in splenectomized animals. The mean clearance times for the NEM-treated cells in both normal and cobra venom-treated rats were similar (19.1 ± 1.1 mm and 190± 10 mm, respectively) but differences were seen between the clearance of R3/13 antibody-sensitized cells in these two groups (normal rats 38.3 ± 2.8 mm and CVF-treated rats 51.7± 4.2 mm, P< 0.02). Different receptors were also involved in the removal of these cells; in normal animals recognition entailed interaction with complement receptors, whereas in CVF-treated animals this was implemented by Fc receptors. Complement activation prolonged the clearance rates of both R3/1 3 cells and NEM cells in normal animals, but the effect of complement activation on the clearance of NEM-treated cells was achieved via changes in splenic blood flow. When this was prevented from taking place no effect was seen on the clearance of NEM cells, although the clearance of R3/13 cells was inhibited by the complement fragments generated by complement activation. [ABSTRACT FROM AUTHOR]

Complement-mediated lysis of mouse erythrocytes (MRBC) by whole pigeon antisera was found to occur in the presence of magnesium ions alone. The underlying basis for this observation was demonstrated to be the ability of IgM antibodies to activate the alternative pathway of pigeon complement, whereas IgG activates a calcium-dependent pathway possessing an unusually low lytic capacity. In addition to differing from the alternative pathway by requiring both calcium and magnesium ions, the calcium-dependent pathway exhibited higher activity at low temperature and more rapid kinetics of haemolysis. The presence of early acting Cl in pigeon serum was inferred by the selective depletion of calcium-dependent activity which occurred as a result of incubating serum containing only calcium ions with MRIC sensitized with IgG. Under the same conditions, MRBC sensitized with IgM failed to deplete complement activity, indicating that Cl does not participate in complement activation by this isotype. Interestingly, the calcium-dependent pathway detected in pigeon serum appears to more closely resemble the Cl-bypass pathway rather than the classical pathway of mammalian complement. [ABSTRACT FROM AUTHOR]

The 202.000 MW protein XC, which is distinct from C3 but is essential for antibody-dependent haemolytic activity against SRBC, was obtained from Xenopus plasma following polyethylene glycol precipitation, ion-exchange chromatography and gel- filtration. The protein required other components of the Xenopus serum in order to lyse sensitized SRBC, but did not lyse unsensitized RRBC through the alternative pathway. The protein, contained at 0.17 mg/ml in the original plasma, comprised three distinct subunits of 96,000, 76,000 and 26,000, which were linked by disulphide bonds. Digestion by trypsin resulted in a specific cleavage of the 96,000 subunit and a conversion of its immunoelectrophoretic mobility to the anodal side, leaving the 76,000 and 26,000 subunits intact. The treatment with SDS and urea resulted in the splitting of the 96,000 subunits into 48,000 and 45,000 components. but this splitting was inhibited upon pretreatment with methylamine, suggesting the presence of a thiol ester bond in the 96,000 subunit. The amino acid composition of the XC revealed a striking resemblance to that of human C3 and C4. We therefore conclude that the 202,000 protein isolated in this study represents the C4 which plays an essential role in the classical haemolytic pathway. [ABSTRACT FROM AUTHOR]

Rabbit red blood cells (RaRBC, 3 × 107/ml PBS) were incubated with different amounts of purified human C3 at 37 for 30 mm and washed twice in PBS. Different amounts of normal human serum containing 2 mM Mg2+ and 5 mM EGTA were added to the C3-treated and control RaRBC. The extent of lysis was measured after a further incubation at 37 for 40 mm. Enhanced lysis was observed with C3-treated RaRBC as compared to control cells. The enhancing effect was dependent on the dose of C3 used for the treatment of RaRBC. Investigating the kinetics of lysis. the lag phase was observed to be significantly shorter with the C3-treated than with the control RaRBC. No enhancement was found when RaRBC were pretreated with preformed C3b fragment. KSCN-treated C3 (C3b-like C3), however, had a lysis- enhancing effect. These results suggest that non- covalently bound C3 molecules may have a role in the initiation and/or maintenance of the alternative path- way activation on activator cells. [ABSTRACT FROM AUTHOR]

When normal mice are immunized with rat RBC, autoantibodies to mouse red cells and antigen-specific suppressor cells are generated. Suppressor cell activity is found in T-enriched populations and suppresses only the induction of autoantibody, not ongoing or secondary autoantibody responses. Using anti- bodies lytic for either B cells or distinct T-cell subpopulations, we are able to show that suppression is dependent on the presence of Lyt 1 + T cells. [ABSTRACT FROM AUTHOR]

The relative radiosensitivities of precursor (Tsp), activated (Ts) and memory (Tsm) suppressor T cells for delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) were investigated in mice. Spleen cells from CBA mice, primed i.v. with 109 SRBC 3–4 days previously, contain specific Ts cells which substantially impair the induction of DTH to SRBC in normal syngeneic recipients. Exposure of mice to 400 rad irradiation 1 day before the priming completely eliminated the subsequent development of Ts cells. In contrast, 3 days after the priming injection, Ts cell activity in mice is resistant to doses higher than 600 rads. Mice primed 40 days previously with 109 SRBC contain Ts-cell memory which can be readily recalled by i.p. injection of 108 SRBC, The secondary Ts cells which specifically inhibit DTH induction can be demonstrated adoptively in normal recipients. Mice were exposed to various doses of irradiation 40 days after the priming and 1 day before the i.p. injection, Ts memory was significantly reduced by 300 rads and was completely abrogated by 400 rads. The relative radiosensitivities of the three subsets of suppressor T cells are in the order of Tsm = Tsp > Ts. [ABSTRACT FROM AUTHOR]

Either alone or in combination with antibodies having specificity for the carrier erythrocyte, TNP-ORBC were injected i.p. into CBA/J mice. Five days later, their spleens were removed and evaluated for TNP-specific PFC. The spleens from animals receiving 19S antibody (IgM) with carrier specificity displayed 3-A-fold more direct and indirect hapten-specific PFC than control animals receiving the TNP-erythrocyte conjugate only. Animals receiving 7S antibodies (IgG) with carrier specificity displayed very little change in their direct PFC response to the hapten. However, the indirect response to the hapten was suppressed as much as 16-fold by carrier specific IgG. Evaluation by haptenic inhibition of the relative avidity of the antibodies being secreted by these cells revealed the following: the relative avidity of antibodies secreted by indirect PFC in the spleens of animals receiving TNP-ORBC only was approximately 20-fold higher than antibodies secreted by the direct PFC. The 3-4-fold potentiation of the hapten-specific PFC response by carder-specific IgM antibody did not result in a change in relative avidity of direct or indirect PFC. IgG with carrier specificity did not change the relative avidity of the antibodies secreted by direct PFC having specificity for the hapten. However, evaluation of the remaining PFC in spleens from animals whose indirect hapten-specific PFC response had been suppressed by carrier-specific IgG revealed that the remaining PFC had a lower avidity than indirect PFC from animals receiving TNP-ORBC only. In other words, carrier-specific IgG selectively induced suppression of high avidity hapten-specific IgG antibody secreting cells. [ABSTRACT FROM AUTHOR]

Hybridomas secreting anti-mouse macrophage antibodies were obtained by fusing a routine plasmacytoma with lymphocytes of a rat immunized against mouse macrophages. An IgM, monoclonal antibody (3 A 35) reacted with mouse monocytes, macrophages and polymorphonuclear leucocytes. It did not bind appreciably to erythrocytes, platelets and unstimulated T or B lymphocytes. However, 3 A 35 bound to various murine T-derived leukaemic cells and to a small proportion of Con A-stimulated thymocytes. Cross absorption experiments confirmed the existence of a common antigenic determinant on macrophages and leukaemic cells. The possiblility that 3 A 35 identified a previously described antigen common to macrophages and normal or leukaemic T cells was investigated. The antibody was tested against thymocytes and macrophages of various mouse strains, some congenic for H-2 or Tla. The 3 A 35-detected antigen was found to be different from Ly5, Tla and Qa and did not represent a I-J encoded allotypic specificity. [ABSTRACT FROM AUTHOR]

Lymphocytes bearing receptors for the Facb fragment of IgG have been shown previously to be elevated in the peripheral blood of patients with rheumatoid arthritis. The generation of these cells and their possible functional role in immune regulation have been investigated in mice. Facb rosette-forming (Facb-R+) lymphocytes were found to be elevated in the spleens of mice mounting a secondary plaque-forming cell (PFC) response to sheep erythrocytes but not during the primary response. Splenic Facb-R-lymphocytes were also elevated when a cross-reacting antigen (goat erythrocytes) was used for the secondary immunization but not when a non-cross-reacting antigen (chicken erythrocytes) was used. Both primary and secondary immunization with bacterial lipopolysaccharide resulted in elevation of splenic Facb-R+ lymphocytes. Administration of antigen-specific Facb fragment in conjunction with antigen (calf erythrocytes) produced a suppression of the secondary PFC response. However, F(ab′)2 fragments produced no such effect. This suppressive effect was shown to be antigen-specific since administration of Facb fragment of anti-calf erythrocyte IgG had no suppressive effect on the secondary PFC response to sheep erythrocytes. No change in splenic Facb-R+ lymphocytes was observed during delayed hypersensitivity responses to either sheep erythrocytes or the contact-sensitizing agent oxazolone. These results indicate that Facb-R+ lymphocytes are generated during secondary humoral responses bat not cell-mediated immune responses, and suggest that these cells may exert a suppressive influence on antibody production. These findings are discussed in relation to the occarrence of these cells in patients with rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

In this study we followed the in vivo fate and distribution of hapten-coupled sheep red blood cells (TNP-SRBC) coated with 125I-labelled anti-hapten antibody in mice. The majority of these complexes was rapidly taken up by the liver, and by macrophages in the marginal zone of the spleen. Within a few hours, however, marginal zone labelling diminished and label appeared in the corona of lymphoid follicles. After 1–7 days the only remaining label was associated with areas of follicular dendritic cells This follicular trapping was abolished by decomplementing mice with cobra venom factor. These results, therefore, demonstrate that immune complexes made with a large, particulate autigen are retained for long periods in lymphoid follicles in an analogous fashion to soluble complexes. We assume (but have not proved) that the complexes retained by dendritic cells contain soluble erythrocyte antigens released from macrophages, rather than intact RBC. This possibility is strengthened by the presence of significant amounts of free, functional antibody in the circulation of mice given TNP-SRBC coated with antibody in vitro. The possible significance of immune complex trapping in antibody-induced suppression of anti-RBC responses is discussed. [ABSTRACT FROM AUTHOR]

The isoelectric heterogeneity of both IgM and IgG murine anti-sheep red cell serum antibodies has been examined using an adaptation of published methods. It was found that the IgM spectra were restricted in a characteristic manner, implying oligoclonality. In cell transfer experiments, the T cell dependency of the IgM responses was confirmed. Further, helper cells appeared to switch on IgG antibody production and, simultaneously, recruit many novel IgG-forming clones into the response. The pattern of the IgM oligoclonality was attributed in part t o the inheritance of genes at, or closely linked to, the Ig1 heavy chain locus. These findings are discussed in relation to current research on the regulation of diversity. [ABSTRACT FROM AUTHOR]

When SJL mice are hyperimmunized with rat red blood cells (RBC), tolerance to self is readily broken and these animals develop a high autoantibody response to their own RBC. However, these mice also fail to generate those antigen-specific suppressor cells which normally regulate this induced autoantibody response. [ABSTRACT FROM AUTHOR]

Incorporation of lipid A into liposomes markedly enhances the plaque-forming cell (PFC responses against model membranes that are sensitized with synthetic amphipathic antigens 2,4-dinitrophenyl-6-N-aminocaproyldipalmytoylphosphatidylethanolamine (DNP-Cap-DPPE) and fluorescein thiocarbamyldipalmytoylphosphatidylethanolamine (FI-DPPE). The enhancing effect was pronounced only when lipid A and haptenic determinants were presented on the same liposome. Lipid A was incorporated into heterologous erythrocytes and syngeneic tumour cells. Significant and selective increase of in-vitro PFC responses was observed against heterologous erythrocytes, and immunization of C578L/6 mice with lipid A treated X-irradiated tumour cells (EL-4) markedly prolonged the survival of mice after challenge with homologous viable tumour cells. These data suggest that passively incorporated lipid A will be an effective method for selectively augmenting antibody formation against membrane-associated antigens. [ABSTRACT FROM AUTHOR]

Antigen-antibody complexes (Ag-Ab) prepared from 125I-bovine serum albumin (BSA) and guinea-pig anti-BSA were (i) incubated at 37° for 4 min with undiluted normal human serum and autologous red blood cells (RBC) together, or (ii) incubated first at 37° for 30 min with serum diluted optimally for binding and then with RBC. Reactions were stopped by dilution and cooling, and RBC bearing antigen-antibody-complement complexes (Ag-Ab--C) were washed and resuspended in either untreated normal human serum (undiluted or diluted), serum treated with zymosan (SZYM), ethylenediamine tetracetic acid (SEDTA) or ethyleneglycol tetracetic acid-Mg++ (SEGTA), serum heated at 56° for 30 or 120 min (SΔ30 or SΔ120), or buffer alone. The mixtures were placed at 37° and the percentage of Ag-Ab-C dissociated from RBC after progressively increasing times determined. (i) Ag:Ab:C bound to RBC with undiluted serum dissociated more rapidly following resuspension in SZYM, SEDTA, or SΔ30 than following resuspension in untreated serum. Rate of dissociation in SEGTA paralleled that in untreated serum. (ii) Ag-Ab-C bound to RBC with diluted serum dissociated following resuspension in SZYM, SEDTA, or SΔ30, but rebound and dissociated a second time following resuspension in untreated serum or SEGTA. Initial dissociation occurred in < min in undiluted serum, took place at 0° as well as 37°, and was diminished but detectable in >8- and > 64-fold- diluted serum, respectively. Rebinding required 37°, factors B and D and C3, and was maximal at 4-8 min. Subsequent dissociation had similar complement requirements to initial dissociation, but occurred only at 37° and was 90% complete at 15 min. No dissociation of Ag-Ab-C bound to RBC in (i) or in (ii) occurred following resuspension in SΔ120 or in buffer. These findings suggest that after initial binding, release of experimental immune complexes from RBC in whole serum involves concurrent dissociation and alternative pathway-dependent rebinding. [ABSTRACT FROM AUTHOR]

Cells bearing alien surface antigens can be specifically destroyed by antibodies directed to the antigens and certain Fc receptor-bearing lymphoid or monocytoid cells through a killing mechanism known as antibody-dependent cellular cytotoxicity (ADCC). The present study was undertaken to see if lectins could substitute for specific antibody in ADCC and initiate lysis of non-antibody-coated erythrocytes. Human peripheral blood leucocytes and mouse PU-5 monocytoid cell lines were used as effector cells. Target-cell destruction was measured by the specific release of 51Cr. Our data indicated that Wheat-germ agglutinin (WGA), but not concanavalin A or soybean agglutinin, could activate killing of non-antibody- coated erythrocytes by human peripheral blood leucocytes and PU-5 cells. The membrane structure on the effector cell that was triggered by WGA directly related to N-acetyl-glucosamine and may be adjacent to, if not part of, the Fc receptor. [ABSTRACT FROM AUTHOR]

DTH reactions to sheep erythrocytes (SRBC) and purified protein derivative (PPD) antigens were produced in the pleural cavity in mice. The profiles of the DTH reactions with respect to time course and cellular exudate reactions differed greatly according to the strains of mice. In particular, HY mice that were established in our laboratory displayed prolonged DTH reactions, characterized by macrophage followed by lymphocyte reactions. HY × C3H F1 mice showed a similar tendency. On the other hand, strains such as C3H, BALB/c, DBA/2 and B6 mice showed short-lived and macrophage-predominant DTH reactions. BALB/c nu/nu mice showed no DTH reactions. Characteristic features of the prolonged DTH reactions in HY mice were transferred with sensitized T cells. However, DTH reactions in HY mice treated with cyclophosphamide (CY) terminated in a short period, and mainly consisted of macrophages and polymorphs, although they were greatly enhanced. Such profiles of the reactions could also be transferred with sensitized T cells from CY-treated and SRBC-sensitized mice. Spleen cells taken from CY-treated and SRBC-sensitized HY mice, when injected intravenously into SRBC-sensitized HY mice just prior to challenge, could not interrupt prolonged DTH reactions. These results thus indicated various phenotypes of the DTH reactions in terms of time course and exudate cellular component involved might be carried by the specific effector T cells in each phenotype of the DTH reactions and could be induced using strains of mice and CY. [ABSTRACT FROM AUTHOR]

Approximately half of the rosettes formed by rabbit Ig+ lymphocytes (B cells) and anti-Ig-coated erythrocytes or glutaraldehyde-fixed bacteria are dissociated upon the addition of rabbit serum. Rabbit serum was fractionated and the rosette-dissociating activity was found in purified preparations of rabbit α1- and α2-macroglobulins. Studies designed to elucidate the mechanism of rosette dissociation suggested that the α-macroglobulins dissociated rosettes by causing the release or proteolytic cleavage of the membrane proteins complexed with the anti-Ig-coated particles. These data suggest that the α-macroglobulins may have a role in the interaction of B lymphocytes with particulate antigens. [ABSTRACT FROM AUTHOR]

Mice injected with rat erythrocytes produce erythrocyte autoantibodies and suppressor cells that specifically inhibit the autoimmune response without inhibiting the net production of antibodies against rat erythrocytes. Here it is shown that the suppressor cells bind preferentially to monolayers of rat erythrocytes rather than to erythrocytes from mice or sheep, Suppressor populations depleted of B cells, and cells that adhered to monolayers of rat erythrocytes, lost the ability to suppress the production of autoantibodies in normal mice injected with rat erythrocytes. In contrast, suppressor populations depleted of B cells and cells that adhered to sheep erythrocytes or mouse erythrocytes retained suppressor activity. From these results it is suggested that the regulation of autoantibody production by the suppressor cells in this model may be part of a normal system by which antibody responses to foreign antigens are regulated, and not a unique homeostatic mechanism by which harmful autoimmune responses are eliminated. [ABSTRACT FROM AUTHOR]

Angiotensin II (At II) has been shown to inhibit in vitro the IgG2a-mediated rosette formation of 51Crk-sheep red blood cells (SRBC) by provoked peritoneal macrophages (PM) at 10-5-10-6 M concentrations. The decreased rosette formation was associated with an increased phagocytosis. It was found that the enhanced rosette formation at 10-7 M hormone concentration was followed by diminished phagocytosis via Fcγ receptors (R). Processes mediated through FcµR were affected only after incubation with 10-5 M of At II. The attachment and subsequent phagocytosis through C3bR was markedly enhanced by At Il in a dose-dependent way. Thus, the relative phagocytosis (RP) through both FcRs was significantly enhanced by 10-5, i.e. by 10-5-10-6 M of At II, but lowered at 10-7 M hormone concentration. In addition, there was no RP enhancing effect of At 11 after preincubation with 10-5 M of indomethacin (IM), indicating the significance of prostaglandins (PG) in the hormone effect. The medium containing 5 mM of EGTA diminished both the RP enhancing and inhibiting effects of At II. The RP mediated by C3b was not affected by At II, IM or EGTA. The intracellular killing capability, measured by chromium release from Candida albicans, was not altered or even slightly diminished after At II treatment of PMs. [ABSTRACT FROM AUTHOR]

We have made a detailed investigation to determine which of the B-cell subsets could be stimulated by Staphylococcus aureus Cowan 1 bacterium (SpA CoI). B-cell subsets were separated from peripheral blood and tonsil lymphocytes by means of rosette formation with E, EAIgG, anti-immunoglobulin (Ig) conjugated ox erythrocytes (OE-anti-Ig), and Protein A conjugated OE (OE-Pro A) or by separation on a bovine serum albumin (BSA) discontinuous density gradient. The cells responding to SpA Col included E receptor negative (E-), C3 receptor positive (C3R+), and surface Ig positive (SIg+) B-cell subsets. Among these B-cell subsets, FcR- cells were more responsive than FcR+ cells. These B-cell subsets responded alone to SpA CoI and significantly proliferated, although they failed to respond alone to pokeweed mitogen (PWM) and Protein A of S. aureus (Protein A). Among the SIg+ B-cell subsets stimulated with SpA CoI, IgM+ and IgG+ B cells showed a marked response and IgA+, and IgD+ B cells showed much less response. Both Protein A receptor positive (Pro A · R+) and negative (Pro A · R-) cells responded well to SpA CoI. Fractionation of B cells on a BSA gradient revealed that comparatively small sized and denser B-cell subsets responded well to SpA CoI. From these criteria, it is suggested that B cells responding to SpA Col are capable of stimulating not only mature B cells, but can also stimulate immature B cells. [ABSTRACT FROM AUTHOR]