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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.

In the previous paper we showed that the immune response to sheep red cells (SRBC) was degenerate; serum antibodies showed increasing loss of specificity, signalled by cross-reactions with horse RBC (HRBC), with time after immunization and with hyperimmunization. In the present report we have analysed the role T cells may play in this process. To do this we studied the antibodies made by mice deprived of T cells by irradiation as well as those made by normal mice immunized with SRBC in distilled water, which was shown to depress the DNA synthetic response of T cells. In both instances the mice with fewer responding T cells made less antibody which could agglutinate HRBC than did the appropriate controls. This was true even when no difference in anti-SRBC titre was apparent. In addition we showed that the antibody made by mice with reduced numbers of T cells was less effective at passive suppression of the immune response to SRBC than was similarly titred (against SRBC) antibody made by normal mice. Thus, certain sub-populations of antibodies, normally made in response to SRBC, immunization, are particularly thymus dependent. We have discussed why we think they are those of particularly high affinity. [ABSTRACT FROM AUTHOR]

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.

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]

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]

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]

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]

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]

Red cells sensitized with naturally occurring or 'immune' fowl antibody were lysed by fresh fowl serum. This fowl complement could not be replaced by that of human, rabbit or guinea pig. Both naturally occurring and 'immune' antibodies to red cells in the mammalian species tested did not lyse with fowl complement. Lysis by fresh fowl serum of sheep red cells sensitized with mammalian antibody is due to the presence of naturally occurrent antibody to these cells in the fowl serum; the enhancement of this lysis by the mammalian antibody will be described more fully in the next paper. Naturally occurring antibody to sheep red cells present in turkey serum and 'immune' antibody to fowl red cells were not lytic with fresh turkey serum, with fowl complement, with guinea-pig complement or with any combination of these. Some properties of fowl complement are given. [ABSTRACT FROM AUTHOR]

Whilst the ability of isoantibodies to agglutinate mouse red cells in saline medium does depend in part upon the properties of the antibody molecules, the concentration of antigen upon the red cell and certain genetically determined properties of the cell surface are of even greater importance. The red cells of mice of any strain will give positive results in the human serum:dextran system whilst reactions in a saline medium are unusual. In this paper the term ‘incomplete antibody’ is used to denote antibodies that can only be detected in conjunction with other antibodies in the human serum:dextran system. The time of appearance of antibodies to homografts of an ascites sarcoma, an ascites leukosis and a solid mammary carcinoma has been studied. Incomplete antibody as defined above has been detected by two methods. In the blocking test incomplete antibody is allowed to react with red cells before contact with complete antibody, a positive result being observed as a fall in titre when the treated red cells are subsequently exposed to complete antibody. In the second type of test, the synergic test, incomplete antibody is mixed with suitably diluted complete antibody and fitrated against suitable red cells, a positive result being a significant rise in titre as compared with complete antibody mixed with normal serum. Antibodies produced by the antigen donors did not give significant blocking or synergic effects. Incomplete antibodies are sometimes detectible on the third day and with regularity on the fourth day. Antibodies ‘complete’ for A strain red cells may appear at any time from the fifth day onwards. There is sometimes a drop in fitre of varying duration on the sixth day. This corresponds with the commencement of marked inflammatory changes on the graft bed. The maximum titre is attained at about two weeks. Antibodies may disappear in under three months or persist as long as a year. The function of antibodies in homograft reactions varies with the target tissue. However, they appear before the onset of anatomical signs of homograff response regardless of the type of target cell. [ABSTRACT FROM AUTHOR]

This paper describes a method for simultaneous measurement of the accumulation of plasma protein and erythrocytes in skin reactions of hypersensitivity to bovine γ-globulin (BGG) and tuberculin PPD in the guinea-pig. The procedure consists in giving 125I-labelled plasma albumin and 51Cr-labelled autologous erythrocytes together by intravenous injection into guinea-pigs bearing skin lesions of allergic inflammation at different times and for different periods during the development of the skin reactions. Isotope accumulation in excised skin reactions is measured by scintillation counting at different stages during the evolution of hypersensitivity responses. Skin reactions of combined anaphylactic and Arthus hypersensitivity to BGG were characterized by pronounced increased vascular permeability principally in the first hour. In established 24-hour hypersensitivity reactions to both antigens (BGG and PPD) there was continuing accumulation of both plasma albumin and erythrocytes. During the development of the tuberculin reaction, an intermediate phase of isotope accumulation occurred between 6 and 9 hours after skin testing; serum transfer studies showed that this intermediate peak was not attributable to circulating antibody alone. These isotope tracer techniques were also applied to study vascular permeability in systemically transferred reactions of delayed hypersensitivity and in the vascular response to the intradermal injection of an inflammatory factor generated by antigen-activation of sensitized lymphocytes. It was concluded that isotope tracing provided objective and sensitive methods for analyzing microvascular responses in allergic inflammation. [ABSTRACT FROM AUTHOR]

This paper describes a form of red cell lysis differentiated from classical complement haemolysis by its occurrence in the absence of antibody on the cells and in the presence of EDTA. This type of haemolysis has been called reactive haemolysis. It is the result of the interaction, in the presence of red cells, of at least two serum factors called ‘reactor’ and ‘indicator’, respectively. Reactor only becomes active after incubation at 37° of serum with certain agents, notably antibody-coated bacteria, zymosan and agarose, in conditions similar to those required for complement activation. The potential for the formation of activated reactor could be demonstrated infrequently in healthy subjects but more frequently in sera from hospital patients. Activated reactor behaved as a protein sedimenting between 7S and 19S, and of α2-β1, electrophoretic mobility in agar. Indicator factors were present in all human sera studied, as well as in the sera of a number of mammalian species. They were demonstrable at high dilutions of the serum and required no prior activation for their action. They occurred maximally in the 7S fractions of serum proteins and migrated in the β2 position on electrophoresis. Reactive haemolysis was first observed and can most conveniently lie demonstrated in a red cell-agarose gel. It can also be demonstrated in the test tube following partial purification of activated reactor and indicator factors. Studies in the test tube indicated that a .soluble labile lytic factor was responsible for this type of haemolysis, [ABSTRACT FROM AUTHOR]

The studies reported here indicate that tanned red cells coated with a mixture of chromatographically purified ovalbumin and conalbumin give agglutination titres which are directly related to the amount of antibody (as meas- ured by quantitative precipitation) present against either of these antigens in mixed sera. With whole (unabsorbed) mixed sera, these coated cells record the titre of the major antibody present, whether this is anti-ovalbumin or anti-conalbumin. There was no evidence of greater sensitivity to anti-conalbumin. A trace of ovalbumin in a preparation of conalbumin used to coat cells is fully sufficient to enable them to react with any anti-ovalbumin in a serum. Twice recrystallized ovalbumin still contains some conalbumin. Sera raised against it may contain unexpectedly high levels of anti-conalbumin and this could cause confusion in tanned red cell tests. [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]

A number of fucose-containing glycolipids (fuco-lipids), which are similar in composition to those of human normal and malignant gastrointestinal tissue, have been isolated from whole small intestines of individual dogs. Dogs from which these fuco-lipids were isolated fell into two types according to the qualitative sugar composition of their fuco-lipids. Glycolipids from type I dogs contained glucose, galactose, glucosamine, galactosamine and fucose, while those from type II dogs contained the same sugars but lacked galactosamine. Fucolipids isolated from type I and II dogs were tested for both canine blood group and human A, B, H and Lea and Leb blood group activity. At the concentrations tested, only human blood group A activity was found in significant amounts, and only in those fucolipids which contained galactosamine (type I dogs). Of the fuco-lipids with human blood group A activity, some had activity comparable to that of glycoprotein blood group substances, while others had lower, but significant, activity. These latter fucolipids also had marked chromatographic differences, indicating that they are of several different structural types, a finding similar to the A active glycolipids of human red cell stroma. None of the isolated intestinal fuco-lipids had canine blood group activity. A fuco-lipid with Lea activity was also isolated in relatively large amounts from a normal human whole small intestine. [ABSTRACT FROM AUTHOR]

Experiments are described which show that effete red cells will not adhere to autochthonous macrophages which have been treated with trypsin. If, following trypsin treatment, the macrophages are incubated in the presence of normal guinea-pig serum, activity is restored and the adherence reaction with effete red cells can again be demonstrated. Activity is not restored by incubation with Hanks's solution following trypsin treatment. These results suggest that the adherence reaction is mediated by a component of normal guinea-pig serum which becomes adsorbed to the macrophage surface. Evidence is presented suggesting that the linkage between the serum component and the macrophage surface is protein in nature. The active component is removed from guinea-pig serum by absorption with effete red cells. [ABSTRACT FROM AUTHOR]

Fowls which tolerate foreign erythrocytes, but which have not received a transplant of variable cells, eventually lose tolerance when the supply of erythrocytes is discontinued. The loss follows, at an interval, after the foreign erythrocytes have been eliminated by the normal mechanism for removal of aged cells; earlier loss can be brought about by eliminating the foreign cells with passive antibody. The interval required for loss varies, for tolerance of homologous erythrocytes, from less than 5 to over 215 days. The age of the tolerance bird, and hence the duration of exposure to antigen, is the main factor influencing the interval required; the preceding level of tolerance exerts comparatively little effect. An attempt to terminate tolerance by adoptive immunization was only partially successful. [ABSTRACT FROM AUTHOR]

The kinetics of the reaction between C' I-esterase inhibitor and an intermediate complex of sensitized sheep erythrocytes and human complement are described. The rate of reaction was directly proportional to the concentrations of both inhibitor and intermediate complex, but was insensitive to changes in pH over the range 7.4 - 8.7 and in ionic strength from 0.15 - 0.24. The rate of reaction was accelerated b an increase in temperature over the range 22° - 37°. The experimental evidence was consistent with a mechanism picturing the reaction of C' I-esterase inhibitor with C' I-esterase bound to the intermediate complex. A theoretical treatment is described from which values for various kinetic and thermodynamic quantities may be calculated. [ABSTRACT FROM AUTHOR]

The value of sera containing immuno-conglutinin or conglutinin in demonstrating complement-binding by human blood group iso-antibodies was investigated. Provided that a suitable complement was used, positive results were obtained with all human sera which had been shown by other methods to contain complement-binding antibodies. When human red cells were sensitized with human complement-binding blood group antibody and then treated with horse serum as a source of complement, the strongest reactions were obtained with rabbit immuno-conglutinin; the reactions with bovine serum (containing conglutinin) were distinctly weaker, and the reactions with human sera containing immuno-conglutinin were weaker still. When rabbit complement was used instead of horse complement, stronger reactions were obtained, but it was difficult to avoid ‘false positive’ reactions. When human complement was used, good reactions were obtained with rabbit immuno-conglutinin, but the reactions with bovine conglutinin and human immuno-conglutinin were completely negative. [ABSTRACT FROM AUTHOR]

The injection of sheep red cells and capsular antigen of Pasteurella pestis leads to increase in the absolute and relative number of plasma cells in the draining lymph node and spleen. An equation is proposed which is compatible with the linear relationship which is observed between the logarithm of the antigen dose and the square root of the number of plasma cells. An index of homogeneity is derived from this equation which is related to the number of different antigenic determinants and different antigenic molecules in the immunogen. This index varied in the predicted way when mice were immunized with relatively pure and crude preparations of capsular antigen. [ABSTRACT FROM AUTHOR]

The effect of an horse anti-mouse thymocyte globulin (ALG) preparation on the primary and secondary immune responses to sheep erythrocytes (RBC) was studied in 2-3-month-old male A/HeJ, C57B1, BALB/c, DBA/1, CBA and C3H mice. A wide variation in the primary and secondary responses of the individual strains was noticed but in ail cases these were significantly suppressed by ALG pretreatment. The capacity of the ALG to suppress the primary immune response was not overcome by increasing the antigen dose from 3 × 107 to 3 × 109 sheep RBC. [ABSTRACT FROM AUTHOR]

Peritoneal exudate lymphocytes (PEL) of guinea-pigs injected with Freund's complete adjuvant (FCA) were capable of liberating skin reactive factor (SRF) and macrophage migration-inhibitory factor (MIF) when cultured for 24 hours in the presence of sheep red cells (SRC) preincubated with lymph node cells (LNC) of guinea-pigs immunized with SRC in FCA. Similar release of soluble mediators was found in the following situations: (a) incubation of non-immune PEL with SRC sensitized with the exclusion peak of Sephadex G-200 fractionated immune LNC supernatant; (b) incubation of non-immune LNC with complexes of SRC and anti-SRC IgG, prepared from serum of animals immunized with SRC in CFA, and (c) incubation of non-immune LNC with a mixture of SRc urea extract and anti-SRC IgG. SRC incubated for 24 hours with immune LNC and freed of lymphocytes by selective filtration through a Millipore filter, were able to provoke an inflammatory reaction in the skin of normal guinea-pigs, which was delayed in character. These findings are interpreted as suggestive evidence for the non-identity of the mediator-producing and antigen-reactive cells and as support for the hypothesis that a complex composed of antigen and an antibody-like material, secreted by stimulated antigen-reactive lymphocutes, is responsible for the release of soluble mediators in cell-mediated immune reactions. [ABSTRACT FROM AUTHOR]

Irradiated (NZB × BALB/c)F1 mice were injected with syngeneic bone marrow cells, syngeneic or parental thymus cells, and sheep red cells. The antibody plaque-forming cell response depended on the number of sheep cells and the age and strain of the thymus cells. Young or adult BALB/c thymus, and young hybrid thymus, responded best to low numbers of sheep cells; with higher numbers they became tolerant. Adult hybrid thymus, and young or adult NZB thymus, responded better to high numbers of sheep cells. Hybrid mice irradiated and restored with BALB/c bone marrow developed thymus cells with the reactivity of BALB/c thymus. It is argued that NZB mice, and older hybrids, may develop autoimmunity because of an abnormality of tolerance induction manifested in their thymus cells, but of bone marrow origin. [ABSTRACT FROM AUTHOR]

The red cell uptake of IgG on the basis of absorption experiments appears to be due to two populations of IgG molecules. One population is readily absorbable by red cells. The quantity of this type of IgG varies from preparation to preparation and appears to depend on the method used for preparing the IgG. It appears that this population of IgG molecules represents denatured or aggre- gated IgG, although no direct evidence of aggregation was obtained in these studies. The other population of red cell absorbable IgG appears to be proportional to the IgG concentration and cannot be depleted by successive red cell absorption of the IgG solution. A similar pattern of reactivity with red cells was found using [131I] IgM. Labelled subunits of IgM and fragments of IgG (Fab and Fc), differed from IgG and IgM in that they did not contain a population consisting of a variable quantity of readily absorbable molecules. [ABSTRACT FROM AUTHOR]

This article presents the study of canine erythrocyte antibodies. An adaptation of the Polybrene technique for typing of canine erythrocytes is reported in this paper. Dog whole blood was anticoagulated with acid-citrate-dextrose in a proportion of 1:9 The samples were stored at 40, and used within 10 days. Manual typing and titrations were performed. Adaptation of this technique to canine blood study required two modifications: 15 per cent bovine serum albumin was substituted for homologous normal serum; the concentration of Polybrene was reduced to 0.033 mg/ml. Results demonstrated that the Polybrene technique is from 12.5 (anti-A) to 3200-fold (anti-He) more sensitive than the manual technique.

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]

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]

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]

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]

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]

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]