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New short-lived strains of mice (SAM-P), which have been developed by Takeda et al. (1981), show a defective antibody response to T dependent (TD) antigen in vitro, as demonstrated in the accompanying paper (see page 419). In the present study, we investigated the cellular site of the defect, using a cell culture system. In this paper, it is demonstrated that T-helper (Th) cell activity for the antibody response to TD antigen is impaired, while other cellular immune responses, e.g. mixed leucocyte reaction, cytotoxic T-lymphocyte response, and delayed-type hypersensitivity reaction, are normal. These results suggest that the defect in T-helper subset is limited in helper function for the antibody response, and that the helper function for the cell-mediated immune responses is intact. These two functions of the T-helper subset are apparently regulated in a different manner. The SAM-P strains of mice may thus serve as an appropriate model for studying functional heterogeneity in T-helper/inducer cell subsets. [ABSTRACT FROM AUTHOR]

As described in an accompanying paper, trinitrophenyl (TNP) modification of pork insulin (PI) at the A1 glycine position allows this molecule to stimulate a proliferative response in H-2b (B10) mice. We now show that this antigen stimulates low IgG responses in the same strain of mice. Our results show that T-cell help and proliferation may therefore be regulated independently. [ABSTRACT FROM AUTHOR]

T-colony formation can be induced in PHA-stimulated peripheral blood mononuclear cells (PBM) from man, but not in PHA-stimulated purified T cells, the latter requiring the presence of factors produced by PHA-stimulated PBM and termed T-colony promoting activity (TCPA). In this paper, we demonstrate that interleukin-2 (IL-2), the growth hormone of T lymphocytes, controls T-colony formation. We show that: (i) IL-2 activity and TCPA produced by PHA-activated PBM are co-purified by gel filtration and chromatography on blue agarose, a procedure which yields a 850-fold IL-2 purification; (ii) recombinant IL-2, produced by genetically manipulated Eseherichia coli, can induce T-colony formation in PHA-stimulated purified T cells; (iii) Monoclonal antibody against the IL-2 receptor (anti-Tac antibody) completely inhibits the T-colony formation in PHA-stimulated PBM when directly added to the culture system. [ABSTRACT FROM AUTHOR]

The thoracic duct or efferent prescapular duct was cannulated in four fetal calves aged 121-259 days post-conception. The duration of lymph flow ranged from 2 to 20 days and the mean flow rates sustained over these collection periods varied from 54 to 488 ml/hr. Lymphocyte output ranged from 44 × 106 cells/hr in thoracic duct lymph from a 121-day fetus to 3.9 × 108 cells/hr in efferent prescapular lymph from a 259-day fetus. The circulating lymphocyte pool in fetal calves of about 120 and 190 days gestational age was calculated to contain, respectively, 4 × 108 cells and 2 × 1010 cells. The proportion of lymphocytes bearing surface immunoglobulin detected in fetal lymph ranged from 2.1% to 8.7%. Recirculating lymphocytes from fetal calves produced strong proliferative responses when stimulated by T-cell mitogens but responded poorly to B-cell mitogens. Fetal lymphocytes also responded to stimulation by allogeneic cells and stimulated other cells to proliferate during mixed lymphocyte culture. When stimulated with Con A, fetal lymphocytes secreted IL-2 to a degree that was indistinguishable from the secretory behaviour of lymphocytes from adult animals. The results presented in this paper show that chronic lymphatic fistulae can be established successfully in fetal calves to give access to recirculating lymphocytes. This provides a new experimental approach for studying the development of the bovine immune system. [ABSTRACT FROM AUTHOR]

In this paper we present experiments that indicate that, in man, most T-celI subpopulations produce interleukin-2 (IL-2), but that the main cell subpopulation which produces it, both upon activation with phytohaemagglutinin or in autologous mixed lymphocyte cultures, is that of autologous rosette-forming (Tar) T4+ T cells. Conversely, the main IL-2-responding T-cell subpopulation is that composed of T cells depleted of Tar (T-Tar) that are T8+ IL-2 was also found to be more effectively produced by Tar cells that do not bind peanut agglutinin (PNA) than by those that do. The PNA T4+ Tar cells were also found to respond best to interleukin- I (IL-I). [ABSTRACT FROM AUTHOR]

Sera from mice with large tumours from a variety of tissue types and sources have been shown to contain substances capable of suppressing the proliferative response of normal mouse lymphocytes to concanavalin A (Con A), bacterial endotoxin (LPS) and allogeneic cells. The present paper deals with studies on the nature of these inhibitory materials using mainly a methylcholanthreneinduced rhabdomyosarcoma in DBA/2J mice. It was found that a material responsible for inhibition of the Con A response eluted with immunoglobulins on Sephadex G-150 and eluted with monomeric immunoglobulin on Sephadex G-200. The component of tumour-bearer serum responsible for the suppression of the LPS response of normal lymphocytes eluted from Sephadex G-150 with the α and β globulins and albumin (molecular weight < 150,000). The immunoglobulin-containing serum fraction from tumour-bearing animals inhibited the mixed lymphocyte response, Con A response, and specific immune response to purified protein derivative (PPD) in allogeneic cell systems. It also inhibited the in vitro primary response of mouse cells to sheep red blood cells, and, to a lesser extent, the response to a T cell-independent antigen (DNP-dextran). The inhibitory activity continued to elute with monomeric IgG on Sephadex G-200 when columns were run in 1640 medium and adjusted to pH 2.5, indicating that an acid dissociable complex was not responsible for inhibitory activity. Inhibitor activity could be removed by absorption on immunoadsorbents containing goat anti-mouse immunoglobulin, and could be recovered by acid elution from the adsorbent. Inhibitor activity was not removed by immunoadsorption on columns prepared with antisera to chicken immunoglobulin. [ABSTRACT FROM AUTHOR]

A receptor which binds secretory lgA (sIgA) is expressed on human T cells from patients with systemic lupus erythematosus, rheumatoid arthritis, Behcet's syndrome and IgA nephropathy and on normal T cells following phytohaemagglutinin (PHA) stimulation. The specificity of this receptor was initially probed with a panel of normal serum immunoglobulins in competitive inhibition assays with sIgA using two-colour immunofluorescence. While the receptor showed the strongest affinity for igAl (IC5010-6 M), IgD which has a similarly glycosylated hinge region to IgAl, also bound to the receptor (IC50 10-5 M). IgA2, which lacks the 'O'-glycosylated hinge region, did not significantly inhibit the binding at these concentrations suggesting that the IgA determinants for this receptor might be the oligosaccharides present in the hinge region of IgAl. IgAl has up to 10 'O'-linked oligosaccharides and four N-linked oligosaccharides per molecule. In order to probe the role of the 'O'-linked hinge sugars in the binding event, a sugar library was prepared from IgAl by a procedure designed to release 'O'-linked oligosaccharides preferentially, and to retain them in the natural closed ring formation. The sugars were released by hydrazinolysis at 65° and the resulting oligosaccharide library analysed by high voltage paper electrophoresis (HVE) and P4 gel permeation chromatography. Competitive inhibition studies demonstrated that both the library and the individual 'O'-linked sugars associated with IgA1 were implicated in the binding of IgAl to this receptor (IC50 between 1 × 10-5 M and 6 × 10-s M). Within this range the individual sugars showed small differences in their affinity for the receptor in the following order: Galβ3GalNAc = NeuNAc2α3(6)Galβ3GalNAc > NeuNAc2α3(6)Galβ3[NeuNAc2α6]GalNAc ≥ GalNAc. [ABSTRACT FROM AUTHOR]

This paper describes a T-cell targeting strategy based on the use of an antigen-monoclonal antibody heteroconjugate. A rat anti-idiotypic monoclonal antibody specific for a murine B-cell lymphoma was conjugated to the purified protein derivative (PPD) of tuberculin. This construct selectively delivered up to 4.5 &times 104 molecules of PPD onto each tumour cell. Targeted PPD was internalized for endosomal processing and was presented in association with the I-A class II restriction element to PPD-reactive T-helper (Th) cells. Activated Th cells were demonstrated to proliferate and secrete significant levels of tumour necrosis factor (TNF). Such lymphokine secretion was observed at a PPD concentration as low as 1 ng/mI. Despite the secretion of TNF, the S-cell lymphoma was found to be resistant to autonomous Th-mediated cytotoxicity. Targeted Th cells did, however, activate tumourcidal macrophages that subsequently mediated significant tumour cytostasis. Based on this observation, it is proposed that the targeting system described may be exploited as the basis for a future immunotherapeutic strategy. [ABSTRACT FROM AUTHOR]

Lectins can be used to detect changes in cell-surface glycosylation. In this paper we examine the lectin-binding characteristics of murine T cells as measured by flow cytometry. A large panel of labelled lectins was used to stain naive, activated and resting murine T cells. Some lectins did not detectably bind any T cells, some bound to all T cells and some bound to only a subset of splenic T cells. Three lectins which preferentially bind to previously activated T cells were identified: Bandeiraea simplicifolia BS-I, Bauhinia purpurea and Lycopersicon esculentum. In addition, two lectins were found to bind preferentially to activated T cells; Glycine max and Triticum vulgaris. Finally, no differences were found in the ability of a large panel of lectins to bind to Th1 and Th2 clones. Lectin binding may be a powerful tool for distinguishing naive, activated and memory T cells. [ABSTRACT FROM AUTHOR]

Unfractionated and T-cell depleted human peripheral blood lymphocytes (PBL) were cultured in vitro in the presence of pokeweed mitogen (PWM) and Staphylococcus aureus strain Cowan I (StaCw). After 7 days of culture, the cells were assayed for cytoplasmic immunoglobulins (Cyto-Ig) by direct staining using fluorescein-labelled F(ab')2 fragments prepared from specific antisera against human IgG F(ab')2. The amount of immunoglobulin of the IgM and IgG class released into the cell-free supernatants was also measured by radioimmunoassay. In unfractionated PBL StaCw, like PWM, was able to induce a significant increase of either the number of Cyto-Ig containing cells or the amount of IgM And IgG secreted into the supernatant. In contrast, the amount of 1gM and IgG immunoglobulin released into the supernatant of T-cell depleted suspensions stimulated with PWM was significantly reduced in comparison with that of Unfractionated populations, whereas it was unchanged in T-cell depleted vs unfractionated suspensions stimulated with StaCw. The addition of a few I lymphocytes restored the ability of T-call depleted suspensions to produce Ig in the presence of PWM, whereas despite addition of high numbers of T cells no further augmentation of the Ig production induced by StaCw on T-cell depleted suspensions was observed. Cultures of umbilical cord blood lymphocytes (UCBL) stimulated with PWM did not generate Ig-producing cells, whereas UCBL stimulated with StaCw showed significant production of Ig of both 1gM and lgG classes. The results indicate that T lymphocytes are probably not involved either with stimulation or with the suppression of Ig production induced by StaCw. [ABSTRACT FROM AUTHOR]

Antibody production to influenza A strain virus X31 (H3N2) was measured in cultures of peripheral blood mononuclear cells (PBMC) stimulated with either antigen (X31) or pokeweed mitogen (PWM). With some donors, X31 antibody was produced in response to antigenic stimulation, but not as part of the polyclonal response to PWM, suggesting that antigen and PWM may be acting on different B-cell subpopulations. To test this hypothesis, T-cell depleted PBMC (E-) cells were fractionated on discontinuous Percoll gradients and assayed for antibody production in response to antigen or PWM. Fraction I (FrI = SC < 1.070) cultured in the presence of T cells responded well to PWM, but not at all to X31. FrII (1070 < SG < 1.075) and FrIII (SG > 1.075) cultured in the presence of T cells both responded well to X31, but only the medium-density B cells (FrII) were able to make specific antibody when T cells were replaced with T-cell replacing factor (TRF). Specific X31 antibody responses by medium- and high-density B cells (FrII and FrIII) were suppressed equally by the addition of allogeneic T-suppressor (Ts) cells. When allo-activated Ts cells were inactivated by irradiation, allogeneic T-helper (Th) cells were able to collaborate with both FrII and FrIII B cells in specific antibody responses to X31. Since TRF was not able to substitute for T cells in specific antibody responses by FrIII B cells, this result shows that allogeneic T-cell help was not mediated by non-specific 'allogeneic effect' factors and apparently requires cognate T cell-B cell interactions. [ABSTRACT FROM AUTHOR]

Anti-hepatitis B surface (HBs) antibodies have been induced in vitro by human peripheral blood mononuclear cells (PBMC) from individuals immunized with hepatitis S surface antigen (HBsAg). Anti-HBs antibody production is antigen-specific, T-cell dependent, class II MHC-restricted and requires de novo synthesis. Furthermore, HBsAg-specific CDB suppressor cells can also be induced in vitro after challenge with high antigen doses. Antigen presenting cells (APC) are required for the induction of suppression. These suppressor cells are antigen-specific since they do not suppress the antibody response to tetanus toxoid. Antigen-specific suppression is inhibited by cytotoxic treatment of CD8 CD11 cells with OKM1 monoclonal antibody (MoAb) and complement, suggesting that these suppressor CD8 cells may represent granular lymphocytes. Addition to cultures of high concentrations of a recombinant human IL-2 dose not affect suppression, ruling out the adsorption of IL-2 by suppressor cells as a possible mechanism for suppression. [ABSTRACT FROM AUTHOR]

Using a cell culture system, age-associated changes in immune activities were investigated in newly developed, short-lived mouse strains. These SAM-P strains of mice (H-2k), which have a remarkably short life span (around 9 months) under conventional breeding conditions, showed an age-associated early decline in several immune functions, as compared to ordinary strains of AKR/J (H-2k) and C3H/He (H-2k) mice. Their antibody-forming capacity to T-independent antigen, DNP-Ficoll, and natural killer (NK) cell activity showed a markedly early onset of regression and a sharp decline from the level of control mice at 2 months of age. SAM-P strains of mice have a profound defect in antibody response to a T-dependent (TD) antigen, such as sheep red blood cells (SRBC), thus there was only a feeble antibody response to SRBC as early as the age of 2 months, and a negligible response at a later age. In contrast, the allo-specific cytotoxic T lymphocyte (CTL) response of the mice was as high as that of control mouse strains at 2 months of age and declined little until at least 6 months of age. The early age-related functional decline in the immune system of SAM-P mice suggests that these new inbred strains are appropriate models for investigating the age-related appearance of immune dysfunctions. [ABSTRACT FROM AUTHOR]

The capacity of cloned murine Ia-positive BK-BI-2.6.C6 T cells to present protein antigens to antigen-reactive long-term cultured T-cell lines was investigated. Antigen recognition by T-line cells on presenting BK-BI-2.6.C6 T-accessory cells resulted in efficient production of lymphokines. While antigen-dependent T cells with transient interleukin-2 receptor (IL-2R) expression were not induced to proliferate, T cells with constitutive IL-2R expression proliferated in response to the secreted IL-2. Although antigen presentation by BK-BI-2.6.C6 T cells resulted in a slight induction of IL-2R expression on responding T cells, as measured by flow cytometry, this augmentation was much smaller than that induced by antigen-presenting spleen cells. Thus the inability of antigen-presenting T-accessory cells to stimulate proliferation of responding T cells with transient IL-2R expression appears to reflect a lack of signal(s) necessary for the induction of IL-2R up to a level critical for initiation of cell division. This test system represents an ideal model to investigate the nature of signals required, in addition to triggering of the T-cell antigen receptor, for the induction of IL-2R. [ABSTRACT FROM AUTHOR]

The distribution of the functional subsets of porcine T cells, the cytolytic/suppressor (Tc/s) and the helper/inducer (Th/i) cells was studied in cryostat sections of thymus, lymph nodes, tonsils, Peyer's patches, spleen and liver using the indirect immunoperoxidase technique. Three murine monoclonal antibodies (mAb) were used. The mAb 8/1 reacts with an antigen present on all T cells and on cells of the myeloid lineage; the antigen has not yet been characterized biochemically. The mAb 295/33 (anti- T8) binds to the porcine T8 antigen and defines the Tc/s subset, while mAb PT-4 (anti-T4) detects the porcine T4 antigen and defines the Th/i subset. Practically all thymocytes were stained by inAb 8/1. The majority of cortical thymocytes apparently co-expressed T8 and T4, whereas distinct fractions of medullary cells were labelled by either anti-T8 or anti-T4. In peripheral lymphoid organs all three mAb reacted with cells in the thymus-dependent areas and with cells scattered in the lymphoid follicles. In lymph nodes, tonsils and Peyer's patches, anti-T8 and anti-T4 each labelled approximately half of the cells stained by mAb 8/1. in the periarteriolar lymphoid sheath of the spleen, anti-T4 labelled more cells than did anti-T8. The reactivity of mAb 8/1 with the Kupffer cells of the liver demonstrated the expression of the 8/1 antigen on cells of the monocyte lineage. The T8 and T4 antigens could not be detected in acetone-fixed and paraffin-embedded sections, while the antigen recognized by mAb 8/1 remained preserved. Altogether, despite an inverted microanatomical structure of porcine lymph nodes, the frequency and distribution of T8+ and T4+ cells in thymus-dependent areas proved to be similar to those found in other species. [ABSTRACT FROM AUTHOR]

Low-density lymphocytes prepared by Percoll fractionation of human peripheral blood mononuclear leucocytes were found to produce large amounts of interferon-γ (IFN-γ) in response to different T-cell mitogens in the absence of macrophages, whilst higher density lymphocytes were strongly dependent on the presence of macrophages for significant IFN-γ production. The addition of macrophages to the low-density lymphocytes made little difference to their IFN-γ production. Subsets of the low- density lymphocytes prepared by rosetting with sheep red blood cells produced markedly less IFN-γ than did the original population; IFN-γ production could be largely restored by recombining the two low-density fractions. This suggests that IFN-γ production by low-density lymphocytes whilst macrophage-independent does require co-operation between different cell types. The low-density lymphocytes were enriched for cells bearing the Leu 11 and OKM1 antigens, and for natural killer cell activity. The rosetting fraction was enriched for OKT3 antigen-bearing cells, and the non-rosetting fraction was enriched for Leu 11, OKM1 antigen-bearing cells. Depletion of S cells (surface Ig- positive) by nylon-wool chromatography had no effect on IFN-γ production by low-density lymphocytes. [ABSTRACT FROM AUTHOR]

The induction of oral tolerance after ingestion of antigen has been reported in several animal models. The precise mechanisms responsible for this unresponsiveness are not well understood. As some investigations have suggested a key role of Peyer's patches suppressor T cells, an animal model was developed in which the PP were surgically removed. Using this model, the influence of the PP on the induction of oral tolerance against SRBC was investigated. In order to induce tolerance, the rats were fed SRBC on four consecutive days. On Day 5 they were i.p. challenged by injection of SRBC, and 5 days later the number of immunoglobulin-secreting cells against SRBC was determined within the spleen. Using this protocol, the oral tolerance induction could be shown very clearly in control animals as well as in rats without PP. Therefore, tolerance induction is possible in the absence of PP-T cells. Other mechanisms must be responsible for the tolerance induction in this model. [ABSTRACT FROM AUTHOR]

ST-1a and ST-1b, are monoclonal antibodies that selectively react with cells in the T-cell lineage of the sheep. Preliminary structural studies using radioimmunoprecipitation and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) indicated that both ST-1a and ST-1b recognize an antigen of apparent molecular weight 67,000 and 60,000-65,000, under either reducing or none reducing conditions. Differential expression of these 67,000 and 60,000-65,000 MW proteins was observed in T cells obtained from various anatomical compartments. Cortical thymocytes and efferent lymph lymphocytes expressed predominantly the 67,000 molecule, whereas a thymus cell fraction enriched for medullary thymocytes expressed mainly the 60,000-65,000 MW molecule. Both proteins were found in equivalent amounts in immunoprecipitates obtained from peripheral blood lymphocytes and lymph node lymphocytes. Peptide mapping studies indicated that 67,000 proteins of both ST-1a and ST-1b immunoprecipitates have significant homology in peptide composition. Sequential immunoprecipitation experiments clearly demonstrated that the antigens recognized by ST-1a and ST-1b antibodies are the same. On the basis of the size, tissue distribution and trypsin sensitivity of the antigen, together with cytofluorometry data, we suggest that the target antigen of ST-1a and ST-1b monoclonal antibodies is the ovine homologue of mouse Lyt-1 and human Leu-1. [ABSTRACT FROM AUTHOR]

Antigen-specific T-cell activation is mediated via the CD3-T1(antigen receptor) complex. and monoclonal antibodies to both CD3 and T1 cause a rapid rise in intracellular Ca2+. This calcium mobilization is not inhibited by monoclonal antibodies to CD2. The rise in calcium mobilization induced by purified PHA (PHA-P) does not occur in a cell line which lacks CD2 expression, and can be blocked in other I cells by anti-CD2 antibodies. A combination of monoclonal antibodies to different epitopes of CD2 causes calcium mobilization and mitogenesis. Reagent grade PHA (PHA- M) induces calcium moblization in cells that lack CD2, and its effects in other T cells cannot be blocked by anti-CD2 antibodies. The effects of PHA-P and PHA-M arc thus mediated predominantly through different activation pathways. [ABSTRACT FROM AUTHOR]

Two types of experiment using local labelling of lymph nodes with FITC showed that lymphocytes emigrate from lymph nodes, predominantly in blood in the pig and in efferent lymph in the sheep. In the first type of experiment with the pig, few ceils emigrated via the lymph, while the number of labelled cells in the blood increased progressively and the indices in mesenteric blood were always higher than in jugular blood in simultaneously-drawn samples. However, in the sheep, when efferent lymph flowed freely, very low numbers emerged in blood and continuing large numbers of lymphocytes emerged in efferent lymph. In the second type of experiment carried out wholely under anaesthetic on mesenteric lymph nodes in pigs and sheep, and on superficial inguinal lymph nodes in pigs, the lymph node was isolated, the lymph and venous drainage collected and only the arterial supply maintained. Large numbers of FITC+ lymphocytes emigrated via the vein in pigs with either node cannulation (i.e. up to 7% blood iymphocytes were labelled with an emigration rate of ∼108 cells/hr) but in sheep, while lymph contained ∼30-80% labelled cells and the emigration rate was also ∼108 cells/hr, the mesenteric blood contained very few labelled cells (∼0.2%, giving a mean venous emigration rate of 2.7 × 106/hr). Study of the type of lymphocytes emerging from labelled pig lymph nodes and spleen during the phase of major emigration showed that sIg+ B and E rosette-forming T cells, but almost no Null cells, are involved. [ABSTRACT FROM AUTHOR]

Both B lymphocytes and cytotoxic T lymphocytes respond to signals from the T helper (Th) compartment, and such signals are mediated by a number of biochemically distinct factors. This raises the question whether help for B cells and T cells is a function of one or several different kinds of Th cell. Here we describe an in vitro and in vivo study of this problem, using a Th clone, designated MTH-1. The clone carries the cell surface markers Thy-1 and L3T4a, but lacks Lyt-2. It recognizes a minor alloantigen shared by DBA/2, B10.D2 and NZB spleen cells, and such recognition is restricted by H-2Ed. Recognition of antigen in vitro is accompanied by secretion of IL-2. In vivo, both primary and secondary CTL responses to multiple minor alloantigens are enhanced by small numbers (≤104) of MTH-1 cells. Recognition of alloantigen in a T-depleted B cell population results in the polyclonal activation and maturation of the B cells to secrete immunoglobulin; also, antigen-primed B ceils are augmented in their in vivo synthesis of specific antibody to the Thy-1·1 alloantigen by around 105 MTH-1 cells. Taken together, these results suggest a single Th clone can help both B cells and T cells. [ABSTRACT FROM AUTHOR]

Lectin-free supernatants obtained from PWM-stimulated lymphocytes, enable B cells to proliferate and secrete immunoglobulin. Both functions arc augmented by the addition of irradiated T cells. In the presence of antigen, these supernatants also enhance specific anti-tetanus toxoid antibody production. The components of the supernatant responsible for these activities have a molecular weight between 30,000 and 60,000, and have the characteristics of non-specific factors: they are genetically unrestricted, and do not bind to either antigen or anti-DR affinity columns. There is no evidence that the partial T dependency of these factors is an indication that their target is a T cell. Instead, T cells appear necessary to move the B cell into a state of activation in which it becomes responsive to the factor. Alternative activation signals such as Staph. A. Cowan can substitute for T cell help in the proliferative response, but not for immunoglobulin or antibody synthesis. The implications of these results for the approaches used to detect and classify B cell growth factors are discussed. [ABSTRACT FROM AUTHOR]

Mechanisms by which T and B lymphocytes co-operate in the in vitro secondary antibody response to trinitrophenyl-conjugated soluble protein antigens were investigated. The generation of antibody responses was analyzed when haptenic and carrier determinants were either linked or non-linked. Ability to co-operate through each of these mechanisms was influenced by the experimental conditions employed, particularly the mode of preparation of the T cells and the antigen concentration used. Nylon wool filtration of T cells may deplete a T helper population involved in non-linked recognition interactions.

There is evidence that the T-cell antigen receptor is immunoglobulin-related and that normal human T cells express surface determinants which cross-react with chicken anti-F(ab')2, anti-α and anti-μ antibodies. Surface marker study of six neoplastic human T cell lines suggested that F(ab')2- and μ-cross-reactive determinants may be expressed independently of 2-cross-reactive determinants. F(ab')2-cross-reactive materials-F(ab')2-CRMs--were then isolated from several T-cell lines and analysed by reverse passive haemagglutination and in immunoprecipitation experiments by polyacrylamide disc gel electrophoresis in buffers containing sodium dodecyl sulphate (SDS-PAGE) under reducing conditions. It was shown that MOLT-4- and CCRF-CEM-derived F(ab')2-CRMs differ serologically and that α- are indeed expressed independently of F(ab')2- and μ-cross-reactive determinants. The F(ab')2-CRMs were shown to be T cell-derived, to express determinants similar to or identical with F(ab')2-cross-reactive determinants expressed in normal T-cell membranes and to correspond closely to T-cell antigen binding molecules. Evidence was also obtained that the two F(ab')2-CRMS differ from one another in molecular weight. SDS-PAGE under non-reducing conditions of MOLT-4- and CCRF-CEM-derived F(ab')2-CRMs identified major components of mol. wt. 135,000 and mol. wt. 330,000 respectively. Immunoprecipitation of 125I-labelled F(ab')2-CRMs by chicken anti-F(ab')2 followed by SDS-PAGE under reducing conditions identified major components of mol. wt. 80,000 and mol. wt. of 51,000 from CCRF-CEM-derived F(ab')2-CRMs and tentatively identified components of mol. wt. 52,000 and mol. wt. 23,000 from MOLT-4- derived F(ab')2-CRMs. [ABSTRACT FROM AUTHOR]

We have investigated the mechanism(s) by which mitogenic (concanavalin A [Con A], phytohaemagglutinin [PHA] and Lens culinaris agglutinin [LCA]) and non-mitogenic (soybean agglutinin, peanut agglutinin, wheat-germ agglutinin and poke-weed mitogen) lectins mediate, non-specifically, lectin-dependent lymphocytotoxicity (LDCC). We show that non-mitogenic lectins are ineffective mediators of LDCC, due to their inability to mediate effective binding of effector cytotoxic T cells (EC) and target cells (TC), and not to their failure to 'activate' TC-bound EC, as proposed before. Evidence is presented that in LDCC Con A and PHA exert their primary effect(s) by affecting the TC rather than the EC. Although the lectin LCA, unlike Con A and PHA, is equally reactive with either EC or TC, a direct comparison is difficult since the presence of LCA, but not Con A or PHA, during the entire assay is required for optimal kill. Furthermore, all three LDCC-supportive lectins (PHA, Con A and LCA) show a similar IC preference when tested in a EC-TC conjugation assay. Taken together, these results are inconsistent with the theory that lectins mediate LDCC by 'bridging' EC and TC through lectin-binding receptors followed by 'activation' of the TC-bound EC. We would like to suggest that the potential of mitogenic lectins to mediate EC-TC interaction is related to their modification of TC-surface constituents, possibly major histocompatibility complex determinants, rendering them recognizable, non-specifically by EC. [ABSTRACT FROM AUTHOR]

Different T-cell subsets participating in immune responses were detected at a high frequency by a modified virus plaque assay (VPA). By using the modified VPA, different activated T-cell subsets generated in primary immune responses, helper and suppressor T cells participating in antibody formation, and effector T cells involved in the delayed-type hypersensitivity (DTH) reaction were enumerated directly without in vitro antigen stimulation. The frequency of detection in immune systems used was 7·5–17·7 V-PFC/103 spleen cells. Although neither helper T cells for antibody formation nor effector T cells for DTH reaction were detected as V-PFC at a high frequency by the original VPA, it was also found in secondary immune response that Lyt 1 positive, antigen-specific helper and effector T-cell subsets, and cyclophosphamide (CY)-resistant precursors were enumerated at a high frequency by the modified VPA when they received in vitro antigen stimulation, and that the proliferative stage of these cells was critical for the development of V-PFC. [ABSTRACT FROM AUTHOR]

Small lymphocyte subsets were characterized radioautographically on the basis of several surface markers, viz. surface Ig (S-Ig), Thy-1 and Lyt (Ly-1, Ly-2 and 3) antigens in host lymphoid organs (thymus, spleen and blood) as well as at the turnout site at various stages of subcutaneous growth of two different syngeneic turnouts—MPC-11 plasmacytoma and WEH I- 164 fibrosarcoma in BA L B/c mice. In both tumour-host combinations there was a rise in the levels of null (S-Ig-, Thy-1-) small lymphocytes as well as the Ly-23+ subset of T small lymphocytes at all the sites examined. The absolute number of these two subsets also increased excepting the case of null cell rise in the thymus which was relative. The functional potentials of Lyt subsets were explored by employing in vitro and in vivo assays. While no appreciable levels of anti-turnout cytotoxic T cells (Tc) were detectable by a 51Crk release assay in the host spleen or the turnout-draining lymph nodes at any stage of growth of MPC-11 tumour, such Tc was generated in vitro by a co-cultivation of unprimed spleen cells with irradiated MPC-11 cells. These Tc were Thy-l+ and Ly-12+, as noted from antibody+C' mediated abrogation of cytotoxicity. These results suggested that the generation of anti-turnout Tc in vivo was suppressed in tumour-bearing hosts. The possibility of a cell-mediated suppression was tested by an adoptive transfer of thymocytes or splenocytes from turnout-bearing mice into naive or pre-immunized recipients which then received fresh turnout transplants. This procedure caused a specific enhancement of turnout growth in three tumour-host combinations: MPC-I 1 or WEHI-164 turnout in BALB/c mice and W-I fibrosarcoma in CBA mice. The suppressor lineage lymphocytes appearing in vivo were found to be Thy-1+ and Ly-1-, 2+, as noted from antibody +C' mediated abrogation of their turnout-growth promoting ability. They appeared earlier (7 days) in the thymus and later (> 2 weeks) in the spleen and then persisted during the turnout lifetime. The parallel kinetics of the increase in the overall level of Ly-23+ cells and the appearance of Ly-2(3)+ suppressor lineage T cells in tumour-bearing hosts may indicate that studies of T-cell surface markers may be useful in predicting changes in the functional lymphocyte subsets. [ABSTRACT FROM AUTHOR]

Inclusion of 14% Ficoll in the assay of rosette formation of human lymphocytes with mouse red blood cells (RBC) markedly enhances the cellular interaction. Both the strength of the rosettes (number of attached RBC) and the number of reacting lymphocytes are increased significantly, irrespective of the lymphocyte source—blood, lymph node and tonsil. In the presence of Ficoll, most of the sIg-bearing B lymphocytes [expressing receptors for Fc(IgG) and/or C3] and a significant number of the sheep RBC-rosetting T lymphocytes (particularly the nylon wool non-adherent subset from the tonsil), express receptors for the mouse erythrocyte. [ABSTRACT FROM AUTHOR]

Fluorescein conjugated Vicia villosa (Vv) lectin was used for direct staining of the surface of viable cells of various mouse lymphocyte populations. A varying proportion of polyclonally-activated T cells expressed Vv receptor although leas strongly than cells of an influenza virus-specific cytotoxic T lymphocyte (CTL) clone and blasts generated in the mixed lymphocyte reaction. Cyclosporin A (CyA) treatment markedly reduced the expression of Vv receptor following concanavalin A (Con A) stimulation by between 66% and 93% with a concurrent inhibition of blastogenesis and complete abrogation of cytolytic function. Resting mouse lymphocytes and B-cell blasts were always Vv-negative. However, non-specific suppressor factor producing non-cytotoxic T-cell lines also expressed Vv receptor as shown by the weak, but specific, surface fluorescence of EL4 and BW5147 cells stained with Vv. Vv-positive cells were not restricted to a particular Ly phenotype, Vv-positive cells being found among both Lyt 1+ and Lyt 2+ MLC stimulated lymphocytes. Our data suggest that the receptor for Vv lectin cannot be regarded as an exclusive differential marker for CTL. [ABSTRACT FROM AUTHOR]

The supernatant of 'crowded' but not 'spread' rabbit spleen cell cultures contains a macroglobulin factor which behaves in an Ig-turnover assay as any T-independent antigen or polyclonal B-cell activator (PBA). In the supernatants of crowded rabbit lymphoid cell cultures prepared in serum free medium, the factor was found to be associated entirely with the α-macroglobulin (αM) fraction (α1 + α2). This αM was most probably actively secreted by the lymphocytes because: (i) sequential supernatants obtained in serum free medium of crowded cultures contained equal amounts of αM as well as equal PSA activity; (ii) the αM became labelled when the cells were grown in medium containing a radioactive amino acid. Macrophages were not required for the production of PBA. PBA was not produced when either crowded B or T cells were cultured alone but only when they were cultured together. Purified T cells were not triggered by any plant lectin to produce PBA. By use of anti-α2M allotype antibodies and B and T cells from different rabbits, the PBA was shown to have the allotype of the T-cell donor. The PSA was associated with rabbit α2M but not α1M. We concluded that upon close contact, B cells stimulate T cells to produce a PBA associated with α2M. [ABSTRACT FROM AUTHOR]

The localisation of subpopulations of T lymphocytes as defined by the monoclonal antibodies W3/25 and MRC OX 8 was determined by an indirect immunoperoxidase technique on cryostat sections of rat lymphoid tissues. Both subpopulations were present throughout T-dependent areas with only scattered T cells, largely W3/25 positive, in the B areas. The W3/25 antigen was also found on macrophages in the medulla of lymph nodes and in the peritoneal cavity and liver. [ABSTRACT FROM AUTHOR]

New Zealand White rabbits were killed 7 days after immunization with 1 mg of alum precipitated, keyhole limpet hemocyanin (KLH) into each hind footpad and 3 days after intraperitoneal injection of thioglycollate. When supernatants from cultures of purified, elicited macrophages were added to Mishell-Dutton cultures of primed popliteal lymphocytes, they induced synthesis of both general immunoglobulins and antibody specific for KLH. The active factor(s), polyclonal lymphocyte activator (PLA), appears to be a glycoprotein with a molecular weight between 150,000 and 200,000 daltons. Absorption with high concentrations of thymocytes but not bone marrow cells removed polyclonal stimulatory activity from peritoneal macrophage supernatants which contained PLA. Purified lymph-node B cells were sitmulated by PLA only in the presence of T cells. In addition, supernatants from PLA activated, washed T cells were effective at inducing polyclonal B-cell activation. Thus, PLA appears to act indirectly on B cells by stimulating T cells to produce a soluble factor which induces polyclonal B-cell activation. [ABSTRACT FROM AUTHOR]

Rat monoclonal antibody M1/69.16 reacts with a heat stable antigen of mouse commonly expressed in the majority of cell types in blood, spleen, bone marrow and thymus, including cells of erythroid, myeloid and lymphoid series. However, subpopulations of cells in lymphoid tissues can be identified which are non-reactive with this antibody using the fluorescence-activated cell sorter. All surface Ig positive cells seem to react with M1/69.16 while more than 96% of Ig negative cells in spleen and lymph nodes are M1/69.16 negative. Most ceils (80%–90%) in the M1/69.16 negative populations in spleen lymph nodes and bone marrow express Thy-1. Thus, peripheral T cells are specifically non-reactive with this antibody, In contrast, approximately 95% of thymocytes react with M1/69.16, leaving a minor population which is negative. The negative population (5%) is enriched in cells expressing high amounts of H-2 antigen and those bearing H9/25 antigen which is specific for lymphocyte subsets, indicating that M1/69.16 negative thymocytes represent a specific subpopulation, possibly ‘mature’ thymocytes. [ABSTRACT FROM AUTHOR]

The complement-mediated lysis of human lymphocytes by three monoclonal anti-human T-cell antibodies OKT3.PAN, OKT4.IND and OKT8.SUP was studied. The percentages of Ficoll-Hypaque-isolated mononuclear cells lysed by these antibodies were respectively: 65% for OKT3.PAN, 39% for OKT4.IND and 20% for OKT8.SUP. Optimal lymphocytotoxic reactions were noticed when unabsorbed rabbit serum was used as the source of complement (C). Addition of heat-inactivated human, mouse and newborn calf sera but not of foetal calf serum inhibited the lyric activity of the antibodies. Treatment of peri- pheral mononuclear blood cells with OKT3.PAN and C abrogated their mitotic response to PHA and Con-A. Sheep erythrocyte rosetting lymphocytes (E+ cells) treated with OKT4.IND or OKT8.SUP and C exhibited no marked changes in responsiveness to PHA, Con-A or allogeneic non-T cells.However, only E+ cells enriched with OKT4.IND-reactive cells responded to purified protein derivative, proliferated in the autologous mixed lymphocyte reaction and were highly sensitive to hydrocortisone suppression when stimulated by PHA. Our data indicate that these monoclonal antibodies can be regarded as invaluable tools for enumeration, characterization and functional assessment of human T cells and their subclasses. [ABSTRACT FROM AUTHOR]

Immune responses against bovine serum albumin by chickens were dependent upon thymusderived cells. Thirty-five of seventy chickens that had been neonatally thymectomized and subsequently immunized with bovine serum albumin produced lgM antibodies, but not IgG antibodies, against the antigen. T cells (IgM-T cells) of such chickens were able to help B cells to produce IgM antibody responses but were not able to help them to switch IgM- to IgG-antibody responses. Helper activity of the IgM-T cells was much less susceptible to the cytotoxic effect of anti-thymus cell serum and complement than was that of normal T cells. The introduction of the IgM-T cells into normal chickens at the same time as the initiation of immunization of the chickens did not affect immune responses by them at all, indicating the absence of suppressor T cells in the IgM-T cell preparations. Injection of chicken thymus factor into immunodeficient chickens transplanted with normal B cells and IgM-T cells developed the capability to help B cells to switch IgM- to IgG-antibody responses. On the basis of these findings the authors propose the existence of helper T cells which are characterized by peripheralization in early periods of ontogeny, the possession of helper activity for only IgM-antibody responses, the lack of helper activity for the switch from IgM- to IgG-antibody responses and relative insusceptibility to the cytotoxic effect of anti-thymus cell serum and complement. [ABSTRACT FROM AUTHOR]

The capability of Lens culinaris agglutinin (LcA) to induce selectively the helper T cell activity affecting primary antibody response was demonstrated. In the presence of mouse spleen cells, activated with LcA at a concentration of 12.5 µg/ml, optimal augumentation of the humoral immune response to sheep erythrocytes (SRBC) was observed. It was also demonstrated that Limulus polyphemus agglutinin (LPA), which was shown to possess carbohydratebinding specificity directed to sialic acid residues, preferentially agglutinated helper T cells. Conversely, peanut agglutinin (PNA), which binds preferentially to the sugar sequence β-D-Gal-(1→3)-D-GalNAc, did not agglutinate the helper cells. Furthermore, the stimulatory effect of LPA-agglutinated cells on the antibody response was abolished by treatment of the cells with anti-Thy-1.2 and complement. These results suggested that the helper cells induced by LcA were T cells and that they have abundant sialic acid residues exposed on the cell surface. [ABSTRACT FROM AUTHOR]

Thy-1 antigen and GPCA-the mouse T-cell surface component responsible for activation of guinea-pig complement (C)-were readily demonstrated on unstimulated but not on Con A-stimulated thymus or spleen cells when (guinea-pig) C-dependent cytotoxic reactions were used. Mitogenic stimulation was a necessary condition for these changes to occur since mere incubation of thymocytes in the absence of Con A failed to alter the sensitivity of these cells to treatment with either anti-Thy-l.2 antibodies plus C (devoid of non-specific cytotoxicity) or untreated guinea-pig serum (GPS) alone. Both Thy-l.2 and GPCA were, however, readily detectable on the Con A blasts when tested for by indirect immunofluorescence and immune adherence, respectively, i.e. by using tests which do not involve C-effected lysis. That Thy-1 was indeed expressed on the T-cell blasts was further indicared by their capacity to absorb anti-Thy-l.2 activity from specific antiserum. Con A, whether bound to the cells or added in excess to the reaction mixture, did not interfere with C-mediated lysis and was ruled out as a possible C inactivator. Pre-treatment of the lymphoblasts with neuraminidase rendered these cells sensitive to lysis by either anti-Thy-l.2 plus C or GPS. These results, highlighting altered reactivity of mouse T lymphoblasts with guinea-pig C, indicated the occurrence of surface changes during mitogen-induced blastogenesis and suggested a role for sialic acid residues in interference with C-dependent cylotoxicity. [ABSTRACT FROM AUTHOR]

A soluble factor(s), human T-lymphocyte derived help factor (HHF), generated following pokeweed mitogen (PWM) activation of irradiated human peripheral blood T lymphocytes was shown to substitute partially for T-lymphocyte helper activity in the T-lymphocyte dependent PWM- stimulated synthesis of immunoglobulin by B cells. The degree of help provided was proportional to the number of cultured irradiated T-lymphocytes producing factor as well as the amount of factor added to the B-cell culture. The helper effect was equally provided by HHF syngeneic and allogeneic to the B lymphocyte. Although there was little stimulation of total protein synthesis, the synthesis and secretion of IgG, IgM and IgA were all stimulated three- to ten-fold by this factor. The B cells required a minimum of 40-55 h exposure to the factor from the initiation of the culture for an increase in Ig synthesis on day 5 to be observed. Addition of HHF to B cells pre-incubated with PWM for different time intervals showed that a maximum helper effect was exerted when the factor was added on day 0. Addition on day 1 provided less than 20% of maximum help. The factor did not promote significant increases in either B-cell or T-cell cell division. [ABSTRACT FROM AUTHOR]

Antigen-antibody complexes efficiently inhibit the induction of antibody formation. Using Mishell-Dutton cultures, it can be demonstrated that neither T cells nor their products are required for this inhibition of IgM PFC formation. The blockade is at the level of B cells and cannot be overcome by LPS or TRF. The data demonstrate that cross-linking of antigen- and Fc-receptors by antigen-antibody complexes is a blocking signal for B cells. [ABSTRACT FROM AUTHOR]

Cultured female spleen cells develop less cytotoxicity to embryo-associated antigens than do cultured male spleen cells. This difference is less pronounced if the cells are treated before culture with a specific hetero-anti-B cell antiserum. Female non-T cells (especially from primiparous animals) can decrease the spontaneously developing T-cell cytotoxicity in male splenic T lymphocytes upon culture. By artificially manipulating the T cell: non-T cell ratio in the spleen population prior to culture, it seems one can alter the type of cytotoxic mechanism (to embryo-associated antigens) which develops in the cultures. [ABSTRACT FROM AUTHOR]

Normal thymus lymphocytes and T cells of mice have the ability to bind heat-aggregated IgG of human origin (aggHIgG), as shown by indirect immunofluorescence. At 4°, the cells hind aggHIgG with an irregular speckled appearance; at 37°, the aggregates are incorporated into the surface membrane, inducing rearrangement of tile receptors and capping. At the point of maximum binding capacity, thymocytes show a fairly homogeneous fluorescence pattern, whereas T cells show a heterogeneous appearance. Aggregated pure human Fc fragments, but not Fab fragments, retained not only the binding capacity of the complete molecule but also the ability to induce cap formation on the surface of thymus cells, at 37°, [ABSTRACT FROM AUTHOR]

Receptors for the Fc region of immunoglobulin 0 (IgU) (FcγRs) exist in three main forms: membrane bound, soluble and cytoplasmic. The function of cytoplasmic FcγRs is poorly understood, We have previously demonstrated cytoplasmic FcγRII (cCD32) within most normal human peripheral blood lymphocytes (PBL), including I cells. In this study we have investigated the hypothesis that following lymphocyte activation, up-regulation of cCD32 occurs, resulting in increased expression at the cell surface. Normal PBL were activated in vitro using a two-way mixed lymphocyte reaction (MLR) and expression of CD32 monitored by flow cytometry and by immunoperoxidase staining using specific monoclonal antibodies and aggregated mouse IgG sub- classes. Furthermore, we designed oligonucleotide probes specific for the three main isoforms of CD32 and looked for changes in mRNA expression throughout the MLR using an in situ hybridization technique. Increased surface expression of CD32 was found on both activated human T and B lymphocytes, but this was found only in the early stages of the MLR, on days 3 and 4, and was virtually absent by day 7. An inverse relationship between cell surface expression of CD32 and mRNA for the IIb isoforms was noted with strong mRNA expression for lib isoforms occurring in the later stages of the MLR (days 6-7) when interleukin-2R (IL-2R)- positive I cells were predominant. A soluble IgG binding factor (soluble CD32?) was also detected in the MLR culture supernatant. These observations provide support for the hypothesis that synthesis of Jib isoforms of CD32 occurs following alloantigen activation of human T lymphocytes. [ABSTRACT FROM AUTHOR]

The CTLL-2 bioassay is used frequently to determine interleukin-2 (IL-2) concentrations in experimental samples, including samples that contain reagents which affect the CD28-B7 interaction. We therefore evaluated whether the CD28-B7 pathway plays a role in the growth of CTLL-2 cells. Flow cytometry demonstrated that CTLL-2 cells express both CD28 and B7-1. CTLA4-immunoglobulin (CTLA4-Ig) inhibited the growth of CTLL-2 cells over a range of IL-2 concentrations, suggesting that the CD28-B7 interaction plays an important role in the growth of CTLL-2 cells. Anti-B7-1 antibody also inhibited CTLL-2 proliferation at all concentrations of IL-2. These results indicate that the CTLL-2 bioassay may not be a reliable means of determining IL-2 levels in experimental samples containing reagents that affect the CD28-B7 interaction. They also suggest that co-expression of CD28 and B7 may contribute to the growth of malignant T cells. [ABSTRACT FROM AUTHOR]

Because the T-cell receptor (TCR) α-chain locus is known to lack allelic exclusion of rearrangements, and as a recent report revealed the existence of α-chain double expressers among normal human peripheral blood lymphocytes (PBL), the possible existence of TCR α-chain double expressers among mature routine T cells was examined. Although two-colour staining analysis of normal T-cell populations did not immediately reveal recognizable clusters of Vet double expressers, alternative/n vitro stimulations of normal murine T cells with antibodies to two different TCR Vα chains reproducibly induced TCR α-chain double-expresser lines. TCR complexes with different α-chains on such T cells were both shown to be functional. The cell lines were heterogeneous with respect to Vβ usage and the ratio of the expressed amounts of the two α-chains on the surface. The ratio of the two expressed α-chains was found to be very stable over a long period of time. These results are consistent with the earlier report on α-chain double expressers among human T cells and also show normal occurrence of TCR α-chain double expressers in routine T-cell populations. [ABSTRACT FROM AUTHOR]

In this study, we examined the ability of varying populations of donor cells from B6 mice to induce hyporesponsiveness in T lymphocytes from C3H mice in vitro and in vivo. Small, resting B lymphocytes were inefficient stimulators of T-lymphocyte proliferation compared to splenic mononuclear cells (SMNC) and lipopolysaccharide (LPS)-induced B-cell blasts in vitro (P < 0.05). Pretreatment of SMNC with anti-B7-1 or anti-intracellular adhesion molecule-1 (ICAM-1) monoclonal antibodies (mAb) similarly resulted in inefficient stimulation of T-cell proliferation in vitro (P < 0.05). However, in vivo, only intrahepatic, but not intravenous, injection of donor cells into C3H mice resulted in decreased T-lymphocyte proliferation in response to restimulation by alloantigen. This effect was most pronounced following intrahepatic injection of resting B lymphocytes or SMNC pretreated with anti-ICAM-1 mAb compared to uninjected or intravenously injected mice (P < 0.05). The hyporesponsiveness was associated with an increased production of interleukin-4 (IL-4) by the responder T lymphocytes and correlated with enhanced skin allograft survival. These data demonstrate that intrahepatic injection of donor-derived cells induces T-lymphocyte hyporesponsiveness. The mechanism appears to be modulated by an ICAM-1-mediated signal resulting in expansion of an IL-4-producing T-lymphocyte population. [ABSTRACT FROM AUTHOR]

Ricin has been shown to enhance IgE production in the rat, probably through inhibition of suppressor T lymphocytes. We have studied further the effects of tic-in on IgE titre and have determined its effects on antigen-induced airway inflammation and hyperreactivity in the Brown Norway rat. Immunization with ovalbumin (l-100 μg, intraperitoneally) produced dose-related increases in serum antigen-specific IgE titre. Ricin augrnented the total IgE titre and caused about a 10-fold increase in the peak antigen-specific IgE titre. In sensitized animals, antigen challenge (three times with aerosolized ovalbumin every second day) caused a significant influx of eosinophils and neutrophils and significant airway hyperreactivity 24 hr after the third challenge. In sensitized animals that had also received ricin, the eosinophil and neutrophil influx was further significantly potentiated and a significant influx of lymphocytes also occurred. Thus, there was a relationship between the degree of sensitization and the magnitude of the inflammatory response. However, the enhanced airway inflammation in ricin-treated animals was not accompanied by a further enhancement of airway hyperreactivity. The present study demonstrates that ricin enhances IgE production and augments an antigen-induced inflammatory pathology but does not potentiate antigen-induced airway hyperreactivity. [ABSTRACT FROM AUTHOR]

Severe combined immunodeficient (SCID) mice, lacking mature T and B cells and virtually devoid of endogenous serum immunoglobulins, spontaneously produce large amounts of human immunoglobulin after transplantation with human peripheral blood lymphocytes (PBL). Moreover, after immunization with antigen an active immune response resulting in a production of specific antibodies can be induced. Here we report that human T cells must be co-transplanted with B cells into the SCID mice for immunoglobulin production to occur. Resting human B cells could be activated to immunoglobulin production in the absence of human monocytes and a specific antibody response to tetanus toxoid (TT) could be induced, suggesting that the human B cells could present antigen to T cells in the SCID environment. Production of human immunoglobulins, as well as specific antibodies, was obtained only if CD4+ T cells of the memory phenotype, i.e. expressing CD45RO, were present. No human immunoglobulin, either of IgM or of IgG isotype, was found in SCID sera if mice were co-transplanted with human B cells and CD45RA expressing CD4+ T cells. However, FACS analysis revealed that the transplanted CD45RA+ cells became activated and differentiated towards CD45RO+ cells within 1-2 weeks. These cells also gained the lymphokine gene expression pattern associated with CD45RO+ cells, as demonstrated by polymerase chain reaction (PCR) analysis, and could support immunoglobulin production in SCID mice transplanted with fresh B cells. In fact, after differentiation of CD4+ CD45RA+ T cells towards expression of CD45RO, either in vivo in the SCID mouse or in vitro, these cells could interact with and activate human B cells to immunoglobulin production. [ABSTRACT FROM AUTHOR]

In this study the involvement of peripheral γδ T cells, prepared by flow cytometry, in the immune response of cattle to primary infection with Trypanosoma congolense was assessed. Negligible in vitro proliferative responses were observed in γδ T cells isolated from trypanosusceptible Boran (Bos indicus) cattle at all stages examined post-infection when stimulated in vitro with parasite antigens. In contrast, both CD8+ T cells and γδ T cells from trypanotolerant N'Dama (Bos taurus) cattle proliferated markedly when stimulated in vitro with a complex of invariant trypanosome antigens with MW between 100 000 and 140 000 (100 000 MW complex). Neither species of cattle exhibited significant T-cell recognition of trypanosome variable surface glycoprotein (VSG). To study further the functional and phenotypic characteristics of the γδ T-cell response, four T-cell lines were established from infected N'Dama cattle. These cell lines were comprised of up to 96% γδ (WC1+) T cells, the remainder being CD8+ T cells. Two of these γδ T-cell lines exhibited 100 000 MW complex antigen specificity which was not major histocompatibility complex (MHC) restricted in one line. [ABSTRACT FROM AUTHOR]

Examines the effects of monoclonal antibodies to rat adhesion/accessory molecules on the binding of normal and concanavalin A-activated rat spleen lymphocytes to cultured unstimulated and interferon-gamma-stimulated endothelium and pigment epithelium. Data demonstrating that the system is important in lymphocyte trafficking into the eye only after lymphocyte activation.

For the inhibition of T-lymphocyte proliferation in mixed lymphocyte culture (MLC) by in vivo alloantigen-induced specific T-suppressor cells (Ts), the Ts and responder cells must have major histocompatibility complex (MHC) class II identity, either in I-C or in I-A+I-E. In the case of I-C, the molecule is on the surface of the Ts and not on the surface of the stimulator or responder cells. This lack of I-C on the responder cells occurs even after pre-activation by antigen. l-J on the Ts is unimportant in the present system, by blocking the Ts surface molecules with antibody, it was shown that the two Ts genetic restrictions were due to distinct Is subsets, hearing I-C in one case and I-A + I-E in the other. Pretreatment of the Ts with anti-I-C antibodies(without complement) did not prevent specific Is binding to the alloantigen, as shown by absorption on monolayers. However, it blocked the ability of the Ts to cause suppression and this could be reversed by removal of the antibody with pronase. The responder population, when pre-activated. could be fractionated by absorbing on monolayers of syngeneic Ts. Under these conditions, the cells sensitive to suppression adhered to the monolayer. while the non-adherent cell could not he suppressed. It is proposed that a receptor, to an Ia molecule (I-C or I-A + I-E) of the Ts, appears on the surface of the pre-activated responder T cell and that this is required for the genetically restricted interaction between the responder cell and the [ABSTRACT FROM AUTHOR]