Proliferation of B and T cells in mixed lymphocyte cultures

Nrf2-dependent and -independent effects of tBHQ in activated murine B cells

Nrf2 is a transcription factor that regulates cytoprotective cellular responses to oxidative and electrophilic stress. Nrf2 is potently activated by the synthetic food additive, tert-butylhydroquinone (tBHQ), which is widely used as a preservative in oils and processed foods. Previously published studies have established that tBHQ has numerous effects on T cell function. The purpose of this study was to determine the effect of tBHQ on B cell function and the role of Nrf2 in these effects. Specifically, we investigated T cell-independent B cell activation, differentiation, and IgM antibody production. Murine wild-type and Nrf2-null splenocytes were isolated, treated with tBHQ (0.25-2.5 μm), and activated by lipopolysaccharide (LPS), a T cell-independent B cell activator. Our findings indicate that tBHQ significantly enhanced IgM production in activated wild-type, but not Nrf2-null, B cells, suggesting this effect is Nrf2-dependent. In contrast, tBHQ significantly decreased the induction of CD69, CD25, CD22, and CD138 in both wild-type and Nrf2-null splenocytes. These findings indicate that the tBHQ-mediated increase in IgM is Nrf2-dependent, whereas the inhibition of CD69, CD25, CD22 and CD138 is Nrf2-independent. Overall, this study demonstrates that in addition to its effects on T cells, tBHQ also has potent effects on T cell-independent B cell function.

Changes in Reactivity In Vitro of CD4+CD25+ and CD4+CD25- T Cell Subsets in Transplant Tolerance

Transplant tolerance induced in adult animals is mediated by alloantigen-specific CD4⁺CD25⁺ T cells, yet in many models, proliferation of CD4⁺ T cells from hosts tolerant to specific-alloantigen in vitro is not impaired. To identify changes that may diagnose tolerance, changes in the patterns of proliferation of CD4⁺, CD4⁺CD25⁺, and CD4⁺CD25⁻ T cells from DA rats tolerant to Piebald Virol Glaxo rat strain (PVG) cardiac allografts and from naïve DA rats were examined. Proliferation of CD4⁺ T cells from both naïve and tolerant hosts was similar to both PVG and Lewis stimulator cells. In mixed lymphocyte culture to PVG, proliferation of naïve CD4⁺CD25⁻ T cells was greater than naïve CD4⁺ T cells. In contrast, proliferation of CD4⁺CD25⁻ T cells from tolerant hosts to specific-donor PVG was not greater than CD4⁺ T cells, whereas their response to Lewis and self-DA was greater than CD4⁺ T cells. Paradoxically, CD4⁺CD25⁺ T cells from tolerant hosts did not proliferate to PVG, but did to Lewis, whereas naïve CD4⁺CD25⁺ T cells proliferate to both PVG and Lewis but not to self-DA. CD4⁺CD25⁺ T cells from tolerant, but not naïve hosts, expressed receptors for interferon (IFN)-γ and IL-5 and these cytokines promoted their proliferation to specific-alloantigen PVG but not to Lewis or self-DA. We identified several differences in the patterns of proliferation to specific-donor alloantigen between cells from tolerant and naïve hosts. Most relevant is that CD4⁺CD25⁺ T cells from tolerant hosts failed to proliferate or suppress to specific donor in the absence of either IFN-γ or IL-5. The proliferation to third-party and self of each cell population from tolerant and naïve hosts was similar and not affected by IFN-γ or IL-5. Our findings suggest CD4⁺CD25⁺ T cells that mediate transplant tolerance depend on IFN−γ or IL-5 from alloactivated Th1 and Th2 cells.

TaqMan real time RT-PCR assays for detecting ferret innate and adaptive immune responses

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The ferret model is used to study human disease and physiology.

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TaqMan realtime RT-PCR assays for ferret cytokine and chemokine mRNA were developed.

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Cytokine and chemokine patterns in ferret cells were similar to other mammals.

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A comprehensive panel of mRNAs can be measured in samples of limited quantity.

The ferret is an excellent model for many human infectious diseases including influenza, SARS-CoV, henipavirus and pneumococcal infections. The ferret is also used to study cystic fibrosis and various cancers, as well as reproductive biology and physiology. However, the range of reagents available to measure the ferret immune response is very limited. To address this deficiency, high-throughput real time RT-PCR TaqMan assays were developed to measure the expression of fifteen immune mediators associated with the innate and adaptive immune responses (IFNα, IFNβ, IFNγ, IL1α, IL1β, IL2, IL4, IL6, IL8, IL10, IL12p40, IL17, Granzyme A, MCP1, TNFα), as well as four endogenous housekeeping genes (ATF4, HPRT, GAPDH, L32). These assays have been optimized to maximize reaction efficiency, reduce the amount of sample required (down to 1 ng RNA per real time RT-PCR reaction) and to select the most appropriate housekeeping genes. Using these assays, the expression of each of the tested genes could be detected in ferret lymph node cells stimulated with mitogens or infected with influenza virus in vitro. These new tools will allow a more comprehensive analysis of the ferret immune responses following infection or in other disease states.

Regulation of B-cell responses by Toll-like receptors

The discovery of host-encoded gene products that sense molecular patterns in infectious microbes, and the demonstration of their role in triggering innate and adaptive immune responses, has been a key milestone in our understanding of immunology. Twenty-three years after Janeway first outlined the fundamental concepts of the 'pattern recognition' model, and 15 years since the identification of Toll-like receptors (TLRs) as pattern recognition receptors (PRRs), new insights continue to be revealed, and questions remain. For example, innate immune responses to microbes that are mediated by PRRs have historically been viewed as the domain of innate immune cell populations such as dendritic cells and macrophages. New evidence, however, has pointed to the role of B-cell-intrinsic TLR activation in shaping antibody responses. These studies have revealed that TLRs regulate a complex transcriptional network that controls multiple steps in the development of antigen-specific antibodies. This review covers these recent developments regarding the role of TLRs in B-cell gene expression and function in vitro and in vivo, and highlights the remaining challenges in the field, with particular emphasis on the role of TLRs in antibody responses to viral infection. A more complete understanding of how TLRs regulate antibody responses will lead to improved vaccine design.

Therapy of B-cell malignancies by anti-HLA-DR humanized monoclonal antibody, IMMU-114, is mediated through hyperactivation of ERK and JNK MAP kinase signaling pathways

A humanized IgG4 anti-HLA-DR monoclonal antibody (IMMU-114), engineered to avoid side effects associated with complement activation, was examined for binding and cytotoxicity on leukemia, lymphoma, and multiple myeloma cell lines and chronic lymphocytic leukemia (CLL) patient specimens, followed by evaluation of the effects of IMMU-114 on extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways. HLA-DR was expressed on the majority of these cells at markedly higher levels than CD20, CD22, and CD74. IMMU-114 was toxic to mantle cell lymphoma, CLL, acute lymphoblastic leukemia, hairy cell leukemia, non-Hodgkin lymphoma (including rituximab-resistant), and multiple myeloma cell lines, and also patient CLL cells. IMMU-114 induced disease-free survival in tumor-bearing SCID mice with early-stage disease and in models that are relatively resistant to anti-CD20 monoclonal antibodies. Despite positive staining, acute myelogenous leukemic cells were not killed by IMMU-114. The ability of IMMU-114 to induce activation of ERK and JNK signaling correlated with cytotoxicity and differentiates the mechanism of action of IMMU-114 from monoclonal antibodies against CD20 and CD74. Thus, antigen expression is not sufficient for cytotoxicity; antibody-induced hyperactivation of ERK and JNK mitogen activated protein kinase signaling pathways are also required.

In vivo responses of alloreactive lymphocytes stimulated in vitro. Skin graft rejection mediated by MLR-Primed lymphocytes

Mouse lymphocytes that have been primed in vitro against alloantigens show a specific increase in cells reactive to the priming antigens in mixed lymphocyte response (MLR) and include cells that are specifically cytotoxic in vitro. The primed population also contains cells capable of causing rejection of skin grafts when injected into nude mice. Functional enrichment of cells capable of rejecting skin grafts bearing specific alloantigens and depletion of cells capable of rejecting a third-party graft have been shown. Priming the cells a second time in vitro may result in a moderate enrichment of cells capable of rejecting the specific graft and depletion of cells reactive to third-party skin compared with once-primed cells. These findings support the prediction that the MLR is an in vitro model of allograft responses in vivo.

Mixed leucocyte reaction (MLR) in the snake Psammophis sibilans

In spring, spleen cells (SC) derived from outbred adult snakes, Psammophis sibilans, proliferated vigorously in mixed leucocyte cultures (MLC), thus indicating that reptiles are endowed with the subset(s) of lymphocytes capable of recognizing and responding to alloantigens. Sephadex G-10- or nylon wool-adherent latex-ingesting cells provided accessory, rather than stimulatory, function in MLC. The data, based on numerous one- and two-way MLR studies, showed that the snake P. sibilans possesses strong lymphocyte-activating determinants (LAD) which, however, appeared not to be extensively diverse, as mutually or unilaterally unresponsive SC combinations were quite often observed. Furthermore, seasonal investigations revealed that the lymphoproliferative response in MLR is considerable only in some months of spring and autumn, being abrogated during the rest of the year. These findings suggest that antigen sharing and environmental conditions greatly restrict the cell-mediated immune potential of snakes.

Anti-VH antibodies interfere with antigen binding by human T lymphocytes

The effect of antisera against a VH fragment have been investigated in several T cell proliferative assay systems. Anti-VH antisera raised in sheep, rabbits and chicken induced profound inhibition of PPD stimulated lymphoproliferation. Likewise were both mixed lymphocyte reaction (MLR) and autologous mixed lymphocyte reaction (AMLR) severely hampered while stimulation induced by mitogens was only minimally affected. Specificity testing indicates that the inhibiting antibodies in these experiments are not directed against native immunoglobulin determinants but rather against determinants specific for the VH fragment. These results thus support the notion that T cells express VH antigens and that these antigens are part of or closely associated with the antigen receptor on human T lymphocytes.

Generation of immunoglobulin secreting cells in mixed lymphocyte culture

The nature of the cellular interactions and role of the HLA system in the generation of immunoglobulin secreting cells in primary and secondary mixed lymphocyte cultures were investigated. The B lymphocyte response to alloantigen stimulation as measured by a Protein A reverse hemolytic plaque assay, consisted of polyclonal activation with production of IgG, IgM, IgA secreting cells detectable as early as day 4 in a primary and by 24 hr in a secondary mixed lymphocyte culture. B cell activation was shown to be dependent upon collaboration with T helper cells. A disparity at the HLA D/DR region between responding and stimulating cell populations was required for the induction of T helper cells. However, once activated, T helper cells could collaborate with autologous or allogeneic B lymphocytes and, without additional antigen, trigger immunoglobulin production. The mixed lymphocyte culture may now be considered a model of B cell as well as T cell activation.

Assessment of environmental contaminant-induced lymphocyte dysfunction

Although it has been established that environmental contaminants can alter immune function, the mechanisms of action have yet to be determined. This paper reviews the effects of hydrocarbon environmental contaminants on lymphocyte function and presents an approach which may serve to delineate the mechanisms of action. The approach is based on the use of the developmental phases of an immune response and assays which can be used for their functional assessment. Possible interactions between environmental contaminants and lymphocyte function and factors which must be considered in the evaluation of immune status are discussed. In addition, a study on the influence of the chronic exposure to two polyhalogenated hydrocarbons, PCB and HCB, on several parameters of lymphocyte function in mice is presented.

Polyclonal human T lymphocyte activation results in the secondary functional activation of the human B lymphocyte

The polyclonal T lymphocyte activators Con A and PHA were demonstrated to induce secretion of IgM and IgG as well as IgA antibodies in cultures of human peripheral blood lymphocytes. A similar response was seen in one-way mixed lymphocyte cultures and the kinetics, dose-response characteristics and optimal culture conditions are presented. The presence of functional T lymphocytes is a prerequisite for in vitro B lymphocyte activation in response to T lymphocyte mitogens. A narrow dose-response profile is a characteristic for both Con A and PHA and polyclonal B cell activation occurred at what have been previously regarded as suboptimal concentrations of these agents. The use of higher doses of these activators failed to generate immunoglobulin-secreting cells despite the presence of early and optimal levels of DNA synthesis in the cultures.

Effect of cyclosporin A on the generation of cytotoxic T lymphocytes in mouse mixed lymphocyte culture

Cyclosporin A inhibited at equal concentrations both the proliferative response and the generation of cytotoxic T lymphocytes in one-way mouse spleen cell mixed lymphocyte culture. The 50% inhibitory concentration was in all experiments 10(-2) to 10(-1) microgram/ml. The inhibition was directly proportional to how early the drug was added to the culture: a complete inhibition of both responses was obtained if the drug was added on day 3, and a partial inhibition if added on day 4 of culture. Cytological analysis of the cultured cells demonstrated that resting lymphocytes were not damaged at 100-1000-fold concentrations of the drug giving complete inhibition of the blastogenic response. The results suggest that cyclosporin A is most effective if present throughout the induction phase of the immune response.

Density gradient electrophoresis of mouse spleen lymphocytes: age-related differences. A critical thymus-dependent event during development in the young adult mouse

T and B BALB/c mouse spleen lymphocytes have been separated by preparative density gradient electrophoresis from animals of different ages. Significant age-related differences in the frequency of occurrence of cells exhibiting different mobility were observed in the young adult mouse. In the 6.5-week-old animals, the frequency of occurrence of the high (T lymphocytes) and low (B lymphocytes) mobility cells was changed, so that these lymphocytes exhibit an electrophoretic distribution profile different (essentially unimodal) from younger (3.5--5.5 weeks) or older (7.5--17 weeks) animals. In the latter two, bimodal electrophoretic distributions were observed. However, differences were also found in the frequency of occurrence of high and low mobility cells. The mobility distributions, representing individual cell types, were reproducible. Furthermore, the age-related changes were independent of the method of cell preparation and appeared in all mouse strains examined. Lymphocytes from animals thymectomized at the 5th week of age did not exhibit these changes (i.e. unimodal distribution) by the 6th week of age. Their electrophoretic distributions at the 6th week and thereafter were similar to those obtained from younger (3.5--5.5 weeks old) animals. It is concluded that the observed changes in the electrophoretic distributions of mouse spleen lymphocytes during development are thymus dependent and may be related to thymus involution.

Polyclonal antibody secretion induced in human mixed lymphocyte cultures. II. No direct activation of B cells

Antibody secreting B cells were measured as plaque forming cells (PFC) in a hemolysis-in-gel assay using fluorescein isothiocyanate (FITC) coupled SRBC as targets or protein A coupled SRBC as targets and developing antisera. Peak antibody secretion occurred on day 5 and the highest number of PFC was seen when mitomycin treated stimulator cells: responder cells were used in a ratio of 1:4. The number of PFC in MLC was not correlated to the DNA synthetic response. Antibody secretion in MLC was found to be of IgM, IgG and IgA classes. Significant numbers of PFC in MLC from blood lymphocytes were detected with the protein A technique, but not using FITC-SRBC targets. Compared to spleen cells, fewer PFC were stimulated in blood lymphocytes. B cells alone, enriched by rosetting of T cells, did not respond by antibody secretion or DNA synthesis in MLC. When Lipopolysaccharide (LPS) was added to MLC an additional effect was seen on the number of PFC which may indicate that distinct B cell subpopulations are activated in MLC by LPS.

Polyclonal antibody secretion induced in human mixed lymphocyte cultures

In mixed leucocyte culture (MLC), using human spleen cells or thoracic duct lymphocytes, antibody secretion was induced, measured as plaque-forming cells (PFC) in a haemolysis-in-gel assay with fluorescein isothiocyanate (FITC)-coupled sheep erythrocytes (SRBC) as targets. Peak antibody secretion was seen on day 5. Using protein-A-coupled SRBC as targets and developing antisera, antibody secretion in MLC was found to be of IgM, IgG and IgA type. There was no correlation between the number of PFC against FITC-SRBC in MLC and DNA synthesis. Supernatants from MLC failed to induce antibody secretion.

Cellular co-operation in the production of human leucocyte inhibitory factor by lymphocyte subpopulations stimulated with antigens and allogeneic cells

The ability of antigens and allogeneic cells to induce lymphokine synthesis and cellular co-operation in lymphokine production was investigated. Human peripheral blood lymphocytes were separated into T- and B-cell populations by sheep red blood cell rosette formation and centrifugation on Ficoll--Isopaque. The cells were then stimulated with PPD, SK-SD, candida and with allogeneic cells. The presence of leucocyte inhibitory factor (LIF) in the culture supernatants was tested by the agarose migration method. The results indicated that T lymphocytes produced LIF after stimulation with antigens and allogeneic cells. In addition, B cells responded to PPD. Except for PPD the stimulants did not induce significant T-cell LIF production in the absence of monocytes. Only autologous monocytes enhanced LIF synthesis after antigenic stimulation, whereas in mixed lymphocyte cultures allogeneic monocytes were as effective as autologous ones. The monocyte helper effect was mediated by soluble factors in mixed lymphocyte cultures and by soluble factors and direct cell--cell contact in antigen-stimulated cultures. No co-operation between T and B lymphocytes was found. B cells did not enhance LIF production by T cells, nor could T cells induce a B-cell response to antigens or allogeneic cells.

The cells involved in cell-mediated and transplantation immunity in the normal outbred rabbit. XIII. The identity of the responder cells and the role of phagocytic cells in the mixed leucocyte culture reaction

The ability of rabbit spleen cells depleted of thymus, bone marrow or appendix-derived cells to respond in the one-way mixed leucocyte reaction (MLR) has been investigated. The specific subpopulations of lymphoid cells were eliminated by lysis of these cells in the presence of specific antisera and complement. Phagocytic cells (monocytes and heterophils) were removed with a strong magnet after incubation with carbonyl iron particles. The results indicate that the MLR-responding cells are thymus-derived and that neither bone marrow-derived cells nor appendix-derived cells are essential for the blastogenic response following stimulation with allogeneic cells. A minimum number of phagocytic cells is required for a significant response. These cells, however, exhibit a non-specific (accessory) role and can be supplied by either the responding or the stimulating cell population.

Alloantigens derived from stimulator cells and bound onto MLC-activated rat T lymphoblasts

Rat T lymphocytes were activated in MLC (mixed leucocyte culture) against allogeneic stimulator cells. A few percent of such T blasts could be shown to carry IgM on their surface when a mixture of T and B lymphocytes was used as responder cells. The immunoglobulin was absent when purified T lymphocytes served as responders. A large proportion of MLC T lymphoblasts could be shown to carry stimulator alloantigens on their surface. These antigens were demonstrated (a) by indirect immunofluorescence using anti-stimulator alloantibody and FITC (fluorescein isothiocyanate Isomer I)-labelled F(ab)2 fragments of rabbit anti-rat Ig; (b) by autoradiography after internal labelling of stimulator cells, which showed the transfer of label from stimulator to responder cells. For biochemical analysis T blasts were restimulated with internally labelled allogeneic or syngeneic stimulator cells, and bound radiolabelled stimulator alloantigens were analysed on SDS-PAGE (sodium lauryl sulphate polyacrylamide gel electrophoresis). The results suggest that intact SD antigens with a molecular weight of 45,000 daltons and LD determinants with a molecular weight of 34,000 daltons derived from stimulator cells are found on MLC T blasts. No evidence of binding of the 27,000-dalton Ia chain to T blasts was found. Possible arrangements of these molecules on the responder blasts is discussed.

Stimulating capacity of human lymphoid cell subpopulations in mixed lymphocyte cultures

The content and yield or B cells, T cells and monocytes were investigated in cell fractions separated from human peripheral blood by various techniques. These cell fractions, which were highly enriched for either B cells, T cells or monocytes, were tested for their capacity to stimulate allogenic peripheral blood mononuclear cells in mixed lymphocyte cultures (MLC). B cells were found to be strongly stimulatory. Monocytes stimulated strongly at low stimulator/responder cell ratios, while less stimulation was observed using larger amounts of cells. T cells were demonstrated to stimulate weakly, if at all.

Mouse spleen lymphoblasts generated in vitro. Recovery in high yield and purity after floatation in dense bovine plasma albumin solutions

Mouse spleen lymphoblasts, stimulated to divide in vitro, acquired a low cell density and could be separated by isopycnic techniques. Cultured cells were suspended in BPA columns, rho = 1.080, and spun to equilibrium. The method was simple, fast, accomodated large numbers of cells, and was reproducible. It provided lymphoblasts in high yield and purity (at least 80% of the low density cells were blasts). It allowed for the recovery of proliferating cells in their first cell cycle, and did not alter the subsequent ability of cells to proliferate when recultured in vitro. Certain properties of mouse spleen lymphoblasts were analyzed in detail. Lymphoblasts induced by LPS, FCS, con A (tetravalent and succinylated), and MLC were very similar except in the absolute numbers that were induced. The blasts exhibited the classic cytologic features of enlarged nucleoli and abundant cytoplasmic polyribosomes (basophilia). As a population, they were enlarged in size relative to nondividing cells, but this seemed to apply primarily to cells in the S and G2+ M phase of the cell cycle rather than G1. The cell cycle distribution of lymphoblasts was analyzed by flow microfluorometry. By analyzing low density cells obtained at varying intervals after mitogen stimulation, FMF indicated that lymphoblasts enter the S phase of their first cell cycle beginning at 20-24 h after stimulation.

Subpopulations of cells involved in the human mixed lymphocyte culture response

Various subpopulations of human peripheral lymphoid cells were tested for their role in the mixed lymphocyte culture (MLC) response. Preparations of lymphocytes enriched for T cells, separated by a rosette sedimentation technique, were usually found to exhibit higher MLC responses than preparations enriched for B cells. The relatively high responses of B-cell-enriched preparations could largely be explained by contaminating T cells (approximately 5%) whose MLC reactivities were strongly enhanced by autologous non-T lymphocytes. Cell preparations enriched for B cells were found to be more potent stimulations of MLC responses than T-cell-enriched preparations in most responder-stimulator cell combinations. An MLC response could only be elicited in the presence of cells with characteristics of monocytes/macrophages. These cells could be derived from either the responder or the stimulator.

Cellular requirements for the induction of cytotoxic T cells in vitro

The stimulator and accessory cell requirements for the induction of cytotoxic T cell responses to alloantigens in vitro are reviewed. The ability of lymphocytes to stimulate was acquired early in development and was found to be a property of both Ig+ and Ig- cells. The presence of Fc receptors, complement receptors or Ia antigens on lymphocytes did not confer superior stimulator capacity. In contrast to lymphocytes mature macrophages were poor stimulators. When resting lymphocytes were used as a source of stimulator cells there was an additional requirement for an adherent accessory cell population for the induction of cytotoxic T cells. The accessory cell population functioned whether syngeneic or allogeneic with the responder and was required for the induction rather than the maintenance of the response. It was further characterized as an Ig+, theta, FcR+/-, CR +/-, Ia- cell which was not a mature macrophage. Accessory cells could be replaced to some extent by supernatants from spleen cell cultures. A model for T cell induction is proposed where only cells which produce unique inductive stimuli are able to function as stimulator cells. Stimulator cells are defined as those cells capable of stimulating cytotoxic T cell precursors directly and independently. Stimulator capacity is suggested to be a function of activated cells only, thus lymphocytes only stimulate following activation by accessory cells. Cells lacking innate stimulator capacity but exhibiting Ia antigens are suggested to stimulate via an alternative means.

Expression of the acid alpha-naphthyl acetate esterase marker by activated and secondary T lymphocytes in man

Acid alpha-naphthyl acetate esterase (ANAE) activity is characteristic of resting human T lymphocytes. The expression of the ANAE marker by activated human T and B lymphocytes (blasts) and by corresponding 'secondary' lymphocytes has been investigated. Human blood lymphocytes were stimulated by selective T-cell (phytohemagglutinin (PHA) and concanavalin A (Con A)) or B-cell (Staphylococcus aureus strain Cowan 1) mitogens or in the mixed lymphocyte culture (MLC), and the percentage of blasts expressing the marker was quantiated. Whereas 95% of Con-A-activated blasts expressed the marker, approximately 25%-30% of MLC-activated blasts and only 10%-25% of PHA-activated blasts were ANAE-positive. After reversion to secondary lymphocytes, the PHA- and MLC-activated cells regained the ANAE activity, and more than 90% of the blast-derived secondary T lymphocytes were ANAE-positive. Only 2%-8% of blast cells activated by Staphylococcus aureus strain Cowan 1 were ANAE-positive. We therefore conclude that ANAE is not a reliable marker for T cells when activated cells (blasts) are considered.

Identification of mouse T and B lymphocytes from cytocentrifuged cell smears

A method enabling direct enumeration of mouse T and B cells from cytocentrifuged cell smears is described. The acid alpha-naphthyl acetate esterase (ANAE) staining was used as marker for T cells. The distribution of the ANAE marker-carrying lymphocytes closely followed the percentual distribution of T cells in spleen and lymph node. Electrophoresis analysis demonstrated that while more than 95% of resting spleen and lymph node T cells carried the ANAE marker, only less than 5% of the B cells were ANAE positive. The B cells (surface-bound Ig-carrying small lymphocytes) were identified by anti-Ig serum followed by rosetting of the B cells with Staphylococcus aureus strain Cowan 1 (StaCw). The ANAE marker-carrying cells did not overlap with the StaCw rosette-forming lymphocytes. Thus we conclude that the combination of StaCw rosetting and ANAE staining enables accurate identification of resting T and B cells from a single microscope slide. Ninety to 100% of Con A-activated blasts expressed the ANAE marker but only 60-85% of PHA and MLC-activated blasts were positive. Twenty to 33% of the blast cells stimulated by LPS expressed the ANAE marker. Thus the ANAE marker is not a reliable criterion for T cells in actibated state.

Products of the major histocompatibility complex and their relationship to the immune response

The genes of the major histocompatibility complex were first known for the part they played in transplant rejection. Recently, however, it has become clear that the products of that region have an important part to play in the control of the immune response, through their effects both on cooperative and on aggressive interactions between cells. It is now possible to guess at the mechanisms which may underly the association of some major histocompatibility antigens with disease.

T and B lymphocytes. Exclusive role as responders and stimulators in human one-way mixed lymphocyte reaction

Four different combinations of one-way mixed lymphocyte reactions between human peripheral blood T and B lymphocytes (at a ratio of 1:1), purified by the E-rosetting technique, were carried our. A significant mixed lymphocyte reaction was observed only in a combination in which T lymphocytes, as responding cells, and B lymphocytes, as stimulating cells, were utilized. No significant mixed lymphocyte reaction was noted in the other three combinations of cells, using T or B lymphocytes as responders and T lymphocytes as stimulators, and also B lymphocytes as both responders and stimulators. Mixed lymphocyte reactions between T lymphocytes as responders (at constant concentration) and T and B lymphocytes as stimulators (varying proportions) showed that the response decreased proportionately with decreasing numbers of B cells and increasing numbers of T cells used as stimulators. Addition of increasing numbers of stimulating T cells to a constant number of stimulating B cells did not suppress or enhance the T-cell response to B cells. These observations indicate that the human peripheral blood T and B lymphocytes play an exclusive role as responding cells and stimulating cells, respectively.

Human thymus cells: blastogenic response to mitogens, antigens and allogeneic cells

Over 90 per cent of the thymus cells from each of twenty-six donors were T lymphocytes, identified by E-rosetting and less than 3 per cent of the cells were B lymphocytes identified by EAC-rosetting. With advancing age, the proportion of T lymphocytes decreased while that of B lymphocytes increased. The degree of (3H)thymidine incorporation of thymus cells was inversely proportional to the age of the thymus-cell donor. The PHA or PWM- induced blastogenic response of thymus cells gradually increased with advancing age when the response was expressed as the stimulation index. However, the actual rate of (3H)thymidine incorporation in all three groups was rather similar when cells were cultured with mitogens. The difference in stimulation index was due to the variation in incorporation rate in cultures without stimulants. The PHA response was approximately four-fold higher than that of PWM response. Thymus cell response to allogeneic lyphocytes, on the other hand, had no correlation with the age of thymus donor. The most surprising result in the present study was that the thymus cells from each of ten donors, aged 1-14 years, were incapable of responding to all four different recall antigens. Peripheral blood lymphocytes from nine to ten randomly selected age-matched children responded very well to one or more antigens.

Changes in the stimulatory capability of mouse small thymocytes to give a proliferation of allogenic spleen cells during differentiation

Our previous studies on surface antigenic properties of murine small thymocyte subpopulations raised the hypothesis that some of the least dense cells, which possibly were precursor T cells, differentiated into the most dense cells which have the properties of mature T cells. Thus, the stimulatory capacity of the least dense was compared with that of the most dense by one-way mixed leukocyte culture. A marked difference in capacity between both subpopulations was found, i.e., the capacity of the least dense was the strongest of all subclasses, whereas that of the most dense was the weakest. It was concluded from discussions on this difference that the finding supported the hypothesis.

Functional T cells in rabbits gut mucosal lymphocytes

Functional studies of Peyer's patch and gut mucosa lymphocytes were performed in mixed lymphocyte culture reaction (MLC), an in vitro measure of the capacity of T cells to recognize and respond to cell surface alloantigens. The data demonstrate the functional effectiveness of both these mucosal lymphocyte populations in one-way MLC, both as responding as well as stimulating cells. Both the responding and stimulating capacities of these cells in MLC were almost the same as observed for lymphocytes obtained from either spleen or thymus. We conclude that functional T cells exist in both rabbit gut lamina propria and Peyer's patches with approximately the same quantitative capacity to respond in the MLC.

Human thymus cells. Excellent responders but poor stimulators in 'One Way' mixed lymphocyte reaction

Human allogeneic 'one-way' mixed lymphocyte reactions between thymus cells and thymus cells were entirely absent. Of twenty-one mixed lymphocyte reactions between peripheral blood lymphocytes as responding cells and thymus cells as stimulating cells, only eleven had a weak but significant reaction. In contrast, a highly significant response was observed in each of eighteen mixed lymphocyte reactions between thymus cells as responding cells and peripheral blood lymphocytes as stimulating cells and in each of eleven mixed lymphocyte reactions between peripheral blood lymphocytes and peripheral blood lymphocytes. These findings indicate that the thymus cells (T lymphocytes) possess excellent proliferative capacity, with little or no stimulating capacity, while peripheral blood lymphocytes (T and B lymphocytes), on the other hand, are good responders, as well as good stimulators, in the mixed lymphocyte reaction.

Immunological responsiveness of frozen-thawed human lymphocytes

Mononuclear cells (10--20 X 10(6)) obtained from human peripheral blood by a standard Ficoll-Hypaque technique were suspended in RPMI 1640 media at 4 degrees C containing 10% foetal calf serum and 7-5% dimethyl sulphoxide (DMSO). Two-millilitre aliquots were cooled at -1 degree C/min in a Cryoson BV-4 programmed freezing system to -30 degrees C, then -5 degrees C/min to -80 degrees C and stored in liquid nitrogen vapor. On the day of testing, cell suspensions were thawed rapidly in a 37 degree C water bath. DMSO was diluted slowly out of the sample and cells resuspended in fresh RPMI 1640. It was found that frozen stored human lymphocytes (FSHL) demonstrated all the characteristics of fresh unfrozen cells. These included their ability to form spontaneous rosettes with sheep erythrocytes ('E' rosettes) and sheep erythrocyte--antibody--complement rosettes ('EAC' rosettes). The presence of surface immunoglobulins and Fc receptors were shown by membrane immunofluorescence to be comparable. In addition, the results show that FSHL respond to mitogens, specific antigens; act as both stimulators and responders in the mixed lymphocyte culture reaction; and exhibit cell-mediated lymphocytotoxicity following in vitro sensitization, or against antibody-coated target cells.

Inhibition of mixed leukocyte culture by anti-idiotypic antibodies

(CBA x C57BL/6)F1 antisera prepared by injecting F1 mice with CBA T lymphocytes or CBA anti-C57BL/6 alloantibodies were tested for their ability to inhibit the mixed leukocyte culture (MLC) response. Presence of antiserum throughout the culture period in the absence of complement did not have any effect on the MLC response. Treatment of CBA responder cells with F1 antiserum and complement prior to the culture specifically inhibited the MLC response. Specificity of the suppression was ascertained; absorption of the F1 sera with F1 or C57BL/6 spleen cells did not remove the suppressive factor, whereas absorption with CBA spleen cells did so. F1 antiserum treatment left intact the response to third party alloantigens (DBA/2). Immunabsorbent columns with alloantibody of corresponding specificity removed the suppressive factor from anti-T cell sera as well as from antisera to alloantibody. The data suggest that the circulating alloantibody population contains molecules which share idiotypic determinants with surface receptors on T cells recognizing the same alloantigens.