In vitro proliferative response of chronic lymphocytic leukemia

Summary The peripheral blood lymphocytes of 13 previously untreated chronic lymphocytic leukemia (CLL) patients showed a decreased and delayed responsein vitro to plant mitogens (PHA and PWM) and specific antigens (PPD and MLC). In addition, the serum of these patients inhibited the mitotic reactivity of both autologous and homologous normal lymphocytes. Since incubation with CLL serum did not affect the SRBC-rosetting capacity of normal lymphocytes, we believe that CLL serum interferes with some metabolic stage in blastogenesis rather than at the level of mitogen membrane interaction. Thein vitro transformation of lymph node, bone marrow and peripheral blood lymphocytes in some of these patients was also investigated. Stimulation of peripheral blood cells with plant mitogens resulted in a more serious impairment of the response than that found with bone marrow and lymph node cells. This could be explained by the fact that, although CLL is a widespread lymphoproliferative disorder, some preferential homing of normally reactive cells in the bone marrow and lymph nodes cannot be excluded. Finally, since no stimulation was observed in mixed leukocyte cultures (MLC), our experiments provide evidence that no antigenic differences are detectable in CLL lymphoid populations.     

Phenotypic analysis of human peripheral blood lymphocytes by automatic sampling flow cytometry after stimulation with mitogens or allogeneic cells

Summary Human peripheral blood lymphocyte (PBL) phenotypes have been analyzed before and after stimulation with phytohemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM) for 3 days and in mixed lymphocyte culture (MLC) for 7 days. PBL labeled with each of 10 fluorescent monoclonal antibodies were automatically sampled for flow cytometry from 96-well microtiter plates using a microsample delivery system. The reference phenotypic ranges were determined in fresh cells and control cultures. PHA was mostly mitogenic for T PBL bearing the CD3, CD5, CD7, CD8 and CD25 differentiation clusters, and a low density of CD1 and CD4 had a small effect on human natural killer cells (HNK) and also did not stimulate B (CD19) and HLA-DR⁺ PBL. There was an incomplete phenotypic overlapping between PHA- and ConA-stimulated cultures, ConA being more mitogenic for CD4 and less mitogenic for CD8 PBL. The mitogenic effect of PWM was evident on CD3, CD5, CD7, CD4, CD25 and CD8, but not on HNK, HLA-DR and CD19 B PBL, which presumably had already differentiated into antibody-secreting cells. After MLC stimulation all T, B and HNK PBL subsets tested were increased, but the cells bearing CD1, CD4, CD5, CD7, CD25, HNK, CD19 and HLA-DR had the greatest proliferation with respect to the unmixed control PBL. The present approach to the phenotyping of PBL subsets could offer more complete and accurate data for monitoring and follow-up of patients in transplantation and immunopathology hospital wards. This work was supported in part by grants from theConsiglio Nazionale delle Ricerche (CNR), Roma, Italy,Progetto Finalizzato ‘Oncologia’, theAssociazione Italiana per la Ricerca sul Cancro (AIRC), and theAssociazione per le Ricerche Biomediche, Verona, Italy.     

Cytochalasin B is a potent mitogen for chronic lymphocytic leukemia cells in vitro.

It is widely accepted that the neoplastic B cells from patients with chronic lymphocytic leukemia (CLL) respond poorly to common mitogens. The fungal metabolite cytochalasin B (0.5 micrograms/ml) is a weak mitogen for normal lymphocytes. However, when peripheral blood lymphocytes from 19 patients with CLL of B cell origin (B-CLL) were cultured with 0.5 micrograms cytochalasin B/ml, significant new DNA synthesis ( [14C]thymidine incorporation) occurred in 18. Stimulation indices with cytochalasin B varied widely (range = 1.9-28.2, mean +/- SD = 10.6 +/- 7.5; delta cpm range = 1,157-153,818; n = 26) but in 11 cases exceeded those seen with concanavalin A (Con A), phytohemagglutinin, or pokeweed mitogen. In all 11, the mitogenic response to cytochalasin B exceeded that to pokeweed mitogen, which is believed to be a T cell-dependent B cell mitogen. In three cases, the responses to cytochalasin B were 8.6, 3.5, and 2.3 times greater than those to Con A. As with other mitogens, the DNA synthetic response to cytochalasin B was time and dose dependent. Peak thymidine incorporation occurred at 72-88 h and declined thereafter. Significant mitogenic effects were observed with 0.1-5 micrograms cytochalasin B/ml with a peak at 0.5-2 micrograms/ml. Stimulated DNA synthesis was abolished by 1 mM hydroxyurea. Cells from two patients with B-CLL were separated by rosetting with sheep erythrocytes (E). Depletion of E-rosette-positive cells from the CLL cell population abolished the response to Con A but did not affect the response to cytochalasin B. Cytochalasin B is a potent mitogen for B-CLL cells and may be useful in cytogenetic studies of this often indolent neoplasm.     

The role of arachidonic acid metabolite PGE2 on T cell proliferative response

We have examined the role of cyclooxygenase and lipooxygenase-derived metabolites of arachidonic acid (AA) during T cell activation. One of the major products of cyclooxygenase activity is prostaglandin E2 (PGE2). As is known, macrophages (Mo) are the main PGE2 producer cells among the peripheral blood mononuclear cells (PBL) and can be induced to release PGE2 during T cell activation. On culturing PBL with T cell mitogens such as phytohemagglutinin (PHA) or monoclonal antibody OKT3, the levels of PGE2 produced by Mo were positively correlated with the entity of the T cell mitogenic signal. During T cell activation, subcellular factors able to provide positive or negative signals on the Mo PGE2 production are released in culture. We observed that recombinant IL2 strongly enhanced PGE2 synthesis in lipopolysaccharide (LPS) stimulated Mo culture, while recombinant interferon gamma (IFN-gamma) partially inhibited its production. Moreover, purified IL1 induced PGE2 synthesis in resting Mo and increased its production when Mo were activated by LPS. The PGE2 released during T cell activation seems to have no effect on T cell mitogenesis, since the addition of cyclooxygenase inhibitors did not influence the proliferative response of mitogen stimulated T cells. However, the addition of PGE2 to OKT3 stimulated PBL at the beginning of the culture period inhibited the proliferative response in a dose-dependent manner. Its addition had no effect on PHA-stimulated PBL cultures. The PGE2-dependent inhibition of OKT3-induced T cell proliferation declined progressively from about 50-10% as the addition of PGE2 was delayed from 0 to 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)     

T lymphocyte subpopulations in the bone marrow and peripheral blood of untreated patients with myeloma

Summary The quantitative distribution of the two main T lymphocyte subsets, recognizable by the ‘high’ and ‘low-affinity’ E rosette-forming cell technique of West, was studied in both the bone marrow and peripheral blood from ten untreated multiple myeloma (MM) patients. A reduced total T lymphocyte count, with a relative predominance of ‘low-affinity’ T lymphocytes (putative suppressor T cells), was found in the peripheral blood. Within a normal total T lymphoid cell count, a predominance of the T lymphocyte subset with ‘low-affinity’ characteristics was also observed in the bone marrow. An inverse correlation, that was statistically significant, was seen between the monoclonal malignant cellular B component and the ‘low-affinity’ T cell percentage in all cases. It is concluded, therefore, that such an imbalance between the ‘high’ and ‘low-affinity’ T subsets, with the latter predominating, could be of importance in the regulation of the growth rate of the monoclonal cellular B component.     

Soluble factor(s) released by Concanavalin A activated lymph node lymphocytes induce proliferation and maturation of chronic lymphocytic leukaemia (CLL) B lymphocytes

An active supernatant (Ly Con A) was prepared by stimulating the normal human lymph node lymphocytes with Concanavalin A (Con A). Peripheral blood lymphocytes (PBL) from 3 healthy subjects and from 8 patients with chronic lymphocytic leukaemia (CLL) were cultured in the presence of Con A and Ly Con A. The latter induced a significant DNA synthesis both in normal and CLL lymphocytes. A proliferative response was still present in CLL after T lymphocytes depletion. The Con A and Ly Con A treatment also induced morphological changes in CLL lymphocytes consistent with plasma cell differentiation. In 3 cases the appearance of cytoplasmic light chains was detected by immunofluorescence. These findings suggest that peripheral blood B lymphocytes from CLL patients can be stimulated to maturation when helper factor(s) released by mitogen activated lymph node lymphocytes are provided.     

Interleukin-2-Induced proliferation of CD4-CD8- human thymocytes.In vitro expression of CD3 and CD8 antigens and cytolytic activity

Human thymocytes lacking both CD4 and CD8 differentiation antigens were prepared by treating total thymocyte suspensions with a mixture of anti-CD4 and anti-CD8 monoclonal antibodies and complement. The resulting populations contained less than 2% CD4⁺, CD8⁺ or WT31⁺ cells and variable percentages (less than 20%) of CD3⁺ cells. These cell populations were cultured in recombinant IL-2 in the presence of peripheral blood mononuclear cells as feeder cells. Cells underwent extensive proliferation accompanied by a progressive increase of CD3⁺ and CD8⁺ cells. On the other hand, appearance of neither WT31⁺, α/β-positive T cell receptor (TCR), nor CD4⁺ cells could be observed in several independent experiments. Functional analyses revealed the appearance and the progressive increase of cytolytic activity against the natural killer (NK)-sensitive K562 cells as well as the NK-resistant fresh melanoma cells. Experiments of T cell cloning indicated that both the expression of CD8 and CD3 antigens and the appearance of cytolytic activity were consequent to cell maturation occurring at the level of CD4^-CD8^- non-cytolytic cell precursors. In these experiments, more than 30% of cells underwent clonal expansion and all the clonal progenies obtained displayed cytolytic activity and expressed the CD3⁺WT31^- surface phenotype. The expression of CD8 was variable, whereas no CD4⁺ clones could be obtained. Cells expressing such surface phenotype are known to belong to the TCR γ-positive T lymphocyte subset lacking the typical α/β TCR and thus appear to be the only T cell type capable ofin vitro proliferation and maturation under easily reproducible culture conditions. This work was supported by grants awarded by the Consiglio Nazionale delle Ricerche (CNR), Roma, Italy, Progetto Finalizzato ‘Oncologia’ to M. C. M. and L. M. A fellowship by Associazione Italiana per la Ricerca sul Cancro (AIRC) was awarded to A. M.     

STIMULATED LYMPHOCYTE CULTURES : RESPONDER RECRUITMENT AND CELL CYCLE KINETICS

Lymphocytes, stimulated with different doses of plant mitogens or allogeneic cells, incorporate varying amounts of [³H]thymidine. Theoretically, this may be due to different numbers of responding cells, to earlier proliferative response of these cells, and/or to their more or less rapid transit through the cell cycle. Dog peripheral blood lymphocytes were stimulated in vitro with different doses of phytohemagglutinin (PHA), or with allogeneic lymphocytes. After their synchronization by incubation with hydroxyurea (4 mM), the mean durations of the cell cycle, and of the different cell cycle phases were constant and unrelated to strength or type of stimulation. PHA-stimulated lymphocyte cultures were maintained in the presence of colchicine, to prevent clonal proliferation of responding lymphocytes. DNA uptake in this setting, attributed to first generation responders, was related to the strength of proliferative lymphocyte response in control cultures without colchicine. Furthermore, cell proliferation occurred earlier with greater stimulation. It is concluded that higher [³H]thymidine uptake in vitro by stimulated lymphocytes is due to greater numbers of responding cells, which are triggered into proliferative response earlier, and not to a more rapid transit of the responding cells through the cell cycle.     

Thymic origin of some natural killer cells: clonal proliferation of human CD3−16+ cells from CD3−4−8− thymocyte precursors requires the presence of H9 leukemic cells

Summary Purified CD3⁻4⁻ thymocyte populations were cultured in the presenceof interleukin-2 (IL-2) and peripheral blood lymphocytes (PBL) and/or tumor cell lines as a source of irradiated feeder cells. Maximal cell proliferation was obtained in the presence of a mixture of H9 leukemic cells and normal PBL. More importantly, under these culture conditions 30%–50% of these cells were found to express CD16 surface antigen after 1–2 weeks of culture. Similar proportions of CD16⁺ cells could be detected in CD3⁻4⁻ thymocyte populations that had been further depleted of CD16⁺ cells. Cloning of CD3⁻4⁻16⁻ thymocytes under limiting dilution conditions resulted, in the presence of H9 cells, in more than 50% of CD16⁺ clones (cloning efficiency 3%–8%). Since some of the surface CD3⁻ clones expressed cytoplasmic CD3 antigen, it has been possible to identify four distinct phenotypic groups of clones (CD16⁺ cyCD3⁺, CD16⁺ cyCD3⁻, CD16⁻ cyCD3⁺, CD16⁻ cyCD3⁻). Independently of their phenotype, all thymus-derived CD3⁻ clones expressed a strong cytolytic activity against natural killer (NK)-sensitive and NK-resistant tumour target cells. In addition, following stimulation with phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (or PHA alone) all clones released interferon-γ and tumour necrosis factor-α, but not IL-2. Taken together, our data provide evidence that cells which share their phenotypic and functional properties with CD3⁻ CD16⁺ NK cells can be derived from thymic precursors.     

Both CD8+ and CD16+ human T cell clones can provide B cell help for immunoglobulin production

Summary The functional properties of two CD4⁺CD8⁻CD16⁻, five CD4⁻CD8⁺CD16⁻ and three CD4⁻CD8⁻CD16⁺ human T cell clones were compared. All CD4⁻ T cell clones displayed strong cytolytic activity in the lectin-dependent lytic assay against the P815 murine mastocytoma cell line, but only the CD4⁻CD8⁻CD16⁺ T cell clones exhibited lytic activity against the natural killer-sensitive K562 cell line. Upon activation with anti-CD3 monoclonal antibody, all T cell clones were able to support IgM and IgA synthesis in autologous B cells. Both CD4⁺ and CD4⁻ T cell clones required cell-to-cell interaction with the B cells in order to exert their helper activity for immunoglobulin production. However, unlike CD4⁺, CD4⁻CD8⁺CD16⁻ and CD4⁻CD8⁻CD16⁺ T cell clones provided helper function for immunoglobulin synthesis only when low T/B cell ratios were used in culture. At higher T/B cell ratios, there was a decline in the B cell helper activity of CD4⁻ T cell clones that was probably related to the expression of cytolytic capacity against the antigen-presenting B cell. These data support the notion that under certain experimental conditions even cytotoxic T lymphocytes and natural killer cells may provide B cell helper function.     

The Mitogenic Effect of the Lymphocytosis Promoting Factor from Bordetella Pertussis on Human Lymphocytes

The purified lymphocytosis promoting factor (LPF) from Bordetella pertussis was found to be a potent mitogen for peripheral blood lymphocytes (PBL) from normal adults as well as for cord blood lymphocytes. Proliferation occurred in autologous plasma or fetal calf serum, regardless of previous exposure to pertussis infection or immunization. Only one adult human serum, from a physician constantly working with B. pertussis, inhibited the mitogenic response to LPF and this serum was shown to contain precipitating antibody against LPF. The proliferative effect of LPF was characteristic of a "nonspecific" mitogen and not of antigen stimulation of sensitized cells.LPF, phytohemagglutinin, and concanavalin A were approximately equal in potency although variation occurred depending upon the cell donor. Experiments with lymphocyte subpopulations obtained by rosetting techniques employing sheep erythrocytes, mouse erythrocytes, and sheep erythrocytes coated with antibody and complement suggested the requirement of a multicellular system for LPF mitogencity.PBL from most patients with chronic lymphatic leukemia and lymphosarcoma cell leukemia were even less responsive to LPF than to phytohemagglutinin, whereas PBL from patients with lymphosarcoma usually responded to both mitogens. It can be inferred from the results of experiments with both normal and leukemic cells that LPF, which is a murine thymus-derived (T)-cell mitogen, is also a T-cell mitogen for human PBL. The exact cell requirement and mode of action, however, are as yet unknown.     

Production of human heterophile antibodies. III. In vitro specific stimulation and immortalization of human lymphocytes

The production of primary human specific antibody against an exogenous antigen by in vitro system was achieved in this study. Human lymphocytes were prepared from the lymphocytes of human spleen (SPL), tonsil (TL), and peripheral blood (PBL). These lymphocytes were stimulated by sheep red blood cells (SRBC) co-cultured with the appropriate number of allogeneic lymphocytes or fractionated T cells. Significant numbers of plaque forming cells (PFC) against SRBC were obtained. A major population of PFC responded to the stimulator RBC and a minor population of PFC responded to both SRBC and bovine red blood cells (BRBC). The culture of allogeneic combination of whole SPL or TL stimulated with SRBC produced PFC, but not that of whole PBL. Reconstitution of equal numbers of allogeneic separated B cells and T cells from PBL was required for a significant response. These specific antibody forming cells (AFC) were immortalized by Epstein Barr virus (EBV) infection and culture supernatant containing antigen-specific antibodies (anti-SRBC: Forssman antibody) were obtained after repeated cloning.     

Ontogenetic aspects of the intestinal immune system in man

Summary The development of the mucosal immune system in the human fetus has been studied in some detail. Aggregates of T and B cells form early Peyer’s patches by 16 weeks gestation and by 19 weeks organised Peyer’s patches with T and B cell zones are seen. T cells populate the mucosal lamina propria and epithelium from 11 weeks gestation and increase in number thereafter. As in the adult, most intraepithelial lymphocytes are CD8⁺ and most lamina propria T cells are CD4⁺. By 20 weeks, villus epithelial cells are HLA-DR⁺. By 20 weeks, villus epithelial cells are HLA-DR⁺ and secretory component is also expressed. In the absence of lumenal stimulation in the fetus there is no intestinal secretory IgA antibody response. A few IgA plasma cells are present in fetal salivary glands but the number does not dramatically increase until after birth.     

Distinct mitogens reveal different mechanisms of suppressor activity in human cord blood

We have studied the suppressive ability of human cord blood lymphoid cells in a three-days mixed lymphocyte culture proliferation assay stimulated by mitogen. Sex chromosomes served as markers for dividing cord (male) or maternal cells. Three distinct mitogenic agents were used in the co-cultures: the mitogenic lectin PHA, the anti-CD3 monoclonal antibody OKT3, and 12-0-tetradecanoyl-13-acetate (TPA), a direct activator of protein kinase C. With all mitogens we observed significant, non-specific suppression of maternal/adult cell division. However, three separate levels of suppression were evident. PHA-stimulated co-cultures always showed the highest amount of cold suppressor activity (mean +/- SEM: 64.9 +/- 3.9). The mean suppression in OKT3- and TPA-stimulated co-cultures was 34.7 +/- 6.0 and 22.0 +/- 4.1%, respectively. Furthermore, indomethacin, a prostaglandin (PG) synthetase inhibitor, reduced by 41% the suppression in PHA-driven co-cultures, whereas having no significant effect on the corresponding OKT3-driven co-cultures. Our results indicate the existence of an indomethacine-sensitive, PG-dependent mechanism and a separate, indomethacine-resistant, mechanism of cord cell suppression.     

Depressed primary in vitro antibody response in untreated systemic lupus erythematosus. T helper cell defect and lack of defective suppressor cell function.

The in vitro antibody response of peripheral blood lymphocytes (PBL) from 19 patients with untreated systemic lupus erythematosus (SLE) was compared with that of 20 control patients and 44 normal subjects. Trinitrophenyl polyacrylamide beads (TNP-PAA) were used to induce IgM anti-TNP plaque-forming cells. SLE patients displayed a markedly depressed, and in most instances virtually absent, response. This was not due to an unusual kinetics of the response; nor could it be induced by preincubation of SLE patients' PBL. In co-cultures of SLE patients and normal PBL, the former, with few exceptions, did not exert a suppressive effect. In four patients the anti-TNP response of either unfractionated or T-depleted SLE PBL could be restored by T cells from a normal individual. Conversely in three of these patients, SLE T cells could not support the response of normal B cells, suggesting a T helper cell defect in SLE PBL. Concanavalin A (Con A)-induced suppressor cells of the antibody response could be assayed by two approaches: (a) in responder SLE patients, by the direct addition of Con A to TNP-PAA-stimulated cultures; (b) in seven patients by transfer of Con A-activated cells to the responding culture of a normal allogeneic donor. In both cases SLE PBL were able to exert a suppressive effect to the same extent as normal PBL.     

Immunohistopathogenesis of persistent generalized lymphadenopathy in HIV-positive patients

Persistent generalized lymphadenopathy (PGL) is a reactive lymphadenitis affecting HIV-positive patients; furthermore, PGL is often a prodrome of AIDS-related complex and AIDS. In the present review the authors describe the histology and the immunohistochemistry of lymph nodes of patients affected by PGL. Histologic alterations of lymph nodes with PGL are classified according to three main types: follicular hyperplasia without or with follicular fragmentation, follicular involution and follicular depletion. Immunohistology demonstrates a peculiar infiltration of CD3⁺/CD4⁺ and CD3⁺/CD8⁺ lymphocytes in germinal centers; CD3⁺/CD8⁺ are often grouped in small clusters centered by a newly formed small blood vessel. Accessory follicular dendritic reticulum cells (FDRCs) of germinal centers are characterized by a positive staining for p24 and p19 HIV major core antigens. In germinal centers, FDRCs undergo progressive lysis in follicular involution and in follicular depletion. Other viral antigens, such as EBV, are infrequently seen in lymph nodes from HIV-positive patients. Paracortical areas of lymph nodes are often characterized by prominent postcapillary venule proliferations and by hyperplasia of the endothelial cells which are HLA-DR positive, often p19 and p24 positive, and occasionally express HIV genome. In conclusion, in PGL the histologic changes correlate well with the immunohistologic features; accordingly, PGL might be considered the result of abnormal immune reactions to several stimuli still incompletely known. This work was supported by grants from theMinistero della Sanità, ‘Progetto AIDS’ (contract n№ 87.003), and theCassa di Risparmio di Roma, Italy.     

Formation of multinucleated giant cells from human monocyte precursors. Mediation by a soluble protein from antigen-and mitogen-stimulated lymphocytes

Multinucleated giant cells are associated with granulomas arising from immunological and nonimmunological inflammatory reactions. They are an integral part of the host immune response to chronic infectious diseases. In the present study we have demonstrated that human lymphocytes when stimulated by specific antigens of T cell mitogens produce a soluble factor that causes peripheral blood monocytes to fuse and form multinucleated giant cells in vitro. Production of the giant cell factor by antigen-stimulated peripheral blood lymphocytes correlates with the existence of cell-mediated immunity to specific antigen. Monocyte-depleted blood lymphocytes, but not purified blood monocytes, produce the giant cell factor when cultured with antigens or T cell mitogens. Gel filtration and physiochemical studies indicate that the lymphocyte-derived giant cell factor is a heat-labile protein of approximately 60,000 mol wt. These findings suggest that multinucleated giant cells in granulomas may be formed by fusion of circulating monocytes in response to the release of a 60,000-mol wt protein from antigen-stimulated T lymphocytes.     

Partial inefficiency of T cell receptors γ/δ composed of a heavy (55-kD) γ chain to mediate cell activation upon binding to specific monoclonal antibodies

Summary We analyzed CD8⁺ T cell receptor (TCR) γ/δ⁺ (δ-TCS-1 reactive) cell clones expressing the 55-kD γ chain for their susceptibility to triggering by monoclonal antibodies (mAbs) specific for TCR or CD3 molecules. Clones were derived by limiting dilution from CD3⁺, WT31⁻ FACS-purified peripheral blood populations or CD4⁻CD8⁻ thymocytes (a fraction of the latter cells expressingde novo CD8 surface antigen upon culture in IL-2). Clones were screened according to their reactivity with both anti-CD8 and δ-TCS-1 mAbs. Analysis of CD3-associated molecules immunoprecipitated by anti-Leu-4 (anti-CD3) mAb under conditions which preserve the CD3/TCR association (1% digitonin) showed a predominant 55–60-kD molecule both under reducing and non-reducing conditions. All clones expressing the δ-TCS-1⁺ CD8⁺ surface phenotype derived from either thymus or peripheral blood lysed the Fcγ receptor-bearing P815 target cells in the presence of anti-CD3 mAb. On the other hand, δ-TCS-1 mAb was poorly efficient in triggering the lytic machinery of these clones, while it induced target cell lysis by δ-TCS-1⁺ CD8⁻ clones. This work was supported by grants from theConsiglio Nazionale delle Ricerche (CNR), Roma, Italy,Progetto Finalizzato ‘Oncologia’ to M. C. M. and A. M., and from theAssociazione Italiana per la Ricerca sul Cancro (AIRC).     

Alterations of both responder T cells and stimulator non-T cells are responsible for abnormal mixed lymphocyte reaction in aged humans

Summary The autologous and allogeneic mixed lymphocyte reactions of 15 young and 15 aged human adults were compared. Both autologous and allogeneic mixed lymphocyte reactions were significantly reduced in the aged group. T cells from aged adults displayed a reduced proliferative response to non-T cells of either aged or young adults. T cells from young adults also showed a reduced proliferative response to non-T cells from aged adults. Sera from aged adults, showing depression of autologous and allogeneic mixed lymphocyte reaction, did not exert any inhibitory effect on the autologous and allogeneic mixed reaction of lymphocytes from young donors. These data suggest that depression of mixed lymphocyte reaction in aged humans probably reflects intrinsic abnormalities of both responder T cells and stimulatory non-T cells. This work was supported by a grant from theConsiglio Nazionale delle Ricerche (CNR), Roma, Italy ‘Progetto Finalizzato Medicina Preventiva, Sottoprogetto Meccanissmi di Invecchiamento’.     

Characterization of human T cells reactive with the Mycoplasma arthritidis-derived superantigen (MAM): generation of a monoclonal antibody against V beta 17, the T cell receptor gene product expressed by a large fraction of MAM-reactive human T cells

While all known microbial superantigens are mitogenic for human peripheral blood lymphocytes (PBL), the functional response induced by Mycoplasma arthritidis-derived superantigen (MAM) is unique in that MAM stimulation of PBL consistently results in T cell-dependent B cell activation characterized by polyclonal IgM and IgG production. These immunostimulatory effects of MAM on the humoral arm of the human immune system warranted a more precise characterization of MAM-reactive human T cells. Using an uncloned MAM reactive human T cell line as immunogen, we have generated a monoclonal antibody (mAb) (termed C1) specific for the T cell receptor V beta gene expressed by the major fraction of MAM- reactive human T cells, V beta 17. In addition, a V beta 17- MAM- reactive T cell population exists, assessed by MAM, induced T cell proliferation and cytotoxic T cell activity. mAb C1 will be useful in characterizing the functional properties of V beta 17+ T cells and their potential role in autoimmune disease.