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This study was undertaken to clarify the mechanism behind the severely decreased lymphocyte proliferative response upon stimulation with mitogens and antigens seen after allogeneic bone marrow transplantation (BMT) in man. We investigated eight BMT patients and eight controls and found that the proliferative response of patient cells was reduced both when the cells were stimulated with phytohaemagglutinin (PHA) and when they were stimulated with a combination of phorbol myristate acetate (PMA), which is an activator of protein kinase C (PKC), and the calcium ionophore A23187, which irreversibly opens for calcium transport into the cell (median relative responses were 41 and 37%, respectively). However, the PHA-induced increase in the concentration of intracellular free calcium in post-BMT cells was not significantly different from the values found in control cells and the expression of interleukin 2 (IL-2) receptors (CD25) was only slightly decreased. However, the production of IL-2 was severely decreased in patient cells after stimulation with A23187/PMA (median 3541 units), although it was higher than in PHA-stimulated control cells (median 354 units). These results show that a direct activation of PKC by PMA combined with an increase in intracellular free calcium by A23187 cannot overcome the lymphocyte proliferation deficiency in cells from patients after allogeneic BMT. The data suggest that the defect is affecting the diacylglycerol pathway considerably more than the inositol triphosphate pathway. [ABSTRACT FROM AUTHOR]

Recent investigations have demonstrated that the primary mixed lymphocyte reaction (MLR) is dependent on certain accessory molecules, e.g. CD4 and LFA-1, We have compared the requirements of the primary MLR and the responses of alloreactive, primed lymphocytes (PL) by inhibition studies using monoclonal antibodies (MoAb) directed against (i) adhesion molecules belonging to the CD11 cluster of leucocyte antigens (CD11a, LFA-1; CD11b, MAC1=CR3; and CD11c, p 150,95); (ii) various T cell-related antigens (CD2, CD4, CD5 and CD8) and (iii) recombinant IL-1β. The CD5-, CD11a- and CD11c-reactive MoAb significantly inhibited the primary MLR (inhibition=25%, P≤0.01; 48%, P≤0.01 and 13%, P≤0.05, respectively) but these MoAb did not inhibit the primed lymphocyte reaction (PLR). The CD11b-reactive MoAb had no significant influence on either of the responses. CD2- and CD4-reactive MoAb significantly inhibited both primary MLR (>80%, P≤0.01) and to a lesser extent the PLR (40–65%, P≤0.01). A MoAb reactive with IL-1β inhibited the primary MLR (38%, P<0.01) and the purified protein derivative (PPD) induced lymphocyte transformation response (42%, P≤0.01) of peripheral blood mononuclear cells (PBMC), whereas primed allogeneic responses to PBMC and Epstein-Barr virus (EBV) cell lines were unaffected by this MoAb. In addition, preliminary data indicated that PL seemed neither to bind exogenous IL-1 (as opposed to CD4+ PBMC) nor to possess membrane-bound IL-1. The differences between ‘virgin’ and primed, allogeneic T-cell responses indicate that profound changes in the functional capability of the responding T-cell population take place during the bulk expansion. The results indicate that during repeated priming with alloantigen and bulk expansion, the proliferative response of T lymphocytes becomes independent of (i) the interaction with the CD11 adhesion molecule(s), (ii) the CDS molecule, and (iii) the cytokine IL-1β. [ABSTRACT FROM AUTHOR]

Lymphocytes from 21 patients sampled 1–6 months after bone marrow transplantation (BMT) were tested for functional suppressor activity against marrow-donor lymphocytes in the lymphocyte transformation test. Suppression of donor responses to allogeneic (i.e. mixed lymphocyte reaction, MLR) and antigenic stimulation by irradiated (7600 rad) post-BMT cells was observed in about two-thirds of the combinations tested (N=20 and N=9). The suppression of donor MLR and antigen responses ranged between 5–52% and 10–46%, respectively. Irradiated post-BMT cells significantly suppressed donor responses to suboptimal concentrations of phytohaemagglutinin (PHA) (median suppression: 28%; P<0.05; N=7) and concanavalin A (Con A) (median suppression: 31%; P<0.05; N=6). A clearly suppressive effect of post-BMT cells was observed when the ratios of CD4-/CD8+ post-BMT cells were lower than 0.5 (P<0.01). In three experiments, the depletion of the CD8- but not of the CD4-positive subset abrogated the suppression of the donor MLR by post-BMT cells. The suppression by post-BMT cells (irradiated) of MLR and mitogen responses was comparable whether the responding cells were derived from the donor or from HLA-DR-incompatible, unrelated individuals. The proliferative capacity of post-BMT cells compared to that of donor cells was assayed in the MLR with unrelated, HLA-DR-incompatible stimulator cells. A significantly decreased proliferative capacity (median 20% of that of donor cells) was found (P<0.01; N=16). A weak inverse correlation (P<0.05; N=16) between the proliferative and the suppressive capacity of post-BMT cells in the MLR was observed. These findings indicate that the decreased proliferative capacity upon mitogen, antigen, and alloantigen stimulation observed in most patients within 1–6 months after BMT may be partly due to non-specific suppression by CD8+ cells. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the relation between the histopathological findings in LAV/HTLV-III lymphadenitis and immunological, clinical, and serological variables. The study group included 38 consecutive homosexual men with persistent generalized lymphadenopathy (PGL) in whom lymph node biopsy was performed. The histopathological lymph node changes were grouped into three stages. Opportunistic infections at the time of biopsy and their development during follow-up were significantly associated with stage III histology (follicular depletion). Analysis of blood from 10 patients with stage III histology revealed significantly (P<0.01) decreased proliferative responses of lymphocytes to mitogens and reduced absolute number of CD5+ and CD4+ lymphocytes compared with 17 patients with stage I histology (follicular hyperplasia), whereas patients with stage II histology (follicular involution) had intermediate values. The absolute number of CD8+ lymphocytes was increased in all three stages, as was IgG, while increase in IgM and IgA was restricted to stage III. No difference was observed between the different histopathological stages with respect to the specificity of the anti-LAV/HTLV-III antibody as measured by immunoblotting. In conclusion, the defects of lymphocytes from the blood of LAV/HTLV-III infected persons reflect alterations in secondary lymphoid tissue. Further, there is a close correlation between these alterations and the clinical status of the patients. [ABSTRACT FROM AUTHOR]

The in vitro immune response of lymphocytes from uraemic patients was studied by comparing the in vitro kinetics of interleukin 2 (IL-2) production. the mitogen-induced proliferative response, and the expression of IL-2 receptors by T lymphocytes The IL-2 production in 26 uraemic cell cultures decreased significantly after 48 h of stimulation with mitogen compared with that of 24 control cultures. The lymphocyte responses to phytohaemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) increased linearly with time, but the response of the uraemic cell cultures were significantly lower than those of the control cultures. The relative numbers of cells double-stained for both Tac (IL-2 receptor)/HLA-DR or Tac/Leu 2 were significantly increased in the uraemic cultures as compared with the control cultures at 48 and 72 h. A similar, but not significant. trend was also demonstrated for uraemic cells positive for Tac/Leu 3. These findings were also seen in uraemic lymphocytes cultures supplemented with exogenous IL-2. Thus, the IL-2 production of uraemic lymphocytes seems to be exhausted more rapidly than that of normal lymphocytes. and there is no evidence that the poor proliferative response of uraemic lymphocytes is due to a decreased relative number of cells positive for IL-2 receptors. [ABSTRACT FROM AUTHOR]

The lymphocyte transformation responses lo mitogens (phytohaemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM)), allogeneic cells, and the antigen-purified protein derivative (PPD) were studied in six acquired immunodeficiency syndrome (AIDS) patients and in six healthy controls, each of whom was HLA-DR- and mixed lymphocyte culture (MLC)-identical with one of the AIDS patients. No evidence of suppression was observed when irradiated or non-irradiated AIDS peripheral blood mononuclear cells (PBMC) were added to cultures of HLA-DR-identical PMBC from healthy controls stimulated with the strong milogens PHA and Con A or with allogeneic cells, but suppression may be involved in the decreased responses in cultures stimulated with PWM or PPD, Addition of supernatants from macrocultures of AIDS cells did mil suppress responses of control PBMC. Thus, suppression by any lymphocyte subset or soluble factor alone cannot explain the generally severely depressed transformation responses in AIDS. Addition of heavily irradiated HLA-DR-identical PBMC from healthy controls or supernatants from these cultures led to increased responses in cultures of mitogen-stimulated AIDS PBMC and in some cultures of antigen or allogeneic cell-stimulated AIDS PBMC. which were of the same magnitude as seen after the addition of commercially obtained T-cell growth factor (TCGF). This indicates that AIDS cells are deficient in producing TCGF. Heavily irradiated AIDS PBMC were capable of restoring the transformation responses to mitogens and antigens of purified HLA-DR-identical normal T cells, indicating that AIDS cells have a normal antigen-presenting capacity and interleukin (IL-1) production. However, AIDS PBMC had a very poor capacity to stimulate normal PBMC in MLC. Together, our experiments suggest that the immune deficiency in AIDS cells may be partially due to a decreased capability of T lymphocytes to produce TCGF and that a decreased number and/or function of dendritic cells may also be involved. [ABSTRACT FROM AUTHOR]

Lymphocytes from patients after bone marrow transplantation (BMT) are in most cases predominantly of the Leu-2+ (cytotoxic/suppressor) phenotypes and are almost unresponsive to mitogens. In contrast, normal Leu-3+-depleted. Leu-2+-enriched lymphocyte suspensions retain approximately 50% of the mitogenic response compared with that of unseparated cells. To investigate whether this discrepancy was due to active suppression, we selected nine BMT patients from whom sufficient numbers of cells were available and whose lymphocyte phenotypes were predominantly Leu-2+ after BMT. These post-BMT lymphocytes were tested for functional suppressor activities against donor and recipient pre-BMT lymphocytes in the lymphocyte transformation test. None of these post-BMT cells suppressed the response of donor or pre-BMT cells to phytohaemagglutinin A or concanavalin A. In contrast, the response of donor cells in mixed lymphocyte cultures to HLA-DR-different third-party cells was suppressed by highly X-irradiated post-BMT cells by approximately 40%. Addition of T-cell growth factor (=interleukin 2 (IL-2)) or X-irradiated donor cells to post-BMT lymphocytes partially restored the mitogenic response. These findings indicate that the early post-BMT cells lack production of IL-2 but are capable of responding to IL-2 and that the almost extinct mitogen response of these cells is due to immaturity rather than active suppression. The suppression of the allogeneic but not the mitogenic response might be explained by differences in the modes of activation; for example, the allogeneic response must involve the T-cell receptor, while the mitogenic response may not. [ABSTRACT FROM AUTHOR]

The lymphocyte transformation response in vitro to mitogens (phytohaemagglutinin, concanavalin A, and pokeweed mitogen) and antigens (purified protein derivative and tetanus) was studied in three patients with acquired immunodeficiency syndrome (AIDS). three patients with pre-AIDS, and six healthy controls before and after depletion of T4- or T8-positive cells. In controls, T8-depleted lymphocytes responded as well as peripheral blood mononuclear cells (PBMC) when monocytes were added, whereas T4-depleted cells gave about 50% of this response to mitogens and no response at all to antigens. No evidence of suppression was seen when various mixtures of T4- and T8-deplcted cells were made. In particular, there was a virtually linear relationship between the percentage of TX-depleted cells and the response to antigens. The PBMC of all AIDS and pre-AIDS patients had very low or absent responses to mitogens and antigens, and except in one case, this response did not increase after depletion of T8-positive cells (and addition of monocytes), indicating that these patient cells also lack suppressor activity in this assay. However, a significantly increased response to mitogens was seen when the TS-depleted suspensions were adjusted to contain 20,000 T4-positive cells per well, but the response was still significantly lower than that of similar suspensions from controls. Thus, not only are the poor responses of PBMC from AIDS and pre-AIDS patients due to a low concentration of T4-positive cells, but the responsiveness of these cells also seems deficient. Furthermore, T8-positive patient cells also have an impaired responsiveness. Our experiments do not exclude the possibility that the low response is due to a T8-negative suppressor cell, but it seems more likely that both the T4- and the T8-positive cells are deficient and/or that there is a deficiency in accessory cells. These possibilities are currently under study. [ABSTRACT FROM AUTHOR]