Antigen-specific, I-A-restricted suppressor hybridomas with spontaneous cytolytic activity. Functional properties and lack of rearrangement of the T cell receptor beta chain genes

Regulatory interactions among autologous T cell clones. Human bifunctional T cell clones regulate the activity of an autologous T cell clone

In contrast to the ease of cloning and characterizing, at the molecular level, helper and cytotoxic T cells, suppressor T cells remain an enigma, and their existence as discrete entities is being increasingly challenged. Here we review evidence that CD4+ regulatory clones, capable of expressing both helper and suppressor functions, may account for much of the suppressor function. It is suggested that a single T cell clone, depending on the signals it receives from its environment, may release either helper or suppressor cytokines. Studying such clones under defined conditions (providing suppressor signals), may preclude detection of their helper capacity. Since some therapeutic approaches in various human diseases are based on the manipulation of helper and suppressor functions, the question whether committed suppressor cells exist has important practical implications in medicine.

Phenotypic and functional characterization of human suppressor T-cell clones: II. Activation by Mycobacterium leprae presented by HLA-DR molecules to alpha beta T-cell receptors

We have been studying human T-cell clones that suppress anti-mycobacterial T-cell responses but not T-cell responses to an unrelated antigen or mitogen. In the present paper we report our studies on the activation requirements of these suppressor-T-cell clones. The suppressor-T-cell clones could proliferate and produce interferon-gamma upon stimulation with Mycobacterium leprae and other mycobacteria but not with unrelated antigens or autologous T cells. Both suppressor and nonsuppressor clones react to a 36-kDa antigen of M. leprae. Thus far, we have not been able to demonstrate whether they see the same or different epitopes. The antigen-driven proliferation of suppressor-T-cell clones was, however, significantly lower than that observed for T-cell clones that did not mediate suppression. The proliferation of suppressor-T-cell clones to M. leprae antigens could be blocked by monoclonal antibodies to HLA-DR, alpha beta T-cell receptor, interleukin-2 receptor, and, in the case of CD4-positive suppressor-T-cell clones, anti-CD4 monoclonal antibodies. DR restriction of the antigen presentation to these suppressor-T-cell clones was shown in mixing experiments using antigen-presenting cells as mononuclear cells from family members and unrelated individuals. These experiments also indicated that apart from regular DR-restriction a hitherto unknown factor may be required for presentation to or activation of suppressor-T-cell clones that is present in the family members and unrelated individuals with the same ethnic and geographic background but absent in DR/Dw-matched healthy Dutch individuals.

T-cell clone anti-clone interactions. Effects on suppressor and helper activities

An experimental model of two interacting clones of T cells is described, which may be used for defining and exploring the T-cell immunoregulatory network. Mx9/9 is a CD4 clone bearing an antigen receptor recognized by the Mx9 anti-V beta 8 monoclonal antibody (MoAb). Anti-V beta 8 MoAbs activate and induce cell proliferation of this clone. Autologous clones were raised against Mx9/9 cells using the peripheral blood mononuclear (PBM) cells of the Mx9/9 clone donor (PBMjm). Some of these cloned anti-clone cells proliferated after stimulation with irradiated Mx9/9 cells, but not after stimulation with other autologous cloned T cells or heterologous PBM, suggesting that these clones recognize the T cell receptor (TCR) of the Mx9/9 cells. The proliferation of the Mx9/9 stimulated cloned anticlone cells was blocked by anti-class II MoAbs, indicating that the autoreactive clones recognize their target antigen in conjunction with HLA Class II products. The ability of clone Mx9/9 to proliferate after stimulation with anti-V beta 8 MoAb was inhibited when clone 121 cells were added to the cultures. However, clone 121 lost its suppressor function after 4 months in culture and instead gained the ability to enhance the proliferation of Mx9/9 cells in the presence of anti-V beta 8 MoAb. In contrast, clone 18 lacked suppressor activity at the early stage of the study but later acquired this function. We conclude that some autoreactive clones are not fully committed and may express more than a single function. Such cells cannot therefore be designated as 'suppressor cells', although they expressed suppressor potential at certain stages.

T-cell receptors of human suppressor cells

Cells which can suppress the immune response to an antigen (TS cells) appear to be essential for regulation of the immune system. But the characterization of the TS lineage has not been extensive and many are sceptical of studies using uncloned or hybrid T-cell lines. The nature of the antigen receptor on these cells is unclear. T cells of the helper or cytotoxic lineages appear to recognize their targets using the T-cell receptor (TCR) alpha beta-CD3 complex. TCR beta-gene rearrangements are also found in some murine and human suppressor cell lines but others have been shown not to rearrange or express the beta-chain or alpha-chain genes. We previously established TS clones derived from lepromatous leprosy patients which carry the CD8 antigen and recognize antigen in the context of the major histocompatibility complex (MHC) class II molecules in vitro. We here report the characterization of additional MHC-restricted TS clones which rearrange TCR beta genes, express messenger RNA for the alpha and beta chains of the TCR and express clonally unique CD3-associated TCR alpha beta structures on their cell surface but do not express the gamma chain of the gamma delta TCR on the cell surface. We conclude that antigen recognition by at least some human CD8+ suppressor cells is likely to be mediated by TCR alpha beta heterodimers.

Identification of a putative second T-cell receptor

Framework monoclonal antibodies have identified a population of human lymphocytes that express the T3 glycoprotein but not the T-cell receptor (TCR) alpha- and beta-subunits. Chemical crosslinking experiments reveal that these lymphocytes express novel T3-associated polypeptides, one of which appears to be the product of the T gamma gene. The other polypeptide may represent a fourth TCR subunit, designated T delta.