Involvement of "accessory" and antigen receptor molecules in human helper T cell clone activation studied by monoclonal antibody inhibition

Differential role of lymphocyte function-associated antigens in the activation of nickel-specific peripheral blood T lymphocytes

The possible role(s) of the adhesion molecules LFA-1 alpha (CD11a), LFA-1 beta(CD18), ICAM-1 (CD54), CD2 (T11, LFA-2), and LFA-3 (CD58) in the in vitro activation of nickel-specific peripheral blood (PB) T lymphocytes was studied. For this purpose, monoclonal antibodies (MoAb) to these markers were used. Both LFA-2 and LFA-3 appeared to be consistently involved, whereas LFA-1 was inconsistently involved. In studies using antigen-presenting cells (APC) isolated from peripheral blood to present nickel, anti-LFA-1 alpha and/or LFA-1 beta MoAb partially inhibited the in vitro activation of nickel-specific T lymphocytes in nine of 42 patients allergic to nickel. In the other 33 patients variable results, ranging from a slight increase or inhibition of proliferation to no inhibition at all, was observed, in particular when different anti-LFA-1 alpha MoAb were added to the cultures. In those patients who showed no inhibition when anti-LFA-1 (alpha and beta) MoAb were added, no inhibition was also observed when a mixture of anti-LFA-1 (alpha and beta) and ICAM-1 MoAb were added to the cultures. Similar results were also obtained using epidermal APC. In control experiments the various anti-LFA-1 (alpha and beta) MoAb effectively inhibited the tetanus toxoid and Con-A induced T-lymphocyte proliferation as well as the spontaneous aggregation of the JY cell line. Anti-CD2 and anti-LFA-3 MoAb strongly inhibited the proliferative responses of nickel-specific peripheral blood T lymphocytes from all 42 patients. These results indicated that the receptor-ligand interaction between CD2 and LFA-3 is essential for in vitro activation of nickel-specific peripheral blood T lymphocytes. This activation, however, does not regularly involve LFA-1 molecules on T lymphocytes. The involvement of LFA-1 in the activation of nickel-specific T lymphocytes correlated positively with high patch test scores to nickel and the disease activity in contact dermatitis patients.

Monoclonal antibodies to CD6 preferentially stimulate T-cell clones with gamma/delta rather than alpha/beta antigen receptors

CD6 is a pan-T-cell structure about which very little is known, although certain CD6 monoclonal antibodies have been reported to be mitogenic for T cells. Using a heterogeneous collection of human T-cell clones, we now show that CD6-responders were contained exclusively within the gamma/delta-receptor+ group. Three of seven CD6 antibodies tested stimulated autocrine proliferation of 5 of 7 gamma/delta but 0 of 13 alpha/beta T-cell clones. Stimulation was dependent on the presence of accessory cells, which could not be substituted by interleukin 1 beta or 6. These results suggest that a subset of human T cells carrying gamma/delta antigen receptors may be selectively stimulated by the as yet unknown CD6 ligand.