Selective inhibition of antigen‐induced “step one” in cytotoxic T lymphocytes by anti‐Lyt‐2 antibodies

Abstract

Stimulation of mixed lymphocyte cultures with ultraviolet (UV)-irradiated stimulator cells leads to selective activation of Lyt-2+ cytotoxic T lymphocyte precursors (CTL-P) to acquire interleukin 2 (IL2) reactivity: (a) no proliferative response, nor IL2 production was observed in these cultures; (b) upon addition of preformed IL2-conditioned media (IL2-CM), a vigorous proliferative response was observed; (c) the IL2-dependent proliferation was reduced by approximately 90% after depletion of Lyt-2+ responder cells; and (d) specific CTL were generated upon the initial triggering by UV-irradiated stimulators and IL2 expansion. This system therefore provides suitable conditions for studying the role of Lyt-2 antigens in initial, antigen-specific induction of CTL-P, as well as at their effector phase. It is shown herein that monoclonal anti-Lyt-2 antibodies inhibit antigen-specific acquisition of IL2 reactivity by CTL-P, which results in 85% reduction of the proliferative response mediated by IL2-CM. CTL-P which have been induced by antigen to IL2 reactivity, prior to addition of anti-Lyt-2 antibodies, however, are not affected in their IL2-dependent proliferation. Furthermore, both the specific and lectin-dependent cytolytic activity of effector CTL generated by UV-irradiated stimulators and IL2-CM is blocked by addition of anti-Lyt-2 antibodies in the cytotoxicity assay. The implications of these findings for the role of Lyt-2 antigen in antigen recognition by T cells are discussed.

Detection of Cell‐Mediated Lympholysis Determinants Encoded by the I‐A and I‐E Genes on Ultraviolet‐Irradiated Spleen Cells

“…The same authors [5] also studied the effects of IL-1 on the generation of CTLs in UV MLR. In contrast to what has previously been described in Gullberg & Larsson [6], they could correct the U V irradiation-induced defect of antigen presentation with purified preparations of IL-1. The discrepancy can be explained by the fact that the dose of UV light they used was not sufficient to abrogate totally the response, since a good level of lysis was obtained in the absence of any added soluble factor and the only effect of the addition of IL-1 was an increase of the cytolytic activity generated.…”

“…It is reasonable to assume that, when using suboptimal doses of UV light, a residual helper cell-stimulating activity is left in the stimulator cell population, which would be facilitated by the addition of IL-1. In contrast, in experiments in which UV light treatment totally abrogated the response, addition of IL-1 was not sufficient to restore the response [6]. Using the same doses and irradiation protocol as Gullberg & Larsson, we did not observe cytotoxic activity in the absence of conditioned medium (see Table I), although class II determinants were effectively presented in CTL precursors.…”

“…The latter point is particularly important because T helper cells and CTL behave differently in this regard. Gullberg & Larsson [6] reported the failure to reconstitute a proliferative response to fully allogeneic UV-irradiated cells by the addition of a partially purified preparation of IL-1. Thus, no IL-2 production could be obtained even in the presence of an exogenous source of T helper cell 'differentiation' factors.…”

On the role of I‐A antigens in lectin‐ and antigen‐induced interleukin 2 production

“…Antigen-induced IL 2 production was obtained by incubating a cloned Th cell line (2 X 105/ml) characterized elsewhere [13, 141 with anti-Thy-1.2-and C-treated, irradiated (2000 rds), PC (1 x 106/ml) for 24 h. When indicated, mAb were added at initiation of culture. IL2 activity was assayed by titrating the various IL 2-rich supernatants on ILZreactive T cell blasts from BALBlc (H-2d) mice (1 X lo5/ ml) and the IL2 activity quantified as previously described [15]. The results are expressed as percent I L 2 activity as compared to the respective control supernatants obtained after induction without mAb.…”

A Combination of Soluble Helper Factors Bypasses the Requirement for Stimulator Cells and Induces Nonspecific Cytotoxic T Cell Responses

“…Production of IL 1 (5) and subsequently of IL 2 (4,6) are essential for the antigen-independent proliferation of IL 2 reactive Lyt-2 + CTL precursor cells (7). IL 2 reactivity has been shown to be induced by a short exposure to specific ligands including allo-H-2 antigens (8).…”