Enhancement of human allogeneic cytotoxic responses by interferons

Interleukin-2 activated human killer lymphocytes: lack of involvement of interferon in the development of IL-2-activated killer lymphocytes

When cultured with native or recombinant interleukin-2 (IL-2) human small agranular lymphocytes acquire the ability to kill various tumor targets. The development of these IL-2 activated killer (IAK) cells, also known as LAK, is observed in the absence of antigen or mitogen. Interferons are known to augment the lytic effects of natural killer cells and cytolytic T lymphocytes. Our study was undertaken to examine the effect of human alpha, beta, and gamma interferons on the induction and the effector phase of IAK function. When cultured with small lymphoid cells IFN alone did not induce anti-tumor cytolytic activity in those lymphocytes. Despite their known anti-proliferative effects, none of the 3 IFN species at any concentrations tested inhibited the development of IAK activity when present during the entire culture period. IFN neither inhibited nor augmented the development of IAK cells under suboptimal conditions. Furthermore, activation of IAK cells was not affected by the presence of neutralizing antibodies to either alpha or gamma IFN. Post-activation exposure of IAK cells to IFN also failed to either augment or inhibit their lytic activity. Thus, neither endogenously generated nor exogenously added IFN had any effect on the IAK system, in contrast to their augmenting effects on NK cells and CTL.

Selective up-regulation by interferon-gamma of surface molecules of the Ly-6 complex in resting T cells: the Ly-6A/E and TAP antigens are preferentially enhanced

Surface molecules encoded by the murine Ly-6 locus can transduce triggering signals in T cells and thus may play important roles in T cell function. Previously, we found that Ly-6 molecules are up-regulated by interferon (IFN)-alpha/beta in resting T cells. Here, we examined the possible influence of IFN-gamma on these molecules. Purified T cells from C57BL/6 (Ly-6.2) and BALB/c (Ly-6.1) mice were incubated in vitro with recombinant murine IFN-gamma and the expression of Ly-6 antigens was measured by flow cytofluorometry. It was found that both Ly-6A/E and T cell-activating protein (TAP) molecules are markedly enhanced while Ly-6C is less affected. Under the same conditions, other T cell surface molecules showed no or marginal changes. The effect of IFN-gamma on Ly-6A/E and TAP expression reached a maximum with as little as 10 U/ml and required only 18-24 h of incubation. Moreover, the enhancement of Ly-6A expression induced by IFN-gamma was stable for at least 5 days. Analysis of T cell subsets further revealed that IFN-gamma-induced augmentation of Ly-6A (C57BL/6 mice) involves both Lyt-2+ and L3T4+ cells while the increase of Ly-6E (BALB/c mice) is more pronounced in Lyt-2+ cells. The functional consequence of these phenotypic alterations was evaluated by studying the mitogenic responses of T cells to antibody-mediated Ly-6 cross-linking in the presence of phorbol myristate acetate. Pretreatment of resting T cells with IFN-gamma dramatically increased the responses to anti-Ly-6A and anti-Ly-6E monoclonal antibodies. IFN-gamma treatment also boosted the stimulation induced by anti-TAP monoclonal antibody when this stimulation was performed under suboptimal conditions. Therefore, IFN-gamma selectively up-regulates the Ly-6A/E and TAP activation pathways in resting T cells. We speculate that this effect may contribute to the immunoregulatory activities of IFN-gamma.