The generation of lymphokine-activated killer (LAK) activity and the proliferative response to human recombinant interleukin-2 (IL-2) were significantly reduced by the presence of human recombinant leukocyte interferon (IFN alpha) in cultures of human peripheral blood mononuclear cells (PBMC). Mature natural killer (NK) cells can be depleted from PBMC with the toxic lysosomotropic agent L-leucine methyl ester. The generation of cytotoxic cells from lymphocytes depleted in leucine methyl ester was also inhibited by indicating that the IFN-alpha effect is not limited to mature cytotoxic NK cells. Depletion of adherent cells from PBMC did not affect the suppression of LAK induction by IFN-alpha. Surface marker analyses of Tac antigen and transferrin receptor (TfR) showed that the presence of IFN alpha throughout the culture period significantly suppressed the typical increase in IL-2-induced Tac- and TfR-positive cells. In contrast, IFN alpha treatment before and after IL-2 culture enhanced LAK cytotoxic activity. Therefore, combinations of these biological response modifiers for clinical use should take into account the dual effect of IFN alpha on key features of the IL-2 response.
Summary Interleukin 4 (IL-4) suppresses the interleukin 2 (IL-2) induced lymphokine-activated killer (LAK) cell development from human peripheral blood mononuclear cells (PBMC). Suppression is observed at high (1,000 U ml-') as well as low (10 U ml-') concentrations of IL-2. IL-4 needs to be present at the beginning of the IL-2 culture to exert the suppressive effect. IL-4 also inhibits the development of CD25 (Tac) antigen on the PBMC cultured in IL-2. Interleukin I (IL-1) can reverse the suppressive effect of IL-4 on LAK induction when added at the early phase of the IL-2 culture. IL-I enhances IL-2 induced LAK development, which may partially explain the reversion of IL-4 inhibition by IL-1. IL-1 also reverses the inhibitory effect of IL-4 on the development of CD25 antigen expression, although IL-1 alone does not enhance the induction of CD25 expression in PBMC cultured by IL-2. Furthermore, IL-4 suppresses IL-2 induced IL-1 production in PBMC. Thus, suppression of CD25 may be a pathway for the suppression of LAK induction. The expression of CD56 is not directly associated with the expression of LAK activity. IL-4, IL-1 or combination of the two cytokines has no effect on IL-2 induced expression of CD56. These results indicate that IL-4 has an antagonistic effect and IL-1 has a synergistic effect on IL-2-induced LAK development.Interleukin 4 (IL-4) has pleiotropic regulatory effects on components of immune system including resting B cells, macrophages, mast cells, thymocytes (Gause et al., 1988) and peripheral T cells (Brown et al., 1988;Kern et al., 1988). Murine IL-4 can induce lymphokine activated killer (LAK) function (Mule et al., 1987;Peace et al., 1988) and also acts synergistically with interleukin 2 (IL-2) in LAK development (Mule et al., 1989 al., 1988).Recently, it has been shown that IL-4 inhibits the secretion of interleukin 1 (IL-1) from macrophages (Essner et al., 1989), and IL-1 has been reported to promote IL-2 dependent LAK development (Crump et al., 1989). Therefore, we sought to define the manner in which IL-4 can suppress IL-2 induced LAK induction, and to determine if IL-1 can reverse the IL-4 mediated suppression of LAK induction. To approach these questions, we examined the effect these cytokines on modulation of cytotoxicity and on the expression of IL-2 activation markers such as CD25 (Tac) and CD56 (NKH1). Materials and methods Cell preparation and tymphocyte culture
By using rabbit antiserum to a glycolipid, ganglio-n-tetraosylceramide (ASGM1), the accessory effect of natural killer (NK) cells on the generation of alloimmune CTL in mice was investigated. When normal C3H/He mice were immunized with C57BL/6 or BALB/c spleen cells, they generated alloimmune CTL with a surface marker phenotype of Thy-1+ Lyt-1-2+ ASGM1-, preceded by early augmentation of cytotoxic activity of NK cells with a Thy-1-Lyt-1-2-ASGM1+ phenotype. Administration of anti-ASGM1 (10 microliters) in mice resulted in a complete depletion of NK activity and ASGM1+ cells in the spleen even 1 day after injection, but no changes in the proportions of T (Thy-1+) cells and their Lyt-1 and Lyt-2 subsets as revealed by an immunofluorescence analyzer (FACS) and phagocytic cells. When these anti-ASGM1-treated mice were immunized with allogeneic cells, they showed neither augmented NK activity nor generation of alloimmune CTL, and spleen cells isolated from these anti-ASGM1-treated mice produced no CTL response to alloimmunization in vitro. Normal spleen cells treated with the antiserum and complement in vitro also showed a complete NK depletion without any deterioration of T cells and their Lyt-1 and Lyt-2 subsets, and when stimulated with allogeneic cells they generated no CTL. Spleen NK (ASGM1+) cells were purified by Percoll-gradient centrifugations followed by complement-dependent killing of T cells with the use of anti-Thy-1 monoclonal antibody, and were further purified by panning methods with anti-ASGM1, giving a preparation consisting of greater than 90% ASGM1+, Ly-5+ cells, and less than 0.5% of Thy-1+, Lyt-1+, and Lyt-2+ cells. These purified ASGM1+ Thy-1- cells alone generated no alloimmune CTL in response to alloantigens, suggesting that ASGM1+ NK cells contained no precursors of alloimmune CTL. When added into NK-depleted spleen cells, they restored the normal alloimmune CTL response of the spleen cells, indicating that ASGM1+ fractions contained cells to provide an accessory function for CTL generation. Lyt-1+ cells purified by panning methods did not restore the CTL response of NK-depleted spleen cells. These results indicate that ASGM1+ NK cells, but not Lyt-1+ helper T cells contaminating ASGM1+ fractions at undetectable levels, are responsible for the accessory function. When these purified ASGM1+ Thy-1- cells were stimulated with allogeneic cells, they produced IL 2 and IFN.(ABSTRACT TRUNCATED AT 400 WORDS)
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