Profiles of lymphokine activities and helper function for IgE in human T cell clones

Abstract A large panel of phytohemagglutinin (PHA)‐induced T cell clones (690 in total), established from four different human lymphoid tissues (peripheral blood, tonsils, lymph nodes and spleens) by a high‐efficiency cloning technique, was characterized according to their pattern of lymphokine production. The majority of both CD4+ and CD8+clones from all lymphoid tissues produced interleukin (IL) 2 and/or interferon (1FN)‐γ response to 24‐h stimulation with PHA. In contrast, higher proportions of IL4‐producing clones were found among CD4+clones from tonsils and spleens than from peripheral blood and lymph nodes, whereas only a minority of CD8+ clones from all lymphoid tissues were found to produce IL4. It was not possible to divide the CD4+ (helper/inducer) clones on the basis of their pattern of lymphokine activity into two clear‐cut groups analogous to Thl and Th2 helper clones described in mice. Although 21 out of 503 (4%) CD4+ T cell clones produced IL4, but not IFN‐γ or IL2, and 208 (41%) produced IL2 and/or IFN‐γ, but not IL4, a total number of 185 (37%) CD4+ clones showed the ability to produce IL4 plus IL2 and/or IFN‐γ. All types of CD4+ T cells (as classified according to their pattern of lymphokine activity) provided help for IgG production in allogeneic B cells. In contrast, helper function for IgE was detectable only among the IL4‐producing clones. However, the proportion of CD4+ clones providing help for IgE synthesis was significantly lower among those producing IL4 and IFN‐γ or IL4, IL2 and IFN‐γ than among those producing IL4 alone or IL4 and IL2. Thus, a clear‐cut dichotomy between IL4‐ and IFN‐γ‐producing Th cells, as found in mice, does not seem to exist in humans. However, IL4 and IFN‐γ, even if not always produced by distinct T cell subsets, appear to regulate reciprocally the synthesis of IgE in humans as well.