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

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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.

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