title: Restricted production of interleukin 4 by activated human T cells.
abstract: Interleukin 4 (IL-4) is secreted by activated T cells and pleiotropically modulates both B- and T-lymphocyte function. In murine helper (CD4+) T-cell clones IL-4 production appears to be regulated independently of interferon gamma and interleukin 2. To determine whether production of these lymphokines is also differentially regulated in uncloned human T cells, we studied lymphokine production by normal human peripheral T cells and T-cell subsets after in vitro polyclonal activation. After maximal induction of lymphokine expression, IL-4 mRNA was detectable in less than 5% of CD4+ and 1-2% of unfractionated T cells, whereas approximately 33% and 60% of CD4+ cells expressed detectable mRNA for interferon gamma and interleukin 2, respectively. This finding correlated with dramatically lower production of IL-4 mRNA and protein than of interferon gamma and interleukin 2 by peripheral blood and tonsillar T cells. The helper-inducer (CD4+ CD45R-) T-cell subset, which significantly enhances in vitro immunoglobulin production, accounted for the preponderance of IL-4 mRNA accumulation and protein production by CD4+ T cells; nevertheless, cells with detectable IL-4 mRNA constituted less than 10% of the CD4+ CD45R- subset. Limitation of IL-4 production to a comparatively small population of normal human T cells could selectively regulate the effects of this lymphokine in T-cell-mediated immune responses; such selective regulation may be a fundamental mechanism for restricting the potentially pleiotropic effects of certain lymphokines to appropriate responder cells.
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D016827:CD8 Antigens; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D015847:Interleukin-4; D007378:Interleukins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D007376:Interleukin-2; D007378:Interleukins; D012333:RNA, Messenger; D015847:Interleukin-4; D007371:Interferon-gamma