AbstractThe cytokine secretion profiles of T cell lines (TCL) specific for purified proteinderivative (PPD) or streptokinase (SK), contemporarily derived from nine atopic and nine nonatopic individuals, were compared. Upon stimulation with phorbol myristate acetate(PMA) plus anti‐CD3 monoclonal antibody (mAb), all TCL from both atopics and nonatopics produced interleukin (IL)‐2 and interferon (IFN)‐γ. The mean IL‐2 production by PPD‐ or SK‐specific TCL from both atopics andnonatopics was similar, whereas the mean IFN‐γ production by TCL derived from atopics was significantly lower. In addition, both PPD‐ and SK‐specific TCL from atopics produced detectable amounts of IL‐4 and IL‐5, whereasthe corresponding TCL derived from nonatopics did not.A total number of 107 and 99 PPD‐specific CD4+T cell clones (TCC)were then derived from TCL of 4 atopic and 4 nonatopic donors and assessed for their profile of cytokine production in response to stimulation with either PMA plus anti‐CD3 mAb or the specific antigen. Under both these experimental conditions, virtually all PPD‐specific TCC from both atopic and nonatopic individuals produced IL‐2 and IFN‐γ. In contrast, the great majority of PPD‐specific TCCderived from nonatopic individuals did not produce IL‐4 and IL‐5, whereashigh proportions of PPD‐specific TCC derived from atopic donors displayed the ability to produce noticeable amounts of IL‐4 and IL‐5 besides IL‐2 and IFN‐γ.These data indicate that CD4+T cells from atopic individuals are able toproduce IL‐4 and IL‐5 in response to bacterial antigens, such as PPDand SK, that usually evoke responses with a restricted type‐1 T helper (Th1)‐like cytokine profile in nonatopic individuals. Aberrant IL‐4 production by Thcells may represent one of the immune alterations resp
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