ANTIGEN-MEDIATED AND POLYCLONAL STIMULATION OF HUMAN CYTOKINE PRODUCTION ELICIT QUALITATIVELY DIFFERENT PATTERNS OF CYTOKINE GENE-EXPRESSION

Polyclonal activators are widely used as surrogate antigens in analysis of human cytokine gene expression. An implicit assumption is that the T cell activation and cytokine production observed in response to polyclonal activation provides a more intense, but qualitatively identical, reflection of results that would be obtained with antigen. Here we demonstrate that stimulation using accessory cell independent (immobilized anti-CD3 mAb) or dependent [phytohemagglutinin (PHA) or soluble anti-CD3 mAb] polyclonal activators yields different conclusions from those that are obtained in response to antigen-specific T cell activation. Cytokine synthesis in 1-5 day bulk cultures of fresh peripheral blood mononuclear cells (PBMC) from 52 subjects evenly divided between grass pollen sensitive allergic rhinitis subjects and normal, non-atopic controls were examined. Antigen-specific re-stimulation elicited elevated IL-4 and IL-10 production and lower IFN-gamma synthesis among allergic subjects than normal non-atopic control subjects. This commitment of fresh PBMC towards a T(h)2-like response in atopics and the dominance of the IFN-gamma response seen in non-allergic subjects was reinforced when the ratio of IFN-gamma:IL-4 production in bulk culture was examined. Atopic individuals exhibited median IFN-gamma:IL-4 values of 0.07, whereas grass pollen stimulated cytokine production by normal subjects yielded a ratio of 4.8. In marked contrast, IL-2, IL-4, IL-10 and IFN-gamma production elicited using polyclonal activators, though much more intense, did not differ between allergic and non-allergic subjects (Wilcoxon rank sum test P>> 0.05), Anti-CD3 mediated stimulation evoked ratios characteristic of T(h)1-dominant responses in both populations (IFN-gamma:IL-4 ratios of 10 and 14), while PHA elicited T(h)2 dominant responses (ratios of 0.40 and 0.22) in both normal and allergic subjects. The data indicate the importance of using specific activation signals in characterizing T cell responses.