ALLERGEN-STIMULATED INTERLEUKIN-4 AND INTERFERON-GAMMA PRODUCTION IN PRIMARY CULTURE - RESPONSES OF SUBJECTS WITH ALLERGIC RHINITIS AND NORMAL CONTROLS

The balance of interieukin-4 (IL-4) to interferon-gamma (IFN-gamma) pr oduction that is induced following exposure to common environmental an tigens is believed to be instrumental in determining whether hypersens itivity or clinical unresponsiveness results to that antigen. To date, evaluation of cytokine (protein) production has been based predominat ely on allergen-reactive CD4 T-cell clones or activation of fresh unse lected peripheral blood mononuclear cell (PBMC) populations with non-p hysiological stimuli such as phorbal myristate acetate (PMA) and calci um ionophore, phytohaemagglutinin (PHA), anti-CD3 or anti-CD2/anti-CD2 8 monoclonal antibodies (mAb). Here, ultrasensitive IL-4 and IFN-gamma assays were optimized to allow direct analysis of antigen-stimulated cytokine production by fresh human PBMC. Primary cultures of cells fro m grass pollen-sensitive allergic rhinitis subjects and non-atopic con trols were stimulated using a range of grass pollen allergen concentra tions in the absence of exogenous cytokines or polyclonal activators. The majority of subjects (45 of 52) exhibited chloroquine-sensitive, C D4-dependent cytokine production in allergen-stimulated, short-term pr imary culture. Median IL-4 production was substantially greater among atopics (13.0 pg/ml versus < 1 pg/ml, Mann-Whitney U test, P < 0.00000 1) and IFN-gamma was lower (P = 0.008), providing direct evidence for an imbalance in both IL-4 and IFN-gamma production among circulating, pollen-reactive cells in individuals with seasonal allergic rhinitis. The distinction in the allergen-driven cytokine responses elicited fro m normal and atopic donors was underscored by examination of the ratio s of IFN-gamma:IL-4 synthesis. Non-atopic individuals exhibited intens e IFN-gamma dominance of the T-cell response, in marked contrast to th at observed among grass pollen-sensitive individuals (median IFN-gamma :IL-4 ratios of 14.0 versus 0.096, P = 0.000002). The observation that essentially all individuals produced IFN-gamma (+/-IL-4) following an tigen stimulation in vitro argues that the most relevant consideration in determining susceptibility to immediate hypersensitivity versus cl inical tolerance to environmental allergens is not a genetically defin ed capacity to recognize the antigen (i.e. if allergen-reactive T cell s are present in that individual) but the nature of the cytokine respo nse.