Allergen-stimulated interleukin-4 and interferon-gamma production in primary culture: responses of subjects with allergic rhinitis and normal controls.

The balance of interleukin-4 (IL-4) to interferon-gamma (IFN-gamma) production that is induced following exposure to common environmental antigens is believed to be instrumental in determining whether hypersensitivity or clinical unresponsiveness results to that antigen. To date, evaluation of cytokine (protein) production has been based predominantly on allergen-reactive CD4 T-cell clones or activation of fresh unselected peripheral blood mononuclear cell (PBMC) populations with non-physiological stimuli such as phorbal myristate acetate (PMA) and calcium ionophore, phytohaemagglutinin (PHA), anti-CD3 or anti-CD2/anti-CD28 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 from grass pollen-sensitive allergic rhinitis subjects and non-atopic controls were stimulated using a range of grass pollen allergen concentrations in the absence of exogenous cytokines or polyclonal activators. The majority of subjects (45 of 52) exhibited chloroquine-sensitive, CD4-dependent cytokine production in allergen-stimulated, short-term primary culture. Median IL-4 production was substantially greater among atopics (13.0 pg/ml versus < 1 pg/ml, Mann-Whitney U test, P < 0.0000001) 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 from normal and atopic donors was underscored by examination of the ratios of IFN-gamma:IL-4 synthesis. Non-atopic individuals exhibited intense IFN-gamma dominance of the T-cell response, in marked contrast to that 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 antigen stimulation in vitro argues that the most relevant consideration in determining susceptibility to immediate hypersensitivity versus clinical tolerance to environmental allergens is not a genetically defined capacity to recognize the antigen (i.e. if allergen-reactive T cells are present in that individual) but the nature of the cytokine response.