Allergen‐induced cytokine phenotypes in mice: role of CD4+ and CD8+ T cell populations

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Abstract
Summary: Background CD4+ T cells expressing type 2 cytokines have been implicated in the pathogenesis of asthma to high‐molecular‐weight allergens. Topical exposure of BALB/c strain mice to low‐molecular‐weight chemical contact and respiratory allergens stimulates type 1 and type 2 cytokine secretion phenotypes, respectively.Objective To examine the relative frequencies of cytokine‐positive CD4+ and CD8+ T cells and their contributions to these cytokine secretion profiles.Methods Draining auricular lymph nodes were isolated 13 days after initiation of topical exposure of female BALB/c strain mice to chemical allergen, or to vehicle alone. The frequency of intracellular cytokine (IL‐4 and IFN‐γ)‐positive CD4+ and CD8+ lymphocytes was enumerated by flow cytometry. The relative contribution of CD4+ and CD8+ cells to cytokine secretion profiles was assessed by negative selection.Results Exposure to allergen resulted in an increased frequency of both IFN‐γ+ CD4+ and CD8+ lymphocytes, although there were no marked differences between trimellitic anhydride (TMA)‐ and 2,4‐dinitrochlorobenzene (DNCB)‐activated lymph node cells. Treatment with TMA induced approximately five times as many IL‐4+ CD4+ cells as did exposure to DNCB. This pattern of cytokine staining was also observed for a further pair of contact and respiratory allergens; respectively, formalin and fluorescein isothiocyanate.Conclusion These data demonstrate that the divergent immune responses induced in mice by different classes of chemical allergen are independent of changes in the frequency of IFN‐γ+ cells, but are associated with differential frequencies of IL‐4‐expressing CD4+ T cells.

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