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.