Background Increased production of IL-4 and IL-5 and decreased production of IFN-γ by CD4+ T cells has been implicated in asthma pathogenesis. However, CD8+ T cells also produce type 1 and type 2 cytokines and the relative roles of CD4+ and CD8+ T cell cytokine production in asthma have not been previously studied.
Objective To determine the production of the type 1 and type 2 cytokines by CD4+ and CD8+ T cell subsets in asthmatic and normal subjects.
Methods Intracellular cytokine staining for IL-4, -5, -10, -13 and IFN-γ was analysed in peripheral blood CD4+ and CD8+ T cells from 24 atopic asthmatic and 20 normal subjects.
Results Both subsets of T cells produced all cytokines studied and there were no significant differences between CD4+ and CD8+ T cells in their capacity to produce either type 1 or type 2 cytokines. There were significantly increased frequencies of IFN-γ-positive CD4+ (13.1 ± 2.4%, vs. 7.3 ± 1.4%) and CD8+ (20.0 ± 2.9%, vs. 9.6 ± 2.1%) T cells in asthmatic subjects compared with normal subjects (P < 0.05), but not in frequencies of CD4+ or CD8+ T cells staining positively for IL-4, -5, -10 or -13.
Conclusion The frequencies of peripheral blood CD8+ T cells producing type 1 and type 2 cytokines are comparable with the frequencies of CD4+ T cells. There was an increased frequency of IFN-γ producing CD4+ and CD8+ T cells in asthmatic compared with normal subjects. Further studies investigating T cells derived from the airways and investigating various stages within the disease process are required to further elucidate the importance of type 2 and type 1 T cell cytokine production in the pathogenesis of human allergic disease.