Functional subsets of allergen-reactive human CD4+ T cells.

After a period of resistance, the concept of human helper T (TH)-cell subsets is gaining currency. This is the result of analyses from a number of laboratories on the cytokine profiles of T-cell clones prepared from chronically-infected and hypersensitive individuals. Here, Martien Kapsenberg and colleagues summarize these studies and speculate on the significance of skewed TH1 and TH2 responses.