Human Types I and 2 T Helper Subsets: Functional Properties, Role in Disease and Regulation of Development

Abstract

In recent years it has become clear that the type of an antigen-specific immune response is determined by the selective or preferential activation of CD4⁺ T cell subsets secreting defined patterns of cytokines that lead to strikingly different T cell functions. Two very distinct cytokine secretion patterns were initially defined among a panel of mouse CD4⁺ T cell clones (Mosmann et al. 1986). Thelper type 1 (T_H1), but not T helper type 2 (T_H2), cells produce interleukin (IL)-2, interferon-γ (IFN-γ) and lymphotoxin (LT), whereas T_H2, but not T_H1, cells express IL-4, IL-5, IL-6 and IL-10. Other cytokines are produced by both T cell subpopulations (Mosmann et al. 1986; Mosmann and Moore 1991). More recent data on the cytokine secretion patterns of T cell clones and normal T cells have revealed the existence of other phenotypes. Among mouse clones, a pattern of IL-2, IL-4, IL-5 and IFN-γ (T_H0) has been described (Street et al. 1990), and in some cases these clones have been shown to produce all cytokines tested, including IL-3, IL-10 and granulocyte-macrophage colony-stimulating factor (GM-CSF; Mosmann and Moore 1991).