Phagocyte-dependent host responses

Phagocyte-dependent host responses are partially controlled by Th1 cells, whereas phagocyte-independent immune responses are controlled by Th2 cells. Specifically, Th1 cells promote the production of opsonizing and complement-fixing antibodies, macrophage activation, antibody-dependent cell cytotoxicity, and delayed-type hypersensitivity. Th2 cells primarily provide help for humoral immune responses such as IgE- and IgG1-isotype switching and mucosal immunity.

Th2 cells also provide signals that induce mast cell and eosinophil growth and differentiation and facilitate IgA synthesis. Moreover, some Th2-derived cytokines (such as IL-4, IL-10, and IL-13) inhibit certain macrophage functions. Recently, two activation markers have been identified that are associated with the two primary subsets of T helper cells. Lymphocyte activation gene-3 (LAG-3) is an activation marker associated with Th1 cells and is a member of the immunoglobulin superfamily. CD30 is an activation marker associated with Th2 cells, and is a member of the TNF receptor family.