Subsets of T-helper lymphocytes , involved in cell-mediated immune responses.

TH1 cells secrete IL-1 and gamma interferon , which enhance cell-mediated responses and inhibit both TH2 subset cell activity and the humoral immune responses. TH1 is inflammatory , produces IL2, IFNgamma, TNFbeta, provides help to B-cells in IgG2a production, activates macrophages and CTL and stimulates delayed type hypersensitivities.

TH2 cells, the other subset of T-helper cells, are also involved in cell-mediated immune responses. TH2 cell activity and secretions are thought to inhibit cell-mediated responses and to enhance the humoral response. TH2 cells produce IL4 , IL5, IL6, IL10 and IL13, which provide help to B cells and induce class switch to IgE and IgG1 , as well as supporting eosinophils and mast cells .