IFN gamma is secreted by

TH1 cells produce the cytokine IFN-g, which activates macrophages in the classical pathway. TH2 cells secrete IL-4, IL-5, and IL-13, which recruit and activate eosinophils and are responsible for the alternative pathway of macrophage activation IFNg, or type II interferon, is a cytokine that is critical for innate and adaptive immunity against viral, some bacterial and protozoal infections. IFNg is an impoant activator of macrophages and inducer of Class II major histocompatibility complex (MHC) molecule expression. Aberrant IFNg expression is associated with a number of autoinflammatory and autoimmune diseases. The impoance of IFNg in the immune system stems in pa from its ability to inhibit viral replication directly, and most impoantly from its immunostimulatory and immunomodulatory effects. IFNg is produced predominantly by natural killer (NK) and natural killer T (NKT) cells as pa of the innate immune response, and by CD4 Th1 and CD8 cytotoxic T lymphocyte (CTL) effector T cells once antigen-specific immunity develops TH17 cells secrete IL-17 and other cytokines that induce the secretion of chemokines responsible for recruiting neutrophils and monocytes into the reaction ref robbins basic pathology 9th ed page 55