Adaptive immunity can be split into two major parts: cell-mediated immunity driven by T cells and humoral immunity, which is dominated by antibodies and also involves T cells. T cells are developed in the thymus and circulate in the bloodstream and the lymphatic system until they contact antigen and differentiate into effector T cells. Antigens from ingested bacteria or toxins and pathogens that multiply in intracellular vesicles are presented to the cell surface by MHC-class II proteins for binding with CD4+T cells1. The T cell receptor-mediated binding of the MHC-presented antigen, as well as other co-stimulatory binding events and protein signaling, determine the differentiation pathway taken by the now activated T cells1.

Interleukin (IL)-2 is required for activation and clonal expansion2. In activation there are a number of differentiation pathways that can be taken by the T cells, distinguished by the cytokines that the cells release3. TH1 requires interferon-γ, IL-12 alongside IL-23, and IL-18. Interferon-γ is produced by stimulated T cells and by natural killer cells and is the major product of the TH1 cells. IL-12 is generally produced by neighboring macrophages and dendritic cells. The TH2 response requires IL-4, with a threshold of IL-4 being able to override the presence of IL-12 and interferon-γ3. The major cytokines produced by TH2 cells include IL-4, IL-5, IL-9, and IL-134. The TH17 response is induced by the presence of TGFβ, IL-6, IL-1β, and IL-23 in mice and IL-23, IL-1β, TGF-β, IL-6 in humans5. Interferon-γ produced by TH1 cells activates macrophages to enhance microbiocidal activity, induces antibody class switching to IgG that fixes complement, and triggers cytokine production that results in cytotoxic T cell production and inhibits the production of TH2 cells3. The TH2 response leads to the production of IgG that does not activate complement and to the production of IgE, the Ig class involved in the development of allergy3. The TH17 response assists in and might be required for the TH1 response5.

Quansys has multiple cytokine kits for examining T cell differentiation. Contact us to learn more.

References

1. Janeway C, Travers P: Immunobiology : the immune system in health and disease. London; San Francisco; New York: Current Biology Limited; Garland Pub. Inc.; 1994.
2. Virella G: Medical immunology. 5th edn. New York: M. Dekker; 2001.
3. Kindt TJ, Goldsby RA, Osborne BA, Kuby J: Kuby immunology. 6th edn. New York: W.H. Freeman; 2007.
4. Barnes PJ: Th2 cytokines and asthma: an introduction. Respir Res 2001, 2:64-65.
5. Khader SA, Gopal R: IL-17 in protective immunity to intracellular pathogens. Virulence, 1:423-427.