Effector T-Helper Cell Subtypes

| Home | | Pharmaceutical Microbiology | | Pharmaceutical Microbiology |

Chapter: Pharmaceutical Microbiology : Immunology

Following maturation in the thymus, mature but naive CD4+ helper T-cells access the systemic blood and lymphatic circulations. In this naive state they have yet to be stimulated by antigen.


EFFECTOR T-HELPER CELL SUBTYPES


Following maturation in the thymus, mature but naive CD4+ helper T-cells access the systemic blood and lymphatic circulations. In this naive state they have yet to be stimulated by antigen. The antigen-driven activation signals involve initially TCR interactions with MHC presented peptide and subsequent CD3 activation. This is followed by the interaction of a variety of costimulatory molecules on the surface of the APC (e.g. CD80, CD86) with surface receptors (e.g. CD28) on the helper T-cell. Once the helper T-cell is activated it can proliferate in an autocrine or paracrine fashion driven by secreted IL-2. These proliferating helper T-cells will then differentiate depending on their cytokine environment; for example, IFN-γ and IL-12 drive the differentiation to a TH1 subpopulation of cells while IL-4 drives the differentiation to a TH2 subpopulation of cells.

Apart from IL-2 the main cytokines produced by TH1 cells are IFNγ and TNFβ, and the main cell partner for TH1 cells are the APCs. The TH1 cells classically promote cell-mediated immune responses maximizing the effectiveness of APCs and the proliferation of cytotoxic CD8+ T-cells. Apart from IL-2 the main cytokines produced by TH2 cells are IL-4, 5,6,10 and 13, while the main cell partner for TH2 cells is the B-cell. The TH2 cells classically promote the humoral immune responses stimulating B-cells to proliferate to undergo Ig class switching and increase Ig production and secretion.

The above model of helper T-cell subpopulations and how various cytokines can serve to promote the differentiation pathway to either TH1 or TH2 phenotype is recognized to be an oversimplification. However, the basic model serves to emphasize that distinct populations of helper T-cells exist that fulfil many different and varied functions.

Contact Us, Privacy Policy, Terms and Compliant, DMCA Policy and Compliant

TH 2019 - 2022 pharmacy180.com; Developed by Therithal info.