IMMUNE-MEDIATED INFLAMMATION: HUMAN T CD4 HELPER LYMPHOCYTE DIVERSITY AND PLASTICITY IN HEALTH AND DISEASE

RODOLFO ALBERTO KÖLLIKER FRERS; MATILDE OTERO-LOSADA; MARÍA INÉS HERRERA; SABRINA PORTA; VANESA COSENTINO; EDUARDO KERZBERG; LUCAS UDOVIN; FRANCISCO CAPANI

"Cells of the Immune System"

IntechOpen

Año: 2019; p. 1 - 14

The CD4+ T helper (Th) cells are mature T cells expressing the surface protein CD4 that have a critical role in organizing the adaptive immune response. The emerging cells of the differentiation after the immune synapse produce helper T cell subpopulations that activate, suppress, or regulate the immune response upon interaction with varying immune cells. Two main Th cell categories may be considered regarding their function. The ´effector cells´ protect against exogenous antigens (pathogens or allergens) or can damage endogenous self-antigens under pathogenic conditions, v.g., autoimmune diseases. The ´regulatory T cells´ avoid autoimmune reactions and stop the effector response against exogenous cells.Classic T helper lymphocytes can also be distinguished by their lineage according to the developmental microenvironment, the expression of cell adhesion-homing receptors, the profile of cytokines they are exposed to, and the involved transcription factors. Some of them have not only effector but regulatory properties as well. Traditionally, the CD4+ and the CD8+ phenotypes have been considered as helper and cytotoxic/ suppressor T lymphocytes respectively. Currently, the distinction is little rigorous as there are cytotoxic CD4+ lymphocytes and CD8+ lymphocytes with a secretory profile of cytokines.The immune response is exceedingly complex beyond the classic Th1 and Th2 effector cells´ involvement, and other populations of helper T lymphocytes have been phenotypically characterized. These include the Th17, Tfh (follicular helper T lymphocyte), Th22, and Th9 lymphocytes. Besides contributing to keeping the immune system homeostasis, these helper T lymphocytes, also participate in the pathogenesis of several immune-mediated inflammatory disorders. Notwithstanding their different lineage, the CD4+ T cells have shown phenotypic plasticity. Presumably, the Th17 subpopulation cells are more plastic than was supposed. They maintain the ability to adopt the Th1 or Th2 phenotype and the respective secretory profile of cytokines.