FIGURE 1 Adaptive T cell activation and subsets. Adaptive T-cell effects induce CD4 and CD8 expression through thymocyte expansion. The T cell receptor (TCR) is activated by the recognition of complexes formed by CD8 and major histocompatibility complex (MHC) class I and CD4 and MHC class II on antigen-presenting cells (APC). In CD4+T cells, help T (Th)1, Th17, Th22, Th2, and regulatory T cell (Treg) release respectively proinflammatory and anti-inflammatory cytokines to participate in the immune process.