Thymic and Postthymic Regulation of Naïve CD4⁺ T-Cell Lineage Fates in Humans and Mice Models

Figure 2

Schematic representation of the cytokines and transcription factors controlling CD4⁺ T-cell differentiation. Upon antigenic stimulation by antigen-presenting cells, naïve CD4⁺ T-cells (Tho) expand and differentiate into at least seven effector cell subsets. Each of these phenotypes is induced by a signature pattern of cytokines (pink box) and multiple transcription factors (blue, nucleus) and regulated by distinct cytokines (yellow box). Some cytokines promote the clonal expansion of naïve antigen-specific T-cells and the acquisition of T-cell effector functions whereas others such as TGF-β, IL-6, IL-9, IL-17, IL-22, and IL-23 avoid redifferentiation and conversion of Treg cells into Th1/Th17 pathogenic phenotype. The phenotypic plasticity that drives conversion of some Th-subtypes to another Th-type is a mechanism not yet fully understood.