Читать книгу Immunology - Richard Coico - Страница 47

T cell antigen engagement in secondary lymphoid tissues shapes the repertoire of antigen‐specific T cells and defines their functional attributes. In other words, antigen engagement directs the responding T cell towards a specific functional subset which include T_H1, T_H2, T_H17, T_FH, and T_Reg cells. Note that other T_H subsets have also been defined. Differentiation of T_H cells into effector cells is regulated, in part, by exposure of naïve CD4⁺ T cells to certain cytokines as shown in Figure 2.12. However, T_H cell differentiation can be somewhat plastic. What determines subset differentiation is multifactorial and does not only depend on TCR engagement. Dose of antigen can play a role but most importantly, it is the cytokine milieu at the site of priming that is most relevant. There is also controversy regarding the possible plasticity of T‐cell subsets. Evidence suggests that T‐cell differentiation towards a specific functional subset may be subject to change at a later time under different conditions of antigen activation.

Table 2.2 summarizes the surface phenotypes, cytokine profiles, transcription factors, and functional properties of the major T_H cell subsets.