In Vitro Differentiation of Effector CD4⁺ T Helper Cell Subsets

CD4⁺ T "helper" cells are key orchestrators of adaptive immune responses. Upon activation, naïve CD4⁺ T cells are capable of differentiating into a number of effector subsets that perform distinct immune functions. These subsets include T helper 1 (T_H1), T_H2, T_H9, T_H17, T_H22, T follicular helper (T_FH), and regulatory T cell (T_REG) populations. The differentiation of these subsets is dependent, in large part, on the coordinated interplay between signals from the extracellular cytokine environment and downstream transcriptional networks. The use of in vitro T helper cell culture systems has been extensively employed to aid in the elucidation of the molecular mechanisms that govern the differentiation of each effector subset. Here, we provide a detailed summary of the differentiation conditions that are utilized to generate effector CD4⁺ T cell populations in vitro.