T cell polarization is the process by which naïve CD4⁺ T cells, upon stimulation by signals such as those from antigen-presenting cells and specific cytokines, differentiate directionally into functionally distinct effector subsets like Th1, Th2, Th17, and Treg cells. Each subset secretes characteristic cytokines, mediating cellular immunity, humoral immunity, inflammatory responses, and immune suppression, respectively. This process represents a core mechanism for the precise regulation of adaptive immunity.