Characterization of Mouse CD4 TCR and Its Targeting Antigen

The initial step of activation and differentiation of naïve CD4⁺ T cells is the TCR-antigenic stimulation. The specific antigen peptides (>11 residues) are presented by the class II MHC (MHC II) protein which expresses professional antigen-presenting cells (APCs). To recognize various peptides and highly polymorphic MHC molecules, a diverse TCR repertoire is achieved through random V(D)J rearrangement. Following TCR initiation, naive CD4⁺ T cells proliferate and differentiate into one of the lineages of T helper (Th) cells, including Th1, Th2, Th17, iTreg, and some new subsets, as defined by the signatures of functional cytokines. In this chapter, we provide a series of methods to identify antigens for a specific TCR in vitro and also track the dynamics of the specific TCR-expressing T cell in vivo.