Heterogeneity of CD4+ and CD8+ T cells

There is extensive plasticity in the T-cell response to antigen. Helper CD4+ T cells, cytotoxic CD8+ T cells, the progression from naïve to effector and memory T cells, and differentiation into Th1, Tc1, Th2 and Tc2 subsets have long been recognized. More recently it has become apparent that T-cell populations display additional diversity in terms of phenotype, anatomical distribution and effector function.