Chemokine-Driven CD4⁺ T Cell Homing: New Concepts and Recent Advances

CD4⁺ T cells are critical regulators of the adaptive immune system and have diverse roles in regulating responses to the broad array of microbes encountered. Appropriate execution of their effector function requires precise and coordinated migration of these cells to specific lymphoid niches and peripheral sites. This migration is largely controlled by dynamic expression of chemokine receptors and the discrete functions of distinct subsets of CD4⁺ T cells can often be determined from their expression of specific chemokine receptors. In this chapter, we discuss recent advances in the subset-specific homing of distinct T helper populations, focusing on new insights stemming from the increased diversity and plasticity now observed among CD4⁺ T cells as well as how chemokine receptors can govern T cell-fate decisions. We also discuss current understanding of CD4⁺ memory T cells with reference to their diversification based on chemokine receptor expression.