ABSTRACT
Selective recruitment of lymphocyte populations to the skin and other tissues is a crucial element of both immune surveillance and immune response to specifi c stimuli. Dysregulation of leukocyte recruitment plays a key role in the pathogenesis of various skin diseases, including infl ammatory disorders such as atopic dermatitis or psoriasis, and in the evasion of immune defenses by malignancies, such as squamous cell carcinoma and melanoma. Leukocyte homing depends on the stepwise interaction of blood cells in fl ow with the vascular wall. Each step in this cascade is necessary, but not suffi cient, to direct recruitment and retention of individual cells at a defi ned site of interest. Together they provide specifi city of site and selectivity in leukocytes recruited, as well as protection against inappropriate accumulation of eff ector leukocytes. Th erapeutic strategies targeting key molecules in the recruitment paradigm have proved eff ective and promise to provide even more options for tissue-and/or cell-selective manipulation of leukocyte homing. In this chapter, we discuss the current model of tissue-specifi c leukocyte recruitment, focusing on skin, and the role of adhesion receptors in regulating primary and memory immune responses.
