Maturation-dependent expression and function of the CD49d integrin on monocyte-derived human dendritic cells

Dendritic cells (DC) are highly specialized APC that are critical for the initiation of T cell-dependent immune responses. DC exert a sentinel function while immature and, after activation by inflammatory stimuli or infectious agents, mature and migrate into lymphoid organs to prime T cells. We have analyzed integrin expression on monocyte-derived DC (MDDC) and found that expression of CD49d integrins (CD49d/CD29 and CD49d/beta7) was induced/up-regulated during TNF-alpha- or LPS-initiated MDDC maturation, reflecting the induction/up-regulation of CD49d and beta7 mRNA. CD49d mRNA steady-state level increased more than 10 times during maturation, with the highest levels observed 24 h after TNF-alpha treatment. CD49d integrin expression conferred mature MDDC with an elevated capacity to adhere to the CS-1 fragment of fibronectin, and also mediated transendothelial migration of mature MDDC. Up-regulation of CD49d integrin expression closely paralleled that of the mature DC marker CD83. CD49d integrin expression was dependent on cell maturation, as its induction was abrogated by N:-acetylcysteine, which inhibits NF-kappaB activation and the functional and phenotypic maturation of MDDC. Moreover, CD49d integrin up-regulation and MDDC maturation were prevented by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase, but were almost unaffected by the mitogen-activated protein/extracellular signal-related kinase kinase 1/2 inhibitor PD98059. Our results support the existence of a link between functional and phenotypic maturation of MDDC and CD49d integrin expression, thus establishing CD49d as a maturation marker for MDDC. The differential expression of CD49d on immature and mature MDDC might contribute to their distinct motility capabilities and mediate mature DC migration into lymphoid organs.