Inverse relationship between dendritic cell CCR9 expression and maturation state.

CCR9 has been identified on T cells as a chemokine receptor that directs these cells to migrate to the intestine. CCR9 has also been reported on different cell types in the intestine, thymus, liver and peripheral blood. Little is reported concerning the presence of or functional implications of this chemokine receptor on myeloid dendritic cells (DC). In the host, DC encounter a multiplicity of antigenic stimuli to which they mount immune responses. In addition to intracellular and functional changes on sensing antigen, maturation of DC is typically reflected in the up-regulation of costimulatory molecules on DC. However, alterations in other surface markers may also be an indicator of DC activation. Using bone marrow-propagated DC these studies investigated cellular maturation in the presence of microbial stimuli and analyzed the relationship of CCR9 expression with DC maturation. Fractionation of DC into CCR9(high) and CCR9(low)subsets revealed a distinct ability of each subset to induce division in naïve CD4(+) T cells. Our results suggest that DC expressing high levels of CCR9 are less activated/mature than DC expressing low levels of CCR9.