Dendritic cells produce macrophage inflammatory protein-1γ, a new member of the CC chemokine family

Langerhans cells (LC) are skin-specific members of the dendritic cell (DC) family. DC are unique among APC for their capacity to activate immunologically naive T cells, but little is known about their chemotactic recruitment of T cells. We now report that LC produce macrophage inflammatory protein-1γ (MIP-1γ), a newly identified CC chemokine. MIP-1γ mRNA was detected in epidermal cells freshly procured from BALB/c mice, and depletion of I-A⁺ epidermal cells (i.e., LC) abrogated that expression. MIP-1γ mRNA was detected in the XS52 LC-like DC line as well as by 4F7⁺ splenic DC and granulocyte-macrophage CSF-propagated bone marrow DC. XS52 DC culture supernatants contained 9 and 10.5 kDa immunoreactivities with anti-MIP-1γ Abs. We observed in Boyden chamber assays that 1) XS52 DC supernatant (added to the lower chambers) induced significant migration by splenic T cells; 2) this migration was blocked by the addition of anti-MIP-1γ in the lower chambers or by rMIP-1γ in the upper chambers; and 3) comparable migration occurred in both CD4⁺ and CD8⁺ T cells and in both activated and nonactivated T cells. We conclude that mouse DC (including LC) have the capacity to elaborate the novel CC chemokine MIP-1γ, suggesting the active participation of DC in recruiting T cells before activation.