Temporal regulation of IL-12p70 and IL-12-related cytokines in splenic DC subsets during Leishmania donovani infection

Immunology and Infection Unit, Hull York Medical School and Dept. of Biology, University of York, Wentworth Way, York YO10 5YW U.K.

^* To whom correspondence should be addressed. Email: pmk2{at}york.ac.uk.

	Abstract

DC play an essential role in initiating and directing T-cell responses, in part by production of IL-12p70, IL-23 and IL-27. However, comparative studies on the capacity for cytokine production of DC subsets are rare. Here, we compare splenic CD8⁺, CD4⁺ and double negative (DN) DC, isolated 5h-28d after Leishmania donovani infection, for i) production of IL-12p70, ii) accumulation of IL-12/23p40, IL-12p35, IL-23p19 and IL-27p28 mRNAs and iii) their capacity to direct CD4⁺ T cell differentiation. At 5h, cDC accumulated mRNA for IL-12/23p40 (CD8>CD4>DN), IL-23p19 (CD4>CD8>DN) and IL-27p28 (CD8>CD4>DN), in an infection dose-dependent manner. IL-12p70 was restricted to CD8⁺ cDC, reflecting the subset-specific accumulation of IL-12p35 mRNA. In contrast, cDC from mice infected for 14-28d accumulated little mRNA for IL-12p40 and IL-12p19, though IL-27p28 mRNA remained detectable (CD8>DN>CD4). IL-12p70 secretion by CD8⁺ cDC was also absent, reflecting deficient IL-12/23p40, rather than IL-12p35, mRNA accumulation. The capacity of CD8⁺ isolated early after infection to direct Th1 cell differentiation was mediated through IL-12/23p40, whereas this ability in CD4⁺ and DN cDC was independent of IL-12/23p40 and did not result from over-expression of Delta 4 notch-like ligand. However, DN cDC produced IFN and also contained a rare population of CD11c^hiDX5⁺ IFN-producing cells. Our data illustrate the extensive diversity in, and temporal regulation of, splenic cDC subsets during infection, and suggests caution in interpreting data obtained with unfractionated or minimally purified DC.