These activated B-1 B cells are then able to produce antigen-specific IgM antibodies in vivo [10]. We note that stimulatory lipids may not be entirely unique to post-sensitization livers, as the response induced by iNKT cell stimulation with lipids from livers of naïve mice was greater than the baseline response (Groups E versus B, Fig. 1A,B). Thus, there may be a background level of iNKT cell stimulation by endogenous lipids, which is consistent with prior descriptions of partially activated iNKT cells

in naïve mice. Alternatively, this observation may represent iNKT cell activation from background exposure to microbial components such as cell wall glycosylceramides. Potential activation by the murine microbiota would not detract from the results, however, as the same degree of enhancement would be seen GSK126 in all

experimental groups. Adoptive transfer of LMNC from wild-type mice can reconstitute CS in CD1d-deficient mice. We show that CD1d itself is essential, based on experiments involving anti-CD1d-blocking antibody. However, background BGJ398 in vivo expression of CD1d in recipient mice is not necessary for CS reconstitution. We conclude that the transferred iNKT cells are sufficiently activated in vitro. By extension, LMNC are inferred to be presenting lipid antigen via CD1d, thereby activating iNKT cells. Candidate APC include hepatic dendritic cells [31] and iNKT cells themselves [32]. Although hepatocytes seem well suited to serve as essential APC for the presentation of lipid antigens to iNKT cells, our results suggest that they are not essential. APC amongst LMNC are sufficient. Following adoptive transfer, activated donor iNKT cells do not home to the recipient liver at 1 day yet are able to reconstitute CS. We performed

this experiment in Jα18−/− and CD1d−/− mice, both strains of which are iNKT cell deficient, with the same result. Hepatocytes in Jα18−/− mice express CD1d, but this potential to present glycolipids to iNKT cells did not appear to lure donor iNKT cells. Reconstituted CS therefore appears to represent a slightly different phenomenon than wild-type CS, despite phenotypic similarities. We conclude that extrahepatic activation of iNKT cells occurs in reconstituted mice, an important consideration Adenosine in the future utilization of this mouse model for understanding iNKT cell biology. Despite these revelatory data, we still contend that the liver is an essential site for iNKT cell activity, based on our prior work. We have previously shown that actively sensitized mice double their percentage of hepatic iNKT cells (as measured by tetramer binding) within 2 h after sensitization, likely a reflection of both an increase in numbers and activation [9]. We have shown in wild-type mice that very early after sensitization, hepatic iNKT cells express IL-4 and not IFN-γ [10].