Analysis of the distribution and function of rat CD1 molecule

The MHC class I-like molecule CD1 has been recently identified as a new antigen presenting molecule that is distinct from MHC class I and MHC class II molecules. We have previously cloned and identified the rat homologue of CD1. In this report, we examined tissue distribution of rat CD1 by the use of an anti-rat CD1 antibody. Rat CD1 was expressed on the surfaces of lymphoid cells, mainly thymocytes and spleen cells, as well as non-lymphoid cells including hepatocytes and intestinal epithelial cells. The pattern of distribution generally accorded with that of mRNA. We also found that certain subpopulations of T cells recognized CD1. These cells showed cytotoxic and proliferative responses against CD1 positive cells. Thus, the results suggest that CD1 molecules play significant roles in the immune system, probably in the development of lymphoid cells and antigen presentation.