MOUSE CD1 IS MAINLY EXPRESSED ON HEMATOPOIETIC-DERIVED CELLS

The mouse CD1 (mCD1) is a class I-like molecule that is encoded outsid e the MHC. Recent studies demonstrate that mCD1 presents hydrophobic p eptides to CD8(+) T cells and also that it is recognized by a populati on of NK1.1(+) T cells that are thought to play an immunoregulatory ro le because of their ability to secrete IL-4, It has previously been re ported that mCD1 is expressed predominantly by intestinal epithelial c ells, although most NK1.1(+) T cells are located elsewhere, We, theref ore, have generated new mAbs to mCD1 to investigate its tissue distrib ution, The principal site of mCD1 expression in normal mice is an cell s in the hemopoietic series, including constitutive expression on near ly all T and B cells, on macrophages, and on dendritic cells, Other th an bone marrow-derived cells, mCD1 is not widely expressed and is not detectable on great majority of intestinal epithelial cells, The B cel ls, but not the T cells, from beta(2)m-deficient mice can be recognize d by two mCD1 autoreactive T hybridomas. Therefore, although we could not detect a beta(2)m-independent form of mCD1 using these mAbs, mCD1 in a different conformation or a mCD1-related molecule is likely to he expressed in the absence of beta(2)m on some cell types. The pattern of expression of mCD1 correlates with the distribution of NK1 T cells and is consistent with an important Ag-presenting function for this mo lecule.