Comparison of CD1 monoclonal antibodies on bovine cells and tissues

A comparison was made of six mAbs within temporary clusters TC19 and TC28 that were previously established, or considered from unpublished data, as recognizing bovine and ovine CD1. All six immunoprecipitated a molecule of 46 kDa from iodinated thymocytes together with a second molecule of 12 kDa that appeared to be beta 2 microglobulin. mAb 20-27 (Workshop code 038) recognized a molecule expressed on bovine monocytes and B cells from bovine peripheral blood as well as thymocytes and cells with a dendritic morphology in sections. mAb CC20 (033) was shown to stain COS cells transfected with human CD1b cDNA and this mAb together with CC14 (not in workshop panel) and CC90 (007), which gave identical staining by flow cytometry and immunohistology, should all be regarded as being bovine CD1b mAb. The bovine CD1b molecule is expressed on bovine thymocytes and a proportion of cells with a dendritic morphology in tissue sections. Flow cytometric data with mAbs CC40 (039) and CC122 (043) were not sufficiently similar to data with mAb CC20 to allow the two mAbs to be regarded as CD1b although they did appear to be directed against bovine CD1 molecules. Furthermore, CC122 recognized a molecule expressed by a high proportion of cells in the lamina propria of the gut that was not recognized by the other mAbs. The findings indicate that the six mAbs recognize at least two and possibly four CD1 antigens.