MURINE MACROPHAGES LACK EXPRESSION OF THE CR-2-145 (CR-2) AND CR-2-190 (CR-1) GENE-PRODUCTS

Murine macrophages have been described as possessing complement recept ors for C3b and iC3b. These binding activities have been assumed to be due to the presence of the CR1 and CR3 proteins, respectively. The mo use Cr2 gene produces two distinct gene products of approximately 190 000 relative molecular mass (M(r)) (Cr2-190) and 145 000 M(r) (Cr2-145 ). Because of the similarity in size to human complement receptors, th e Cr2-190 protein has been dubbed murine CR1 while the murine Cr2-145 product has been termed murine CR2. In order to define the complement receptor genes expressed by murine macrophages, we investigated the ex pression patterns of Cr2-190, Cr2-145 and another mouse complement rec eptor, Crry, in three different mouse macrophage populations: bane mar row-derived macrophages, thioglycollate-elicited peritoneal macrophage s and the macrophage cell line, J774. Neither of the Cr2 gene transcri pts encoding the Cr2-145 and Cr2-190 proteins could be detected in the se populations by RT-RPCR analysis although Crry transcripts were evid ent. Cr2-145 and Cr2s-190 proteins could not be detected on the surfac e of thioglycollate-elicited macrophages using a monoclonal antibody t hat recognizes both proteins. Thus, contrary to previously published d ata, murine macrophages do not possess the Cr2 gene products.