Properties of receptors on macrophages for allogeneic MHCs (H-2D^d and H-2K^d)

Abstract

[Background] We have previously shown that allograft-induced macrophages (AIM) in C57BL/6 (H-2D^bK^b) mice were essential for allograft (e.g., BALB/c skin and Meth A tumor; H-2D^dK^d) rejection. Recently, we reported the isolation of two cDNAs, which encoded novel receptors on AIM for allogeneic MHCs (H-2D^d and H-2K^d), respectively, by using anti-AIM monoclonal antibodies (mAbs; R15 and R12) and allogeneic MHC tetramers (H-2D^d and H-2K^d). We named these two receptors macrophage MHC receptor (MMR) 1 and MMR2, respectively. In the present study, we explored the percentages of MMR1⁺ or MMR2⁺ AIM by staining with R15 or R12 mAb and investigated the homologues of MMR1 and MMR2 proteins in human and other species. [Results] There were no AIM expressing both MMR1 and MMR2. The R15⁺MMR1⁺ and R12⁺MMR2⁺ AIM were ≈76% and ≈8%, respectively. Human homologues of MMR1 (95% homologous) and MMR2 (71% homologous) were found by a search for sequence homology (BLAST http://blast.genome.ad.jp/). Also, the MMR1 and MMR2 protein sequences were considerably conserved in other animal species such as chicken, blowfish, xenopus, C.elegans, zebrafish and drosophila. [Conclusion] Most of AIM expressed H-2D^d receptors, whereas H-2K^d receptor-positive cells were the minor population of AIM. Homologues of MMR1 and MMR2 were seen in human and other animal species, implying that the allorecognition systems by MMR1 and MMR2 on AIM might be conserved among various species of animals. [J Physiol Sci. 2007;57 Suppl:S127]