Equine macrophage identification with an antibody (Ki-M6) to human CD68 and a new monoclonal antibody (JB10)

Monoclonal antibodies (mAbs) recognizing equine macrophages are scarce. The present study compared the immunocytochemical staining of various equine t issues (lymphoid tissue, lung, liver, small intestine, skin and blood leuco cytes) by an antibody, Ki-M6, which detects CD68 in human macrophages and d endritic cells, and by a new anti-equine mAb, JB10, with staining produced by two previously described anti-equine macrophage mAbs, CZ2.2 and CZ3.3. K i-M6 was shown to identify equine macrophages, which had a distribution dif ferent from those identified by CZ2.2 and CZ3.3. JB10 identified equine mac rophages with a distribution similar to those identified by Ki-M6, but addi tionally bound to polymorphonuclear leucocytes. Flow cytometry of periphera l blood leucocyte subpopulations and tissue immunocytochemistry were used t o compare staining by JB10 with that of CZ2.2 and CVS19; the latter identif ies the myeloid antigen, EqCD13, found on polymorphonuclear leucocytes. The staining by JB10 differed from that of both CZ2.2 and CVS19, suggesting th at JB10 detects a different molecule. These additional mAbs should prove us eful for the future study of new, defined, populations of macrophages in eq uine immune responses and pathology, and, in the case of:Ki-M/6 antibody, m ay make possible an analysis of the structure, distribution and function of the CD68 molecule in the horse. (C) 2000 Harcourt Publishers Ltd.