Monoclonal antibodies with selective reactivity against osteoblasts and osteocytes in human bone

Monoclonal antibodies (MAb) may provide valuable tools for studying osteoblast differentiation. We therefore raised a panel of MAb reactive with cells of this phenotype using 1,25(OH)2D3-treated human trabecular osteoblast-like cells (HOBS) as the immunogen. Immunohistochemical studies on various tissues, including undecalcified cryostat sections of fetal and adult human bone, identified 11 bone cell-reactive MAb. Of these, 2 demonstrated particularly selective reactivities against osteocytes (OB/M) and osteoblasts (OB/L). These reactivities were also seen in developing bone from rat, rabbit, and marmoset. OB/L and OB/M demonstrated limited reactivity against a small number of human tissues from the extensive panel of substrates tested. Both MAb exhibited reactivity against discrete populations of cells in the large and small intestine. In addition, OB/L reacted with cells in the basal epidermis of skin and OB/M with cells in blood vessel walls. Both antibodies demonstrated reactivity against a variety of cultured osteoblast-like cell lines and other cultured cell types. These MAb may therefore provide a valuable means of studying osteoblast ontogeny.