Immunochemical studies on bone marrow of the rat.

A water soluble extract of rat bone marrow was compared with similar extracts of several other organs of the reticuloendothelial system by simple electrophoresis in agar gel and by immunoelectrophoretic analysis followed by selective staining of chemical and enzymatically active constituents. Antiserum prepared against the soluble bone marrow extract showed extensive cross-reactions with extracts of the other organs used in the study; the extracts possessing the most antigenic constituents in common with marrow were those of spleen and peritoneal exudate cells. Immunoelectrophoretic analysis of the marrow extract, combined with absorption of the anti-marrow serum with extracts of the other organs, permitted the identification of the antigens common to marrow, spleen, peritoneal exudate cells, lymph node, thymus, liver and heart. Every antigen detected in bone marrow was found in at least one other organ extract and several of these antigens were found to possess enzymatic activities. Transferrin was the only serum protein identifiable in large amount in extracts of well washed bone marrow cells.