The antigen is differentially induced in in vitro derived macrophages depending on the colony-stimulating factor applied (IL3 > M-CSF > GM-CSF). Distinct macrophage subpopulations of lymphoid organs express the antigen that reacts with this antibody. In the spleen, they are localized at the marginal sinus forming a ring around the periarteriolar lymphocyte sheath and follicular areas at the inner side of marginal zones. In lymph nodes, they are localized in the sinusoids and medullary cords, but not within follicular areas or paracortex. In Peyer’s patches they are localized in the interfollicular areas at the serosal side. Kupffer cells in the liver can be clearly stained. No reactive macrophages were found in the thymus, brain, kidney, liver, skin or heart. In non-lymphoid organs, the antigen is only found on a macrophage subpopulation in the lamina propria of the villi of the small intestine.

Monoclonal antibody MOMA-1 is a useful marker for the identification of macrophage subpopulations in various organs, mostly characterized by a high level of non-specific esterase expression. Staining is particularly noteworthy with the metallophilic macrophages adjacent to the marginal zone of the spleen. MOMA-1 is also very suitable for differentiation of non-metallophilic marginal zone macrophages as detected by the monoclonal antibody ER-TR9 (ab51819). In addition, MOMA-1 detects macrophages at inflammatory sites and is positive with Kupffer cells.