An immunomorphological and immunochemical study was performed to elucidate the pattern of carbohydrate antigens and their relationships to the cluster differentiation (CD) 68 epitopes on macrophages derived from human bone marrow and milk. Core and backbone antigens recognized by lectins from Bauhinia purpurea (BPA), Helix pomatia (HPA), Arachis hypogaea (PNA), Glycine max. (SBA), Griffonia simplicifolia (GSA-I-B4), Lycopersicon esculentum (LEA) and Erythrina cristagalli (ECA) were expressed by both macrophage populations. Additionally, they exhibited various peripheral type 1 and type 2 carbohydrate antigens. In bone marrow trephine biopsies, the number of macrophages stained by the CD68-specific monoclonal antibody PG-M1 exceeded significantly (range 30-40%) the subpopulation expressing SBA, GSA-I-B4, and ECA binding sites as well as the Lewisa antigen. This result is very interesting since, from in vitro studies GSA-I-B4 and SBA are known to react especially with activated macrophages. Western blotting experiments on milk macrophage lysates revealed that ECA, GSA-I-B4, BPA, PNA and MAA visualize a 110 kDa band isographic with the CD68 antigen detected by PG-M1, KP1 and Ki-M1P monoclonal antibodies. These antibodies recognize peptide epitopes as shown by enzyme-linked immunosorbent assays after biochemical modification of milk macrophage lysates. This result is in keeping with the assumption that the CD68 antigen consists of a highly glycosylated mucin-type glycoprotein comprising various differentiation-dependent epitopes.