Terminal maturation of human macrophages is an important step for creation of cell diversity amongst site-specific subpopulations and their functional competence in situ. As monocytes undergo differentiation in vitro, they start to express lineage-restricted antigens specific for differentiation stages beyond the blood monocyte level as detected by monoclonal antibodies of the MAX series. We have analyzed the expression of MAX.1, MAX.2, MAX.3 and MAX.11 on exudate-type macrophages from pleural and peritoneal cavity and the alveolar space, as well as on resident and activated tissue macrophages in cryostat sections of spleen, lymph node, tonsil, liver, gut mucosa, skin, placenta, kidney and bone. It was found that "free" macrophages in serous cavities expressed MAX antigens in a heterogenous pattern, whereas none of the organ-specific tissue macrophages subsets did so (with the exception being the weak label of MAX.2 on Kupffer cells). Only during allograft rejection were infiltrating macrophages found to express MAX antigens but not at sites of "non-specific" inflammation or granuloma formation. However, Cyclosporin A treatment seems to suppress the induction of MAX antigen expression on intragraft macrophages. In addition, freshly harvested MAX-negative exudate macrophages converted to the complete Max+ phenotype on further cultivation. Isolated Kupffer cells were able only to express the MAX.2 antigen in culture but still did not react with the MAX.1 and MAX.3 monoclonal antibodies. Some MAX antigens are co-expressed on glomerular mesangial cells, dendritic reticulum cells and placental cells (MAX.1/.11) as well as on capillary endothelium within tissues of active immune response (MAX.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Summary.A mouse monoclonal antibody raised against acute myeloid leukaemia cells (YB5.B8 monoclonal antibody; Gadd. S, J. and Ashman, L, K, (1985): Leukaemia Res. 9, 1329-1336) ha,s been found by an indirect immunoperoxidase lechnique to bind lo scattered cells in frozen sections from a number of buman tissues. They have been identified as mast cells in fixed sections of skin, tonsil and duodenum by simultaneous staining of glycosaminoglycan wilh Alcian blue in 0.7 N HCl, The antibody does not distinguish mast cells in mucosal tissues from Ihose in conneclive tissue, altbough ihe level of expression by cells al both sites appears to be heterogeneous. Wilh tbe exception of tow affinity binding lo B lymphocytes, no other bone marrow-derived cells were found to bind the antibody. In particular, basophils and eosinophils were not stained, suggesting that they are not related closely to masi cells and that the antigen detected by YB5.B8 monoclonal aniibody is not an IgE Fc receptor. Therefore, among all mature haemopoieiic lineages, the antibody is specific for mast cells.

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