THE DISTRIBUTION OF TM-316-ASSOCIATED SURFACE-ANTIGEN ON POLYMORPHONUCLEAR LEUKOCYTES - AN IMMUNOELECTRON MICROSCOPIC STUDY

It has been established that MoAb TM-316 recognizes an epitope on leuc ocytes and specifically inhibits the chemotactic behavior of leucocyte s. In the present paper, the distribution of this epitope on the cell surface and in intracellular organelles was studied by immunoelectron microscopy. Leucocytes separated from the blood of healthy men and fro m synovial fluid from patients suffering from rheumatoid arthritis wer e used. They were fixed with a mixture containing paraformaldehyde, gl utaraldehyde and picric acid. As the second antibody, goat anti-mouse IgM conjugated to 10 nm gold colloids was employed. In normal specimen s, the epitope was found to some extent on the cytoplasmic membrane of neutrophilic leucocytes, but it was only sparsely distributed on eosi nophilic and basophilic leucocytes. On activated neutrophilic leucocyt es, obtained from the synovial fluid of rheumatoid arthritis patients, the immunolabeling was markedly increased. The number of sites where the epitope occurs on the surface of leucocytes is thus associated wit h the cell type, and also with the level of activation of the leucocyt es. In order to investigate the processing of the antigen, the intrace llular localization of the epitope in the neutrophilic leucocytes was also studied. The epitope recognized by TM-316 was also detected in/on the characteristic granules and Golgi stacks.