KI-S1 AND PROLIFERATING CELL NUCLEAR ANTIGEN EXPRESSION OF BONE-MARROW MACROPHAGES - IMMUNOHISTOCHEMICAL AND MORPHOMETRIC STUDY INCLUDING REACTIVE (INFLAMMATORY) MYELITIS, SECONDARY APLASTIC-ANEMIA, AIDS, MYELODYSPLASTIC SYNDROMES AND PRIMARY (IDIOPATHIC) OSTEOMYELOFIBROSIS

There is general agreement on the fact that bone marrow macrophages pr esent a non-proliferating cell population. Using a sequential double-i mmunostaining technique, a morphometric analysis was performed on rout inely processed bone marrow biopsies derived from 70 patients. The pur pose of this study was, firstly, to determine the frequency of bone ma rrow macrophages in a variety of lesions and, secondly, to elucidate w hether there is any proliferative activity detectable by immunohistoch emical markers. Bone marrow pathology included reactive myelitis (RM), secondary aplastic anaemia (AP), AIDS-related myelopathy, primary (id iopathic) osteomyelofibrosis (OMF) and myelodysplastic syndromes (MDS) . The monoclonal antibody PG-M1 which recognizes a formalin-resistant epitope on macrophages and PC10 raised against proliferating cell nucl ear antigen (PCNA) were employed. For comparison with the PCNA-labelli ng index, the newly developed monoclonal antibody Ki-S1, which is asso ciated with cell proliferation, was applied. In comparison with normal bone marrow, morphometric evaluation revealed a significant increase in macrophages in MDS, OMF, RM and especially in HIV-infected patients . Moreover, a positive immunostaining of single macrophages with PC10 was noted very infrequently. This rather inconspicuous PCNA labelling increased in AIDS. By contrast, Ki-S1 expression was found in none of the other pathologies studied. The prevalence of the macrophage popula tion in certain disorders may have a multifactorial origin, such as in flammatory changes like intercurrent infections in AIDS and enhanced c ell turnover in MDS as well as involvement of the complex pathomechani sms generating bone marrow fibrosis. In keeping with previous studies, the insignificant PCNA expression of macrophages should not be relate d to cell proliferation, but to unscheduled DNA strand repair which ma y be generated in the course of viral infection in AIDS.