NONSPECIFIC IMMUNOSTAINING OF BLAST CELLS OF ACUTE-LEUKEMIA BY ANTIBODIES AGAINST NONHEMOPOIETIC ANTIGENS

It is well known that some of the widely used antibodies directed agai nst hemopoietic antigens exhibit cross-reactivity with normal and neop lastic nonhemopoietic cells. By contrast, relatively little is known a bout the immunoreactivity of hemopoietic cells with antibodies that de tect nonhemopoietic antigens. In this study 43 routinely processed bon e marrow biopsy specimens containing infiltrates of acute leukemia of different subtypes were stained with a panel of 20 antibodies that det ect nonhemopoietic antigens in formalin-fixed and paraffin-embedded ti ssue. Thirteen of the antibodies applied (KL1; BMA 120; and antibodies against epithelial membrane antigen, alpha-fetoprotein, prostate-spec ific acid phosphatase, prostate-specific epithelial antigen, placental alkaline phosphatase, alpha-amylase, serotonin, bombesin, beta-human chorionic gonadotrophin, desmin, and S-100 protein) did not stain blas t cells in any of the cases. However, anti-vimentin, HMB45, and anti-m yoglobin stained blast cells in the majority of the cases; the antibod ies against thyroglobulin, actin, and carcinoembryonic antigen stained blast cells in 10% to 25% of the cases; and anti-neuron-specific enol ase stained blast cells in less than 10% of the cases. No correlation was found between the leukemia subtype and the pattern of immunoreacti vity. The staining specificity, (i.e., the specificity of binding of t he primary antibody-immunologic vs. nonimmunologic binding), was reste d by increasing the dilution of the primary antibody and comparing the staining intensity in the bone marrow specimens and control tissue. S taining specificity was confirmed only for staining with the antibodie s against neuron-specific enolase and vimentin. The findings show thar immunoreactivity of tumor cells in bone marrow biopsy specimens for n onhemopoietic antigens does not exclude a diagnosis of acute leukemia.