Expression of Plasma Cell-Associated Non-Light Chain Antigens in Patients with Plasma Cell Dyscrasia and Amyloidosis

Abstract

In this study, we examined reactivity of the plasma cell-reactive monoclonal antibodies MM4 and PCA-1 with bone marrow and other tissue biopsies from patients with documented amyloidosis. Thirty-six biopsies (bone marrow, GI tract, gall bladder, rectum, peripheral nerve, heart, lung, kidney, liver, spleen, tongue, skin, muscle, and adrenal gland) from 17 patients were evaluated independently by standard histopathology. The presence of tissue amyloid was established by the finding of green birefrigence under polarized light after Congo red staining and/or characteristic fibrillar structure by electron microscopy. Cases studied included 13 patients with plasma cell dyscrasia (PCD) and 4 patients without evidence of an M-protein (non-PCD). Reactivity with MM4 or PCA-1 was established by the immunoperoxidase technique, based on comparison with a negative control (no primary monoclonal antibody) section from the same biopsy. MM4 and PCA-1 reacted with marrow plasma cells from the majority of these amyloid patients. In addition, a number of solid organ biopsies demonstrated positive staining with MMA or both monoclonal antibodies in areas of tissue amyloid deposits. Reactivity of either antibody with plasma cells and/or tissue amyloid was independent of light chain isotype. These observations suggest that plasma cells from patients with amyloidosis commonly express MM4-and PCA-1-reactive antigens, which also may be detected in certain tissue amyloid deposits. Further studies with these or similar reagents may help in understanding the pathogenesis of immunocytic amyloidosis.