Separation of normal mature bone marrow plasma cells

Light chain restriction analysis of bone marrow plasma cells in patients with MGUS or 'solitary' plasmacytoma: diagnostic value and correlation with clinical course

Twenty-eight patients with a diagnosis of 'solitary' plasmacytoma or with gammopathy but with nondiagnostic morphologic examination of the bone marrow were investigated using a short-term bone marrow culture technique which enriched for the plasma cell fraction. The percentage of monotypic plasma cells in these plasma cell enriched cultures was correlated with the subsequent clinical course. The majority of patients with plasmacytoma and a significant number of those with gammopathy but with otherwise non-diagnostic investigations were found to have a monoclonal plasma cell component of greater than 20%. There was a significant correlation between the percentage of monoclonal plasma cells as detected by bone marrow culture and subsequent progression to disseminated myeloma. These results indicate that early bone marrow involvement can be detected by means of plasma cell culture prior to morphologic identification of marrow plasmacytosis and that short-term plasma cell culture distinguishes patients with early, low bulk myeloma from those with monoclonal gammopathy of uncertain significance (MGUS).

Endothelial cell receptors on leukemic plasma cells

The binding of peripheral blood mononuclear cells of 7 patients with plasma cell leukemia to rat lymph node high endothelial venules has been studied in vitro. The mononuclear cells adhered selectively to the high endothelial venules. Their neoplastic origin was proved by in situ demonstration of their monoclonal cytoplasmic immunoglobulins. The in vitro binding of bone marrow mononuclear cells of 4 patients with multiple myeloma to high endothelial venules was also studied. In two patients there was no high endothelial cell binding. In the two others some adhering cells were observed. The plasmacytoid nature of these cells was, however, excluded for lack of cytoplasmic immunoglobulins. Since cells at the end stage of B-cell differentiation lose their surface receptors associated with lymphocyte recirculation, the presence of endothelium-recognizing structures on leukemic plasma cells seems to be remarkable.

Quantitation of the monoclonal plasma cell component in bone marrow from patients with serum paraproteinemia and nondiagnostic marrow morphology

Twenty-one patients with serum monoclonal gammopathy but lacking acceptable morphological evidence of myelomatosis were studied with reference to the degree, if any, of monoclonal plasma cell expansion in aspirated marrow samples, enriched for plasma cells and analysed with respect to light chain distribution. Four of these patients had a biopsy-proven plasmacytoma of bone. Bone marrow aspirated from sites distant to the tumor showed clear evidence of infiltration by monoclonal plasma cells in two of the cases studied; the other two patients had normal results. Of the 17 other cases, 14 showed evidence of a monoclonal plasma cell component qualitatively concordant with the serum paraprotein as one would expect. These cases could be subdivided into those with myeloma (six cases) and those with monoclonal gammopathy of undetermined significance (eight cases) on the basis of conventional biochemical and radiological criteria. Three of the 17 patients, however, did not show evidence of monoclonal plasma cell infiltration, despite the presence of lytic lesions. It is important to recognize this minority group that simulates myeloma but that may well reflect alternative pathology that has not been identified.

Characterization of bone marrow stromal cells in suspension and monolayer cultures

Aspirated marrow fragments from healthy adult baboons were cultured in a simple liquid suspension tissue culture system. During the incubation period, haemopoietic cells were discharged from the fragments and settled to the floor of the culture vessels, thus allowing a separation of marrow stromal elements, retained within the fragments. Cells associated with the marrow stroma in vitro were of four main types: adipocytes, macrophages, plasma cells and unidentified lipid-laden cells related to fibroblasts. These last cells were capable of DNA synthesis in vitro, and were morphologically and functionally distinguishable from typical marrow macrophages. Macrophages were characterized by their phagocytic properties. Plasma cells were capable of prolonged survival and immunoglobulin output in vitrol. In monolayer cultures of disaggregated fragment cell suspensions, the lipid-laden stromal cells rapidly assumed fibroblast-like morphology. Fibroblastic proliferation to confluent monolayers was seen within a few days. Plasma cells reorientated themselves around these cells to form rosettes, and bridge communicatons between the two cell types were seen frequently. Plasma cell immunoglobulin output rate per cell appeared to be potentiated by this association.