Sequential maturation stages of monoclonal B lineage cells from blood, spleen, lymph node, and bone marrow from a terminal myeloma patient.

In order to fully understand the complexity of the monoclonal B lineage cells in multiple myeloma, it is necessary to evaluate the extent to which these cells are resident in solid lymphoid tissues and the phenotypic differences and similarities as compared to the circulating or bone marrow derived B lineage cells. Peripheral blood mononuclear cells from a patient with multiple myeloma were obtained 8 and 3 days prior to death, and mononuclear cells from lymph nodes, spleen, and bone marrow were obtained at autopsy. Rapid changes in the stage of differentiation of blood late-stage B lineage cells towards mature end-stage plasma cells were observed during the last week prior to death. Lymphoid cells within the blood comprised very few T cells, sub-normal numbers of monocytes, and 80% of B lineage cells which were at a late stage of differentiation. Shortly before death, plasma cells were found in the peripheral blood, indicating progression to plasma cell leukemia. At autopsy, the monoclonal B lineage cells in lymph node, spleen, and bone marrow represented different stages of terminal B cell differentiation. In each tissue, the B lineage cells were at an earlier differentiation stage, as defined phenotypically, than the circulating B lineage cells found in blood 3 days prior to death. Analysis of B cell markers and CD45 was used to define the differentiation stage of the relevant B cell populations, revealing a series of differentiation stages. The least mature B lineage cells (CD45hi) were found in lymph node. However, the CD45 isoform expressed was CD45R0, unlike most normal lymph node B cells. More differentiated B lineage cells (CD45med) were found in the bone marrow, and three sequential stages of pre-plasma cells were found in the spleen (CD45bright, CD45moderate, and CD45low-neg), all of which were CD45R0+. The B cells in normal spleen and bone marrow are CD45RA+. The presence of monoclonal B lineage cells in spleen was confirmed by Southern blotting. The B lineage cells from peripheral blood 3 days prior to death were approaching an end-stage plasma cell stage (CD45low/-). On B lineage cells from the various myeloma tissues, a concomitant loss of CD11b and increasing density of CD29 were observed as a function of progression to terminally differentiated stages.