Characterization of the monoclonal blood and bone marrow B lymphocytes in Waldenström's macroglobulinaemia

Impact of circulating lymphoma cells at diagnosis on outcomes in patients with Waldenstrom macroglobulinemia

Given the paucity of data surrounding the prognostic relevance of circulating lymphoma (CL) in Waldenström macroglobulinemia (WM), we sought to evaluate the impact of CL at diagnosis on outcomes in patients with WM. Patients were divided into CL+ and CL- based on the results of flow cytometry. The endpoints included assessing progression-free survival (PFS), overall survival (OS), and diagnosis-to-treatment interval (DTI) between the two groups. Among the 308 patients with WM, 69 met the eligibility criteria with 42 and 27 in CL+ and CL- groups, respectively. The two groups were well balanced in regard to all the baseline characteristics. The ORR was numerically higher in the CL+ group compared to the CL-group (81% versus 61%, respectively), however, the CR+VGPR rates were similar between the two groups. The median PFS was not significantly different between the two groups (6.3 years in the CL- group versus not reached [NR] in the CL+ group) regardless of the first-line therapy. There was no significant difference in median OS between the CL- and CL+ groups (13 years versus NR). Although the median DTI was shorter in the CL+ group compared to CL- group, the significance was lost in the multivariable analysis. In this study (largest-to-date) evaluating the impact of CL on outcomes in patients with newly diagnosed WM, we did not find the prognostic utility of CL in WM. Future studies should explore the correlation of CL with other biological factors that impact the outcomes in WM patients.

Transitions in CD45 isoform expression indicate continuous differentiation of a monoclonal CD5+ CD11b+ B lineage in Waldenstrom's macroglobulinemia

Waldenstrom's macroglobulinemia (WM) has been hypothesized to be a pleomorphic B-cell malignancy with persistent maturation towards plasma cells in all lymphoid tissue. This proposal is based on detection of a heterogeneous density of monoclonal Ig on peripheral blood B-cells in patients with WM. We now present data derived from 2- and 3-color immunofluorescence and flow cytometric analysis that strongly supports this hypothesis. Abnormally high numbers of B lineage cells, defined by expression of CD19, CD20, and CD24, were found among peripheral blood mononuclear cells (PBMC). These B-cells are monoclonal as defined by light chain expression and by the existence of rearranged Ig genes (Southern blot analysis), although they exhibit heterogeneity in the density of surface light chain. Unlike normal PBMC B-cells, the monoclonal B-cells bear CD5 and CD10 (CALLA), express adhesion and adhesion-related molecules (CD11b, CD9), and appear to be actively differentiating during the course of the disease, based on the pattern of CD45 isoform expression. At any given point in time, the population of monoclonal B-cells is heterogeneous in differentiation stage based on transitions in the expression of CD45 isoforms from expression of CD45RA, the high molecular mass isoforms of CD45, to the low molecular mass isoform CD45R0 which appears only on very late stage B-cells and early plasma cells. For one patient, analysis of CD45 isoform expression over 2 years showed that the monoclonal B-cell population as a whole progressed towards terminal differentiation as defined by loss of CD45RA and acquisition of CD45R0. This indicates a continuously differentiating lineage of an unusual B-cell phenotype, and/or malignant transformation of a distinct lineage of B-cells in WM.

Abnormalities in lymphocyte profile and specificity repertoire of patients with Waldenstrom's macroglobulinemia, multiple myeloma, and IgM monoclonal gammopathy of undetermined significance

The characteristics of T and B lymphocyte profile and B lymphocyte specificity repertoire were compared in patients with Waldenstrom's macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (IgM MGUS), multiple myeloma (MM), and age-matched normal subjects. Patients with MM had both significantly reduced frequency and number of sIg+ (surface Ig) B cells, whereas patients with WM and IgM MGUS had a reduced frequency but normal numbers of sIg+ B cells in circulation as detected in a capping assay. WM was distinguished by the large numbers of cells in the peripheral blood lymphocyte (PBL) pool that expressed CD9 (BA-2) and CD24 (BA-1) and were monoclonal, based on light chain analysis using flow cytometry. The profile of T lineage cells showed that the ratio of CD4:CD8 was significantly reduced in both MM and WM due to a reduction in the CD4 set. The CD4+ cells were qualitatively abnormal as well, with an enriched proportion of the 4B4+ (CDw29) subset and decreased proportion of the Lp220+ (CD45R) subset. This appeared to be an effect of the disease process on the relatively immature Lp220+ set. From clonal analysis, those patients with WM or IgM MGUS (unlike MM patients) did not exhibit enhanced reactivity with auto-Ig determinants, and most WM patients (7/8) and half of the IgM MGUS patients (3/6) did not have enriched proportions of B cells reactive to tetanus toxoid (TT). The TT-specific B cells in both WM and IgM MGUS, in contrast to MM, appeared fully functional in secretion of anti-TT IgM in vivo. We speculate that the more severe immunodeficiency in MM may be controlled or exacerbated by the presence of an anti-Ig network. The absence of this network in WM allows a relatively more effective immune response, but the immunodeficiency that is observed in these patients involves some abnormality in normal lymphocyte differentiation (is also present in MM).

Analysis of leucocyte differentiation antigens in blood and bone marrow from patients with Waldenström's macroglobulinaemia

Peripheral blood and bone marrow mononuclear cells from 10 patients with newly diagnosed Waldenström's macroglobulinaemia were analysed for the presence of leucocyte differentiation antigens using flow cytometry. Most patients had circulating intracytoplasmic-mu cells that were positive for the B-cell specific antigens B1, B2 and B4 and for the plasma cell antigen PCA-1. When such monoclonal cyto-mu + cells were purified by immune rosette depletion they were shown to express B1 to a much lesser extent than B2, B4 and PCA-1. In bone marrow samples cells with a similar phenotype, but with higher B1 expression were found in all patients. When the serum IgM paraprotein concentrations were compared to surface markers longitudinally from presentation and during the first courses of chemotherapy, a decreased serum IgM level was accompanied by a decrease in B1 cells in peripheral blood. These data demonstrate that WM cells possess a unique phenotype with coexpression of B-cell and plasma cell associated antigens.

Dissection of the human antigammaglobulin idiotype system with monoclonal antibodies

Murine monoclonal antibodies (MoAb) were prepared by immunizing mice with human monoclonal rheumatoid factors from patients with mixed cryoglobulinaemia. Indirect solid phase radioimmunoassay and haemagglutination inhibition were used to screen the MoAb. Reactivity patterns of MoAb were determined using (a) polyclonal and monoclonal IgM proteins, (b) monoclonal IgM proteins from patients with neuropathy, (c) monoclonal and polyclonal IgM antigammaglobulins, and (d) various isolated VkIIIb-positive immunoglobulins. Several patterns were obtained: MoAb reacting with private idiotypic determinants, with VkIIIb-related determinants, and with cross-reactive idiotypes (CRI). Two MoAb of the second type reacted with VkIIIb-positive immunoglobulins and light chains regardless of their antigenic activity. Another MoAb reacted with VkIII light chains only when in association with mu heavy chains. MoAb of the third type defined distinct CRI systems. One of these was restricted to antigammaglobulins and another also involved neuropathy-associated monoclonal IgM proteins. All MoAb clearly reacted with a minor population of normal polyclonal IgM, except for the MoAb detecting private idiotypic determinants. Studies using inhibition of binding by enzyme-linked immunosorbent assay showed that polyclonal IgM antigammaglobulins may carry a CRI determinant detected by one of the MoAb. This CRI system, defined by the MoAb Glo 86.3, was similar to but not identical with the previously described Wa CRI, which is widely prevalent among IgM antigammaglobulins of rheumatoid arthritis.

T cells in monoclonal gammopathies

Subpopulations of human T lymphocytes were analysed by monoclonal antibodies (OKT3, OKT4, OKT8) in healthy controls and in patients with multiple myeloma (MM), Waldenström's macroglobulinemia (WM) and benign monoclonal gammopathy (BMG). Lymphocytes forming rosettes with SRBC correlated well with T cells staining in indirect immunofluorescence by OKT3 monoclonal antibodies. The relative and absolute numbers of OKT4+ T cells were significantly lower in patients than in controls. Though, the percentage of OKT8+ T cells was increased in patients, the total OKT8+ cell counts were normal in all patient groups. The ratio between OKT4+ and OKT8+ lymphocytes was low in the groups of treated MM and of WM patients compared to controls (P less than 0.001). Moreover, the ratio was lower than the normal range in 27% of BMG and 38% of untreated MM patients. The imbalance between OKT4+ and OKT8+ T cells in untreated MM was more pronounced in clinical stage III patients than in stage I and II patients. The most pronounced changes were noted in treated MM patients. The significance of the altered T cell subsets in monoclonal gammopathies with regard to polyclonal and tumor B cell regulation remains to be established.

Monoclonal blood lymphocytes in benign monoclonal gammopathy and multiple myeloma in relation to clinical stage

20 patients with benign monoclonal gammopathy (BMG) have been studied for blood lymphocyte and subpopulations. 4 patients had slightly decreased T-lymphocyte values. Total B-lymphocytes were within the normal range. In 3 BMG patients an abnormal ratio between kappa- and lambda-bearing lymphocytes was detected indicating circulating monoclonal cells. 41 lymphoid cells using the kappa: lambda-ratio. 54% of the patients had monoclonal blood cells at diagnosis. the incidence and numbers of such cells increased with advanced clinical stage. Thus, it seems as if tumor volume is the main factor responsible for the appearance of monoclonal blood cells in multiple myeloma.

Clinical significance of immunoglobulin-secreting cells in the peripheral blood in patients with multiple myeloma

Immunoglobulin-secreting cells were enumerated in the peripheral blood of 31 patients with multiple myeloma, nine patients with so-called benign monoclonal gammopathy, and ten patients with polyclonal hypergammaglobulinaemia or idiopathic hypogammaglobulinaemia. Immunoglobulin-secreting cells were detected by a haemolytic plaque assay using protein-A-coated erythrocytes in the presence of class- or type-specific rabbit anti-human immunoglobulin antisera. In about two-thirds of patients with multiple myeloma, cells secreting the same light-chain isotype of their serum M-protein increased in number, whereas this was not the case in the patients with so-called benign monoclonal gammopathy. Follow-up studies of immunoglobulin-secreting cells in multiple myeloma revealed that these cells increased or decreased, correlating with the severity of the disease, and alterations were more rapid than other clinical features. This plaque assay is therefore useful in evaluating the response to chemotherapy in patients with multiple myeloma.