2 Bone marrow B cell development

Intermediate lymphocytic lymphoma: an immunohistologic study with comparison to other lymphocytic lymphomas

In an immunohistologic analysis of 13 cases of intermediate lymphocytic lymphoma (ILL), the immunophenotype of ILL was compared to the immunophenotypes of other B-lymphocytic lymphomas and the normal lymphoid follicle to determine the normal cell in the scheme of B-cell differentiation that corresponds to ILL. The characteristic immunophenotype of ILL was surface IgM +/- D+, cytoplasmic immunoglobulin -, B1+, BA1+, B2-, BA2-, B4+, Leu 14+, HLA-DR+, Leu 1+, and common acute lymphoblastic leukemia associated (CALLA) antigen -. The immunophenotype of ILL was similar to that of lymphocytes in normal primary follicles and the mantle zones of secondary follicles. The "immature" phenotype of ILL was identical to that of small lymphocytic lymphoma, which strongly supports their close lineage relationship. In contrast, the "mature" phenotypes of the follicular center cell and lymphoplasmacytoid lymphomas suggest that they correspond to normal cells at later stages of differentiation. Our findings indicate that B-lymphocytic lymphomas recapitulate the normal stages of B-cell differentiation. The cell of ILL appears to be an immature B cell that homes to, and resides in, primary follicles and the mantle zones of secondary follicles. The cytologic, architectural, immunologic, and clinical features of ILL indicate that it should be included as a separate category in the International Working Formulation.

Human leukocyte function-associated antigens on lympho-hemopoietic precursor cells

The expression of human leukocyte function-associated antigens (HLFA, equivalents of murine LFA-1) was studied on early lympho-hemopoietic cells in infant thymus and normal bone marrow by double immunofluorescence methods, cell sorting and colony-forming assays. Monoclonal antibodies MHM-24 recognizing the alpha chain (180 kDa) and 60.3 and 60.1 identifying the beta chain (95 kDa) were used. The vast majority of thymocytes including large terminal deoxynucleotidyl transferase (TdT)-positive blast cells are HLFA positive. On the other hand, most B cell precursors in the bone marrow, identified by the expression of nuclear TdT, do not show surface HLFA which appears at the pre-B cell stage (cytoplasmic mu positive, surface Ig negative). Cell sorting experiments revealed an enrichment of early myeloid cells (myeloblasts and colony-forming unit cells) in the HLFA-negative fraction. Erythroid cells appeared to be completely negative from the burst-forming unit erythrocyte stage onwards. Anti-HLFA-antibodies, capable of blocking T cell and natural killer function, may have therapeutic potential without interfering with precursor cell development in man.

Immunological phenotype of neoplasms involving the B cell in the last step of differentiation

The immunological phenotype of diseases involving the last step of B cell differentiation--multiple myeloma (MM, 38 patients) and Waldenström's macroglobulinaemia (WM, 12 patients)--was analysed with a panel of monoclonal antibodies (McAb) as well as conventional markers. Most of the bone marrow plasma cells (80%) from MM patients reacted with the McAb OKT10, FMC8 and FMC48. Plasma cells were consistently negative with FMC7, Leu-1 and mouse rosettes. Ia, B1 and SIg were expressed in a minority of plasma cells (less than 30%) in half of the cases. The circulating neoplastic cells from five MM patients showed a more immature phenotype, with a higher reactivity for OKIa, B1 and increased SIg and a lower expression of CIg, than bone marrow plasma cells. The malignant cells of WM patients differed from those of MM in the reactivity with FMC7, being positive in 10 out of 11 cases, and in their high expression of B1, Ia and SIg with a predominant mu+ phenotype. Mouse rosettes and Leu-1 were positive in one case; OKT10 was positive in three out of five WM patients studied. This phenotype indicates that WM cells correspond to an earlier stage of B cell differentiation than MM plasma cells. The McAb J5 was positive in three out of six MM and two out of four WM analysed. The antigenic differences observed in MM and WM patients support the notion that the cells of the neoplastic clone are able to undergo a certain degree of differentiation.

Analysis of gene expression during hematopoiesis: present and future applications

Recombinant DNA technology now provides the strategies required to identify genes whose expression controls the development of normal and pathologic blood cells. Characterization of the gene families responsible for synthesis of hemoglobins, immunoglobulins, histocompatibility antigens, and cellular enzymes have already, or are about to, provide major insights into the mechanisms producing normal erythroid cells, immunocytes, and immune surface features. Hemoglobinopathies, leukemias, and autoimmune diseases of the bone marrow can now be examined to a degree of detail previously inaccessible to investigators. Oncogene translocation analysis is shedding new light on the pathogenesis of leukemias and lymphomas. Recent basic advances now permit direct cloning and identification of genes in host organisms which express their protein products, thus allowing isolation of genes coding for the hematopoietic surface markers and growth factors which characterize and regulate blood cell progenitors. This review summarizes the molecular genetic approach to analysis of normal and pathologic hematopoiesis, surveys major findings which have resulted, and examines the potential use of refined gene cloning strategies for improved understanding of blood cell development.

Heterogeneity of human B lymphocytes as revealed by monoclonal antibodies

Two monoclonal antibodies directed at determinants on human B lymphocytes were produced and characterized by indirect immunofluorescence. The antibodies, BL13 and BL14, were found to be specific for B cells, since they did not react on red cells, platelets, granulocytes, monocytes or T lymphocytes. BL14-associated antigen was present on most of the circulating and tissular B cells, whereas that detected by BL13 was mainly restricted to a subpopulation preferentially homed in germinal centers of secondary follicles of lymph nodes and tonsils, which did not circulate under normal conditions and disappeared once B cells were activated by mitogens. Immunoprecipitation studies demonstrated that BL13 precipitated an antigen of approximately 160,000 d. Pathological studies confirmed the specificity of BL13 and BL14 antibodies for B lymphocytes, since they never reacted with non-B malignancies. BL14 bound to nearly all malignant B-cell proliferations except very immature and plasmacytoma cells. In contrast, BL13 was always found to be negative on acute lymphocytic leukaemias, prolymphocytic leukaemias, hairy cell leukaemias and plasma cells, whereas it detected 40-50% of chronic lymphocytic leukaemias and Burkitt or non-Burkitt lymphomas. These results led us to hypothesize several compartments for B-lymphocyte differentiation, either in central (bone marrow) or peripheral lymphoid organs, with BL13 antibody defining one compartment in the germinal centers.

Intracellular inclusion bodies in 14 patients with B cell lymphoproliferative disorders

Two types of intracytoplasmic inclusion were detected by immunofluorescence microscopy in 12 patients with chronic lymphocytic leukaemia and two patients with a leukaemic phase of well differentiated lymphocytic lymphoma. Further analysis with light- and electron microscopy, showed that most inclusion bodies were rod-like crystalline structures. However, in three patients they consisted of amorphous vesicular precipitates. Immunological studies revealed the presence of immunoglobulins of the same class and type at the cell surface as well as in the inclusion bodies. The monoclonal immunoglobulins were all of lambda type except in two cases. The origin of immunoglobulin inclusion bodies in B cell malignancies is discussed in relation to published data and our own observation in one patient followed during treatment.