Normal and abnormal regulation of human B cell differentiation by a new cytokine, BSF2/IL-6.
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Amino Acid Sequence↗
Biomedical subjects
A Muraguchi
Publications and source records attributed to A Muraguchi.
A multifunctional cytokine (IL-6/BSF-2) and its receptor.
Interleukin 6 (IL-6)/B cell stimulatory factor 2 is a multifunctional cytokine produced by both lymphoid and nonlymphoid cells. IL-6 regulates immune response, acute phase reaction, and hematopoiesis. It was found that IL-6 production by T cells is dependent on macrophages, and IL-6 is one of essential factors for pokeweed mitogen induced immunoglobulin production. Both high- and low-affinity IL-6 receptors were identified. The molecular cloning of IL-6 receptors demonstrated that this receptor is a member of the immunoglobulin superfamily. The deregulated production of IL-6 is suggested to be involved in the pathogenesis of autoimmune diseases and in the development of multiple myeloma.
Animals↗
Biphenotypic leukemic lymphocyte precursors in CD2+CD19+ acute lymphoblastic leukemia and their putative normal counterparts in human fetal hematopoietic tissues.
During detailed immunophenotypic analyses of marrow blasts from 336 acute lymphoblastic leukemia (ALL) patients, a very small percentage of cases reactive with B-cell-directed as well as T-cell-directed monoclonal antibodies (MoAbs) were identified. Five ALL cases were biphenotypic since they coexpressed CD2 (Tp50) and CD19 (Bp95) antigens at the single-cell level. The composite immunophenotype of these biphenotypic ALL cases was [TdT+HLA-ABC+CD2+CD3-CD10+CD13-CD14-CD16-CD19+CD20+ ++-CD21-CD33-CD34+Bgp95-C mu- slg-]. Low-molecular-weight B-cell growth factor (LMW-BCGF), recombinant interleukin-2 (rIL-2), and rIL-3 stimulated the proliferative activity of biphenotypic leukemic lymphocyte precursors without inducing differentiation. In the presence of the phorbol ester TPA, leukemic blasts from two cases differentiated along the B precursor pathway to the [CD2-CD10+CD19+CD20+C mu+slg-] pre-B cell stage. Biphenotypic ALL cases did not share a common configuration and gene rearrangement pattern of the immunoglobulin heavy chain genes or T-cell receptor (TCR) genes. Three cases had rearranged C mu genes but germline TCR genes, one case showed rearrangement of both C mu and TCR genes, and the remaining case had rearranged TCR genes but germline C mu genes. All five patients attained prompt remission after standard induction chemotherapy. Three to four years after initial diagnosis, four patients are now off chemotherapy and remain alive in their first remission. One patient relapsed at 3 years, 7 months, but promptly achieved complete remission after reinduction chemotherapy and remains in second remission off chemotherapy greater than 3 years after her reinduction therapy. With two-color immunofluorescence staining techniques and multiparameter flow cytometric analyses, we identified a small population of CD2+CD19+ lymphoid cells in fetal livers (FLs) and fetal bone marrows (FBMs), which may represent the putative normal counterparts of biphenotypic ALL blasts. A CD2+CD19+ normal biphenotypic lymphoid precursor cell line, designated FL 8.2 CD2+, was established from an FL of 8-weeks of gestational age by Epstein-Barr virus (EBV)-induced blastoid transformation. The composite immunophenotype of FL 8.2 CD2+ cell line was [TdT+HLA-ABC+HLA-DR+ CD2+CD5-CD7-CD10+/-CD13-CD19+CD20-CD21+ CD22+CD33-CD34+/-Bgp95-CDw40+C mu-slgD-slgM-]. FL 8.2 CD2+ cells showed germline patterns of immunoglobulin heavy-chain joining region, heavy-chain constant region, kappa light-chain constant region genes, and TCR beta-chain genes. Cross-linking of CD2 as well as CD19 antigens on FL 8.2 CD2+ cells caused an increase of intracellular ionized calcium.(ABSTRACT TRUNCATED AT 400 WORDS)
Antibodies, Monoclonal↗
Regulation of BSF-2/IL-6 production by human mononuclear cells. Macrophage-dependent synthesis of BSF-2/IL-6 by T cells.
Regulation of BSF-2/IL-6 production in peripheral mononuclear cells (MNC) was studied. BSF-2 mRNA expression in mitogen-stimulated MNC showed a biphasic response, the first peak around 4 h and the second peak around 48 h. This was caused by different kinetics of BSF-2 mRNA expression in distinct subpopulations of MNC; M phi expressed BSF-2 mRNA at 5 h in the absence of any stimulation, and mitogen-stimulated T cells and B cells expressed BSF-2 mRNA 48 h after stimulation. Immunohistochemical staining of the cells with anti-BSF-2 antibody demonstrated that macrophages, T cells and B cells could produce BSF-2. T cells in peripheral MNC produced BSF-2 in the presence of M phi. The requirement of macrophage for BSF-2 production in T cells could be replaced by TPA but not by IL-1 or BSF-2.
B-Lymphocytes↗
The essential role of B cell stimulatory factor 2 (BSF-2/IL-6) for the terminal differentiation of B cells.
The role of recombinant B cell stimulatory factor 2 (BSF-2/IL-6) in the regulation of growth and differentiation of B cells was investigated. rBSF-2 at 200 pg/ml could induce 50% of the maximum Ig production in B lymphoblastoid cell lines, the specific activity being estimated as 5 X 10(6) U/mg. rBSF-2 augmented PWM-induced IgM, IgG, and IgA production in mononuclear cells (MNC); the effect was exerted by directly acting on PWM-induced B blast cells to induce Ig production. However, rBSF-2 did not induce any growth of activated B cells. In contrast, rBSF-2 showed a potent growth activity on a murine hybridoma clone, MH60.BSF2. The concentration required for half-maximal [3H]TdR uptake was approximately 5 pg/ml, which was 40 times less than that required for Ig induction in a B cell line. Anti-BSF-2 antibody inhibited PWM-induced Ig production in MNC, but not PWM-induced proliferation. The antibody was effective even when added on day 4 of an 8-d culture, indicating that BSF-2 is one of the essential late-acting factors in PWM-induced Ig production.
Antibodies↗
Delineation of human B cell differentiation: immunological and molecular characterization of human B cell differentiation factor (BSF-2).
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B-Lymphocytes↗
B cell-derived BCGF functions as autocrine growth factor(s) in normal and transformed B lymphocytes.
This paper demonstrates that B cell lines, as well as normal activated B cells generate and respond to B cell-specific growth factor(s) (BCGF). BCGF derived from B cells (B-BCGF) appears to be distinct from interleukin 1, interleukin 2 (IL 2), B cell stimulatory factor, BCGF-II, interferon-gamma, or transforming growth factor. It acts on activated B cells, but not on resting G0 phase B cells to induce proliferation. B cell lines, immortalized by Epstein-Barr virus, constitutively secrete 10-fold higher level of B-BCGF compared with normal activated B cells, suggesting that an activated autocrine loop might be operating in immortalized B cells. On the basis of our observations, we postulate that B cell clonal expansion may occur, at least in part, through a B-BCGF-dependent autocrine pathway similar to IL 2 effect on T cells.
Adjuvants, Immunologic↗
Expression and function of an early activation marker restricted to human B cells.
A B cell-specific monoclonal antibody (anti-Ba) was prepared. In two-color FACS analysis the anti-Ba reacted with a subpopulation of Ig+ or B1+ cells obtained from tonsils, but did not react with most B1+ cells derived from PBL. Activation of B cells from PBL with TPA or anti-mu induced Ba expression and the addition of PHA-conditioned supernatant with anti-mu-enhanced Ba expression. Other B cell activators, such as Staphylococcus aureus Cowan I (Staph-A) or PWM plus T cells, could induce Ba expression. Ba expression was observed 6 hr after stimulation and reached a peak level at 72 hr. Ba expression was strictly restricted to B cells. H-7, a specific inhibitor of protein kinase C (C-kinase), displayed a dose-dependent inhibitory effect on Ba expression, showing dependency on C-kinase for Ba expression. Anti-Ba inhibited B cell proliferation induced by anti-mu and B-BCGF distinct from BSF-1. The results presented in this study suggest that the Ba antigen on B cells may be comparable to the Tac antigen on T cells.
Animals↗
A case of human B cell leukemia that implicates an autocrine mechanism in the abnormal growth of Leu 1 B cells.
Production of B cell growth factor (BCGF) from B-chronic lymphocytic leukemia (B-CLL) cells was demonstrated. Freshly isolated monoclonal B-CLL cells expressed surface mu, delta, B1, and Leu 1, but not Ba (an antigen expressed only on activated B cells). Upon stimulation with anti-IgM, they secreted BCGF, which could act on anti-IgM-stimulated autologous leukemic cells as well as anti-IgM-stimulated normal B cells. Cell lines established from these leukemic cells also constitutively secreted BCGF. The BCGF from B-CLL cells or established cell lines induced neither proliferation nor enhanced HLA-DR expression in resting B cells. These results show the presence of B cell-derived BCGF, which is distinct from BSF-1 and effective only on activated B cells. They also suggest that an autocrine mechanism may operate in the growth of B-CLL cells.
Antigens, Surface↗
Kappa-chain gene rearrangement in an apparent T-lineage lymphoma.
We describe a 10-yr-old boy with T-lineage non-Hodgkin's lymphoma. He had a mediastinal mass, swollen supraclavicular lymph nodes, and pleural effusion. A supraclavicular lymph node biopsy under light microscopy showed a malignant lymphoma of diffuse lymphoblastic type. Most of the cells taken from the malignant pleural effusion expressed T cell-associated antigens such as Leu-1 and OKT 8. To confirm these antigens as T-lineage lymphoma, we examined genomic DNA from malignant cells obtained from the pleural effusion. As was expected, T cell receptor beta-chain gene rearrangements were demonstrated. However, when the immunoglobulin gene organization was analyzed, we detected rearrangements in both the heavy- and kappa-chain genes. To our knowledge, this is the first case in which kappa-chain gene rearrangement was detected in apparent T-lineage cells. These findings provide important information relating to determination of the cellular lineage of lymphoid malignancy.
Child↗
[Protein and polypeptide growth factors--B lymphocyte growth and differentiation factor].
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Animals↗
Interleukin 2 receptors on human B cells. Implications for the role of interleukin 2 in human B cell function.
In the present study, we examined the expression of interleukin 2 (IL-2) receptors on normal human B cells as well as established B cell lines. Anti-Tac monoclonal antibody did not bind to freshly separated normal human B cells. Unexpectedly, with the appropriate activation of the normal B cells by anti-mu antibody, phorbol myristate acetate, or Staphylococcus aureus Cowan I (SAC), Tac antigen was induced on the activated B cells. Anti-Tac antibody showed consistent reactivity with two B cell lines that were infected by human T cell leukemia virus (HTLV) and some reactivity with two out of eight Epstein-Barr virus-transformed B cell lines established from normal adult donors. Immunoprecipitation analysis revealed that antigens of similar size with a molecular weight of 50,000-60,000 can be precipitated with anti-Tac antibody from phytohemagglutinin-stimulated normal T cell blasts and normal activated B cells, as well as a cloned B cell line. Binding assays of IL-2 on normal activated B cells and on the cloned B cell (HS1) revealed that B cells have significantly fewer sites and lower-affinity IL-2 receptors compared with phytohemagglutinin-stimulated normal T cell blasts. Finally, biological properties of the IL-2 receptor on B cells were examined by incubating B cells with recombinant IL-2. It was found that moderate concentrations of IL-2 induce significant enhancement of proliferation and differentiation in SAC-activated normal B cells. These results suggest that normal B cells may express functional IL-2 receptors or closely related proteins and thus IL-2 may play a significant role in the modulation of B cell function.
Adolescent↗
The modulation of membrane Ia on human B lymphocytes.
Using flow cytometry techniques, changes in surface Ia (DR and DS) expression on human B lymphocytes were correlated with changes in the cell cycle following stimulation with anti-mu. The effect of interleukin (IL)-1, IL-2, B-cell growth factor (BCGF), and interferons on Ia expression on resting B cells was also examined. A population of resting B lymphocytes was cultured in vitro with 100 micrograms/ml of anti-mu and immunofluorescently stained for DR and DS at various times following stimulation. Detectable increases in DR and DS expression were found within 8 hr, and the major increases (twofold and fourfold) in DR and DS expression occurred over the next 48 hr. Using cell cycle inhibitors and propidium iodide staining, it was demonstrated that the enhanced DR and DS expression following anti-mu stimulation began during G0 to G1 transition and increased as the cells progressed through G1 phase. During S and G2/M phases, there were minimal further increases in surface Ia. Although prolonged exposure of B cells to anti-mu was required for cellular activation, cell size enlargement, and progression into S phase, a brief exposure to anti-mu, insufficient for cellular activation, markedly enhanced Ia expression. Thus anti-mu-stimulated resting human B lymphocytes rapidly increase their surface Ia expression. This increase occurs predominantly prior to entrance into S phase and can occur in the absence of significant cellular activation. Interferons have been reported to modulate surface Ia expression on a human lymphoid cell line and on monocytes and supernatants with BCGF activity to enhance surface Ia expression on murine B cells; however, neither alpha-interferon, gamma-interferon, IL-1, IL-2, nor BCGF modified surface DR expression on normal resting human B cells.
Antibodies, Anti-Idiotypic↗
The direct effects of interleukin 1, interleukin 2, interferon-alpha, interferon-gamma, B-cell growth factor, and a B-cell differentiation factor on resting and activated human B cells.
A wide variety of cytokines have been demonstrated to affect B-cell function. However, it is unclear which of these mediators actually exert direct effects on the B cells themselves. In the present study, the direct role of interleukin (IL) 1, IL-2, Interferon-gamma, or Interferon-alpha in human B-cell activation, proliferation, or differentiation was examined and compared with the effects of a B-cell growth factor (BCGF) or a B-cell differentiation factor (BCDF). Highly purified human B lymphocytes were separated according to size into two nonoverlapping populations. The fraction of small B cells was incubated with IL-1, IL-2, Interferon-gamma, Interferon-alpha, BCGF, or BCDF, and cell size changes, RNA synthesis, DNA synthesis, or supernatant immunoglobulin (Ig) production were measured. Neither IL-1, IL-2, Interferon-alpha, Interferon-gamma, nor the BCGF induced substantial cell size changes, RNA synthesis, DNA synthesis, or Ig production by the small fraction of B lymphocytes; however, the BCDF could directly activate a proportion of resting B lymphocytes to secrete Ig. The fraction of large B cells was also incubated with these cytokines. While neither IL-1, Interferon-alpha, nor Interferon-gamma enhanced DNA synthesis or Ig production by the fraction of large B lymphocytes, DNA synthesis was augmented 23-fold by BCGF and IgG production was increased 7-fold by BCDF. Additionally, IL-2 slightly enhanced both proliferation and differentiation of large B cells but substantially less so than BCGF and BCDF; DNA synthesis was increased 4-fold, while Ig production in the presence of IL-2 was increased by approximately 50%. Thus, the most important lymphokines modulating the function of these two fractions of tonsillar lymphocytes were a BCGF and a BCDF.
B-Lymphocytes↗
Induction of IgG secretion in a human B cell clone with recombinant IL 2.
A human B cell clone (SGB3) responsive to IL 2 was established. Both recombinant IL 2 and B cell differentiation factor (BCDF) induced IgG secretion in SGB3 cells in a dose-dependent manner, but IL 2 did not affect the proliferation of SGB3 cells. FACS analysis showed that SGB3 cells expressed Tac antigen and anti-Tac antibody inhibited IL 2-induced IgG secretion without any inhibitory effect on BCDF-induced IgG secretion. These results showed that IL 2 could directly act on B cells and provide a differentiation signal through IL 2 receptors distinct from BCDF receptors. Physiologic relevance of IL 2 in the antibody response was discussed.
Animals↗
Human B cell activation and cell cycle progression: stimulation with anti-mu and Staphylococcus aureus Cowan strain I.
The responses of resting human B lymphocytes to a variety of activation signals were studied. Human tonsillar B lymphocytes were separated according to size by countercurrent elutriation. The small B lymphocytes were then stimulated in vitro with various concentrations of anti-mu antibody in the presence or absence of B cell growth factor (BCGF) or with Staphylococcus aureus Cowan strain I (SAC). Cellular volume changes and RNA synthesis were measured over the first 24 h of stimulation and were similar with either 15 micrograms/ml of anti-mu, 100 micrograms/ml of anti-mu, or SAC. In the subsequent 24 h, however, substantial increases occurred in the amount of RNA synthesis and cell enlargement only in those cultures stimulated with 100 micrograms/ml of anti-mu or SAC, but not in the cultures stimulated with 15 micrograms/ml of anti-mu. The addition of BCGF to those cultures stimulated with 15 micrograms/ml of anti-mu did not alter the increases in cellular volume and RNA synthesis found 24 h after stimulation with anti-mu alone. However, over the subsequent 24 h, the presence of BCGF in culture enhanced both B cell volume changes and RNA synthesis, when compared to cultures stimulated with 15 micrograms/ml of anti-mu alone. In addition, BCGF enhanced DNA synthesis in cultures stimulated with low and high concentrations of anti-mu. DNA content changes following stimulation with anti-mu, anti-mu plus BCGF, and SAC were also measured using propidium iodide staining and flow cytometry. Optimal concentrations of anti-mu induced 20% of the resting B cells to enter S phase, while optimal concentrations of anti-mu plus BCGF or SAC induced approximately 40%. Finally, prestimulation of resting B cells for 24 h with a low concentration of anti-mu, sufficient for cell enlargement but not S phase progression, allowed for rapid entrance of the prestimulated B cells into S phase when a high concentration of anti-mu or SAC was added. These findings suggest the existence of a control point in the progression of human B cells through the cell cycle. This control point is located in the G1 phase of the cycle and is reached 24 to 36 h after a surface immunoglobulin-mediated stimulus.
Antibodies, Anti-Idiotypic↗
Regulation of human B-cell activation, proliferation, and differentiation by soluble factors.
This review describes a series of studies performed in our laboratory which have focused on the activation and subsequent proliferation and differentiation of human B lymphocytes. Utilizing polyclonal signals which activate B cells by interacting with their surface membrane Ig, we have examined the events in the transition of a resting B lymphocyte to an Ig-secreting cell. A major theme in these studies is the role of soluble factors in B cell proliferation and B cell differentiation. Specific B cell growth and differentiation factors are described. Data on their sources, biochemical characterization, and methods of assay are included. Additionally, the potential role of interleukin 2 in human B cell function is discussed. The recognition that B cells exist in a variety of activation states and that transition between different states is dependent upon different signals was the impetus for a series of studies which more precisely delineated these states and the signals involved. These findings and the observations from other investigators led to a proposed model of the sequential steps in a factor-dependent B cell differentiation pathway. This model is discussed and related to the mechanisms of T cell activation and growth. Finally, the effects of two pharmacologic agents, glucocorticoids and cyclosporin A, on human B cell function are described and discussed in the context of this model.
Antigens, Differentiation, B-Lymphocyte↗
Human B cell activation, proliferation and differentiation.
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Animals↗