Human B cell differentiation. IV. Effect of monoclonal anti-immunoglobulin M and D antibodies on B cell proliferation and differentiation induced by T cell factors

Monoclonal anti-mu and anti-delta antibodies and mixed lymphocyte reaction-derived T cell factors (MLR-TF) were examined alone and in combination for their effects on proliferation and differentiation of human B cells. MLR-TF induced proliferation and subsequent plasma cell differentiation of blood B cells without additional stimulation. The monoclonal anti-mu and anti-delta antibodies alone did not induce proliferation, but each was capable of augmenting B cell proliferation induced by MLR-TF. In contrast, the anti-mu antibody inhibited the MLR-TF induction of IgM plasma cell differentiation but did not affect the differentiation of IgG and IgA plasma cells. The anti-delta antibody had no effect on MLR-TF-induced plasma cell differentiation. Studies using density gradient separation of B cell subpopulations suggest that MLR-TF induce low-density B cells to proliferate and differentiate into plasma cells but that by themselves MLR-TF have little effect on B cells of relatively high density. The latter subpopulation of small resting B cells responded with proliferation to MLR-TF when combined with either the anti-mu or the anti-delta antibody, but these stimuli were insufficient for induction of terminal plasma cell differentiation.

IgG subclass expression by human B lymphocytes and plasma cells: B lymphocytes precommitted to IgG subclass can be preferentially induced by polyclonal mitogens with T cell help

The human IgG subclasses expressed by circulating B lymphocytes, tissue plasma cells, and plasma cells generated from B cell precursors in response to the polyclonal mitogens LPS and PWM were examined by immunofluorescence using subclass-specific monoclonal antibodies. The subclass distribution observed for circulating B lymphocytes was IgG2 (48%) greater than IgG1 (40%) greater than IgG3 (8%) greater than IgG4 (1%), while the distribution among IgG plasma cells in bone marrow, blood, spleen, and tonsils was IgG1 (64%) greater than IgG2 (26%) greater than IgG3 (8%) greater than IgG4 (1%). Multiple IgG isotypes were not observed on B cells or in plasma cells. Although IgG plasma cell responses to both LPS and PWM were T cell dependent, the distributions of IgG subclasses elicited were strikingly different. In control and LPS-stimulated cultures of blood mononuclear cells, the induced plasma cells expressed the IgG subclass distribution: IgG2 greater than 80%, IgG1 less than 20%, IgG3 less than 1%, IgG4 less than 1%. In PWM-stimulated cultures, the subclass distribution, IgG1 approximately 65%, IgG2 approximately 25%, IgG3 approximately 7%, IgG4 approximately 1%, was in perfect concordance with the in vivo subclass distribution of IgG plasma cells. Selective inhibition of suppressor T cell activity by x-irradiation and mitomycin C treatment did not alter the IgG subclass distribution pattern induced by LPS and PWM. Monoclonal antibodies were used to deplete selectively the B cell precursors bearing IgG1, IgG2, or IgG3 before PWM stimulation of blood mononuclear cells. In each instance, a reduction was observed only in the subpopulation of plasma cells producing the homologous IgG subclass. The results indicate that T cells can preferentially influence the terminal differentiation of B cells that are precommitted to different IgG subclasses.

IgG subclass expression by human B lymphocytes and plasma cells: B lymphocytes precommitted to IgG subclass can be preferentially induced by polyclonal mitogens with T cell help

The human IgG subclasses expressed by circulating B lymphocytes, tissue plasma cells, and plasma cells generated from B cell precursors in response to the polyclonal mitogens LPS and PWM were examined by immunofluorescence using subclass-specific monoclonal antibodies. The subclass distribution observed for circulating B lymphocytes was IgG2 (48%) greater than IgG1 (40%) greater than IgG3 (8%) greater than IgG4 (1%), while the distribution among IgG plasma cells in bone marrow, blood, spleen, and tonsils was IgG1 (64%) greater than IgG2 (26%) greater than IgG3 (8%) greater than IgG4 (1%). Multiple IgG isotypes were not observed on B cells or in plasma cells. Although IgG plasma cell responses to both LPS and PWM were T cell dependent, the distributions of IgG subclasses elicited were strikingly different. In control and LPS-stimulated cultures of blood mononuclear cells, the induced plasma cells expressed the IgG subclass distribution: IgG2 greater than 80%, IgG1 less than 20%, IgG3 less than 1%, IgG4 less than 1%. In PWM-stimulated cultures, the subclass distribution, IgG1 approximately 65%, IgG2 approximately 25%, IgG3 approximately 7%, IgG4 approximately 1%, was in perfect concordance with the in vivo subclass distribution of IgG plasma cells. Selective inhibition of suppressor T cell activity by x-irradiation and mitomycin C treatment did not alter the IgG subclass distribution pattern induced by LPS and PWM. Monoclonal antibodies were used to deplete selectively the B cell precursors bearing IgG1, IgG2, or IgG3 before PWM stimulation of blood mononuclear cells. In each instance, a reduction was observed only in the subpopulation of plasma cells producing the homologous IgG subclass. The results indicate that T cells can preferentially influence the terminal differentiation of B cells that are precommitted to different IgG subclasses.

Human B cell differentiation. III. Enhancing effect of monoclonal anti-immunoglobulin D antibody on pokeweed mitogen-induced plasma cell differentiation

The effects of monoclonal anti-delta antibodies on pokeweed mitogen (PWM) responses of blood mononuclear cells (MNC) were studied. Treatment with anti-delta antibody enhanced both B cell proliferation and plasma cell differentiation, which are T cell-dependent responses. The anti-delta enhancement of plasma cell differentiation, predominantly of IgM plasma cells, was surprising because PWM-responsive subpopulations of B cells have been shown to lack IgD and their plasma cell differentiation is easily and selectively suppressed by anti-mu, -gamma and -alpha antibodies. Treatment of MNC with monoclonal anti-delta antibody enhanced the number of IgM plasma cells induced by PWM stimulation by approximately threefold. The degree of enhancement was dependent upon the concentration of anti-delta antibody, and the F(ab')2 fragments were effective. Maximal enhancement was obtained either when MNC were preincubated with anti-delta antibody for 1 day before PWM stimulation or when anti-delta antibody was added with PWM at the beginning of 7-day cultures. Anti-delta antibody had little or no effect when added 1 to 3 days after the initiation of PWM stimulated cultures. Anti-delta treatment overnight induced a population of small IgM+IgD+ B cells to enlarge and converted them from poor to good PWM responders. The results are discussed in the context of a model which proposed that differentiation of both immature and preactivated mature IgD- cells can be inhibited by signals generated via surface immunoglobulin cross-linkage, whereas this stimulus enhances differentiation of the intermediate IgD+IgM+ B cells.

Human B cell differentiation. III. Enhancing effect of monoclonal anti-immunoglobulin D antibody on pokeweed mitogen-induced plasma cell differentiation

The effects of monoclonal anti-delta antibodies on pokeweed mitogen (PWM) responses of blood mononuclear cells (MNC) were studied. Treatment with anti-delta antibody enhanced both B cell proliferation and plasma cell differentiation, which are T cell-dependent responses. The anti-delta enhancement of plasma cell differentiation, predominantly of IgM plasma cells, was surprising because PWM-responsive subpopulations of B cells have been shown to lack IgD and their plasma cell differentiation is easily and selectively suppressed by anti-mu, -gamma and -alpha antibodies. Treatment of MNC with monoclonal anti-delta antibody enhanced the number of IgM plasma cells induced by PWM stimulation by approximately threefold. The degree of enhancement was dependent upon the concentration of anti-delta antibody, and the F(ab')2 fragments were effective. Maximal enhancement was obtained either when MNC were preincubated with anti-delta antibody for 1 day before PWM stimulation or when anti-delta antibody was added with PWM at the beginning of 7-day cultures. Anti-delta antibody had little or no effect when added 1 to 3 days after the initiation of PWM stimulated cultures. Anti-delta treatment overnight induced a population of small IgM+IgD+ B cells to enlarge and converted them from poor to good PWM responders. The results are discussed in the context of a model which proposed that differentiation of both immature and preactivated mature IgD- cells can be inhibited by signals generated via surface immunoglobulin cross-linkage, whereas this stimulus enhances differentiation of the intermediate IgD+IgM+ B cells.

Human B cell differentiation. II. Pokeweed mitogen-responsive B cells belong to a surface immunoglobulin D-negative subpopulation

Surface immunoglobulin D (IgD)-positive lymphocytes precoated with monoclonal anti-delta antibody were selectively removed from blood mononuclear cell preparations by "panning" and by fluorescence-activated cell sorter. The depletion of sIgD+ cells did not significantly affect plasma cell responses to pokeweed mitogen PWM). PWM-responsive B cells lacking sIgD and mouse erythrocyte receptors preferentially sedimented in lower density fractions of a discontinuous Percoll gradient, and sIgD-negative B cells were found to have a larger mean diameter than IgD-positive cells. We conclude that PWM-responsive B cells represent a distinct subpopulation of relatively large cells that have ceased to express receptors for mouse erythrocytes and surface IgD.

Human b-cell differentiation. I. Analysis of immunoglobulin heavy chain switching using monoclonal anti-immunoglobulin M, G, and A antibodies and pokeweed mitogen-induced plasma cell differentiation

Monoclonal antibodies were used to examine the immunoglobulin isotypes expressed by B lymphocyte precursors of IgM, IgG, IgA, and IgA2 plasma cells. Plasma-cell differentiation was induced by the addition of pokeweed mitogen to cultures of blood mononuclear cells. Anti-mu, -gamma, -alpha, and -alpha 1 antibodies were used in some experiments to inhibit differentiation of B lymphocytes bearing these heavy chain isotypes, and for selective removal of B lymphocyte precursors before culture with pokeweed mitogen in other experiments. Three major subpopulations of B lymphocyte precursors were identified: (a) a subpopulation of surface (s) IgM+ precursors of IgM plasma cells that did not express IgG or IgA isotypes, (b) a subpopulation of sIgG+ precursors of IgG plasma cells of which approximately one-half bore some IgM and none had detectable IgA receptors, and (c) a subpopulation of sIgA+ precursors of IgA plasma cells; one half of these precursors could be shown to express functional IgM receptors but none were found to express IgG receptors. The sIgA subpopulation could be further subdivided into sIgA1+ precursors of IgA1 plasma cells and IgA1-negative precursors of IgA2 plasma cells. These results suggest that normal human B cells can switch from mu directly to each of the other heavy chain isotypes, and that these represent the main switch pathways.

T cell-replacing factor- (TRF) induced IgG secretion in a human B blastoid cell line and demonstration of acceptors for TRF

IgG-secretion was induced in a human B blastoid cell line, CESS, by the addition of partially purified T cell-derived helper factor(s) (TRF), which had been obtained from PHA-stimulated human T cells. The number of IgG-producing cells in CESS cells reached its maximal level (10% of total cells) within 48 hr after the addition of TRF. TRF did not affect the proliferation of CESS cells and the block of cell proliferation with hydroxyurea did not inhibit the increase of IgG-producing cells, showing that TRF induced IgG-production in CESS cells without any requirement of cell division. TRF activity was completely removed by CESS cells but TCGF-activity in the same preparation was not absorbed with CESS cells. On the other hand, TCGF-dependent human killer cells absorbed TCGF activity but not TRF activity in the same preparation. The binding of 125I-labeled factor(s) on CESS cells was also demonstrated. These results showed the presence of acceptors for TRF on the surface of CESS cells and this cell line will provide useful means for the chemical characterization of acceptors and for the study of the mechanisms of the signal transmission through acceptors.

T cell-replacing factor- (TRF) induced IgG secretion in a human B blastoid cell line and demonstration of acceptors for TRF

IgG-secretion was induced in a human B blastoid cell line, CESS, by the addition of partially purified T cell-derived helper factor(s) (TRF), which had been obtained from PHA-stimulated human T cells. The number of IgG-producing cells in CESS cells reached its maximal level (10% of total cells) within 48 hr after the addition of TRF. TRF did not affect the proliferation of CESS cells and the block of cell proliferation with hydroxyurea did not inhibit the increase of IgG-producing cells, showing that TRF induced IgG-production in CESS cells without any requirement of cell division. TRF activity was completely removed by CESS cells but TCGF-activity in the same preparation was not absorbed with CESS cells. On the other hand, TCGF-dependent human killer cells absorbed TCGF activity but not TRF activity in the same preparation. The binding of 125I-labeled factor(s) on CESS cells was also demonstrated. These results showed the presence of acceptors for TRF on the surface of CESS cells and this cell line will provide useful means for the chemical characterization of acceptors and for the study of the mechanisms of the signal transmission through acceptors.

In vitro immune response of human peripheral lymphocytes. VI. Distribution and characterization of precursors for PHA- and protein A-induced colony-forming B cells

B cells from peripheral blood or cord blood formed colonies by stimulation with either PHA or protein A. On the other hand, tonsillar B cells did not form protein A-induced colonies, although PHA-induced colony formation was comparable to that observed in peripheral B cells. Lack of protein A-induced colony formation in tonsillar B cells was not due to the defect of helper T cells in preculture or to the presence of suppressor cells but was due to the absence of precursors for colony formation. The result showed that PHA- and protein A-induced colony-forming cells belonged to distinct subsets of B cells. Depletion of mu-bearing cells from peripheral B cells abrogated both PHA- and protein A-induced colony formation. Depletion of delta-bearing cells did not affect PHA- and protein A-induced colony formation and the population enriched with delta-bearing cells also showed colony formation. Depletion of complement receptor (CR)-positive cells removed precursors for both PHA- and protein A-induced colony formation. These results showed that precursor cells for PHA- and protein A-induced colony formation were IgM+, IgD+ and CR+ or IgM+, IgD- and CR+.

In vitro immune response of human peripheral lymphocytes. VII. Effect of anti-mu and anti-delta antibodies on B colony formation and detection of abnormal B cells in patients with juvenile rheumatoid arthritis

Effect of anti-mu and anti-delta antibodies on PHA- and protein A-induced B colony formation was studied. Anti-mu antibody at any concentrations tested did not show inhibitory or enhancing effect on colony formation. On the other hand, anti-delta antibody enhanced both PHA- and protein A-induced colony formation. Optimum concentration of anti-delta antibody for maximum enhancement was 0.1 microgram/ml. and F(ab')2 fragment of anti-delta antibody also showed comparable enhancing effect. Simultaneous addition of IgD with anti-delta antibody abrogated anti-delta-induced enhancement, and anti-delta antibody did not show any facilitation of colony formation in IgM+ IgD- cell population. In marked contrast with normal B cells, anti-mu antibody showed a remarkable enhancing effect on protein A-induced colony formation of B cells from JRA patients. F(ab')2 fragment of anti-mu antibody also showed comparable enhancing effect. Anti-mu antibody did not show any enhancement of colony formation of B cells from several other autoimmune diseases. The result indicated the presence of abnormal B cells in JRA patients.

In vitro immune response of human peripheral lymphocytes. VI. Distribution and characterization of precursors for PHA- and protein A-induced colony-forming B cells

B cells from peripheral blood or cord blood formed colonies by stimulation with either PHA or protein A. On the other hand, tonsillar B cells did not form protein A-induced colonies, although PHA-induced colony formation was comparable to that observed in peripheral B cells. Lack of protein A-induced colony formation in tonsillar B cells was not due to the defect of helper T cells in preculture or to the presence of suppressor cells but was due to the absence of precursors for colony formation. The result showed that PHA- and protein A-induced colony-forming cells belonged to distinct subsets of B cells. Depletion of mu-bearing cells from peripheral B cells abrogated both PHA- and protein A-induced colony formation. Depletion of delta-bearing cells did not affect PHA- and protein A-induced colony formation and the population enriched with delta-bearing cells also showed colony formation. Depletion of complement receptor (CR)-positive cells removed precursors for both PHA- and protein A-induced colony formation. These results showed that precursor cells for PHA- and protein A-induced colony formation were IgM+, IgD+ and CR+ or IgM+, IgD- and CR+.

In vitro immune response of human peripheral lymphocytes. VII. Effect of anti-mu and anti-delta antibodies on B colony formation and detection of abnormal B cells in patients with juvenile rheumatoid arthritis

Effect of anti-mu and anti-delta antibodies on PHA- and protein A-induced B colony formation was studied. Anti-mu antibody at any concentrations tested did not show inhibitory or enhancing effect on colony formation. On the other hand, anti-delta antibody enhanced both PHA- and protein A-induced colony formation. Optimum concentration of anti-delta antibody for maximum enhancement was 0.1 microgram/ml. and F(ab')2 fragment of anti-delta antibody also showed comparable enhancing effect. Simultaneous addition of IgD with anti-delta antibody abrogated anti-delta-induced enhancement, and anti-delta antibody did not show any facilitation of colony formation in IgM+ IgD- cell population. In marked contrast with normal B cells, anti-mu antibody showed a remarkable enhancing effect on protein A-induced colony formation of B cells from JRA patients. F(ab')2 fragment of anti-mu antibody also showed comparable enhancing effect. Anti-mu antibody did not show any enhancement of colony formation of B cells from several other autoimmune diseases. The result indicated the presence of abnormal B cells in JRA patients.

In vitro immune response of human peripheral lymphocytes. V. PHA- and protein A-induced human B colony formation and analysis of the subpopulations of B cells

Human B colony formation was observed with PHA or protein A as a mitogen. Preculture of B cells with mitogens in the presence of irradiated T cells for 3 days was a prerequisite for the induction of B cell colonies. About 300 to 700 colonies per 10(6) seeded cells were detected and a linear relationship between the number of cells seeded and the number of colonies developed was observed. Cells in PHA-induced colonies had surface IgM and/or IgD but no cytoplasmic Ig, whereas cells recovered from protein A-induced colonies had cytoplasmic Igs that were not only IgM but IgG and IgA. In each of the protein A-induced colonies, a sequential appearance of IgM-, IgG-, and IgA-producing cells was observed from day 3 to day 5, showing that IgM-, IgG-, and IgA-producing cells were derived from a single precursor cell. PHA and protein A had an additive effect on the number of colonies induced. About 50% of colonies induced in the presence of both PHA and protein A had Ig-producing cells. These results suggest that PHA and protein A may stimulate distinct subsets of B cells into colony formation.

In vitro immune response of human peripheral lymphocytes. V. PHA- and protein A-induced human B colony formation and analysis of the subpopulations of B cells

Human B colony formation was observed with PHA or protein A as a mitogen. Preculture of B cells with mitogens in the presence of irradiated T cells for 3 days was a prerequisite for the induction of B cell colonies. About 300 to 700 colonies per 10(6) seeded cells were detected and a linear relationship between the number of cells seeded and the number of colonies developed was observed. Cells in PHA-induced colonies had surface IgM and/or IgD but no cytoplasmic Ig, whereas cells recovered from protein A-induced colonies had cytoplasmic Igs that were not only IgM but IgG and IgA. In each of the protein A-induced colonies, a sequential appearance of IgM-, IgG-, and IgA-producing cells was observed from day 3 to day 5, showing that IgM-, IgG-, and IgA-producing cells were derived from a single precursor cell. PHA and protein A had an additive effect on the number of colonies induced. About 50% of colonies induced in the presence of both PHA and protein A had Ig-producing cells. These results suggest that PHA and protein A may stimulate distinct subsets of B cells into colony formation.

In vitro induction of IgM secretion and switching to IgG production in human B leukemic cells with the help of T cells

In vitro stimulation of the B leukemic cells (B-CLL cells) with normal allogeneic T cells plus PWM induced IgM secretion and a switching from IgM to IgG production. Induction of IgM and IgG production in B-CLL cells with T cells was demonstrated by the presence of the same idiotype in induced Ig as that present in the monoclonal IgM protein in the patient's serum. Both T cells and PWM were required for Ig induction in B-CLL cells, and x-irradiated T cells showed the comparable helper effect. T cells and PWM induced not only Ig secretion but proliferation of B-CLL cells. Cell division was essential for the differentiation of the leukemic cells to Ig-producing cells. PWM-induced, antigen-nonspecific helper factor(s) were also effective in the induction of differentiation of the leukemic cells. Variations existed among T cell donors in the capabilities to induce differentiation of the same leukemic cells, suggesting the requirement of matching of acceptors on B-CLL cells and T effector molecules for the induction of Ig production in B-CLL cells.

In vitro induction of IgM secretion and switching to IgG production in human B leukemic cells with the help of T cells

In vitro stimulation of the B leukemic cells (B-CLL cells) with normal allogeneic T cells plus PWM induced IgM secretion and a switching from IgM to IgG production. Induction of IgM and IgG production in B-CLL cells with T cells was demonstrated by the presence of the same idiotype in induced Ig as that present in the monoclonal IgM protein in the patient's serum. Both T cells and PWM were required for Ig induction in B-CLL cells, and x-irradiated T cells showed the comparable helper effect. T cells and PWM induced not only Ig secretion but proliferation of B-CLL cells. Cell division was essential for the differentiation of the leukemic cells to Ig-producing cells. PWM-induced, antigen-nonspecific helper factor(s) were also effective in the induction of differentiation of the leukemic cells. Variations existed among T cell donors in the capabilities to induce differentiation of the same leukemic cells, suggesting the requirement of matching of acceptors on B-CLL cells and T effector molecules for the induction of Ig production in B-CLL cells.

In vitro immune response of human peripheral lymphocytes. II. Properties and functions of concanavalin A-induced suppressor T cells

Con A-stimulation of human peripheral T lymphocytes induced both suppressor and helper T cells. ConA-generated suppressor T cells inhibited PWM-induced IgG and IgM production in PBL. Lower concentrations of Con A (0.5 micrograms/ml) or shorter incubation periods (6 to 24 hr) induced mainly helper T cells, while higher concentrations of Con A (10 micrograms/ml) or longer incubation periods (at least 48 hr) induced suppressor T cells. Con A-generated suppressor T cells were sensitive to mitomycin treatment and exerted their suppressor function on the early phase of differentiation and/or proliferation of B cells but not on the final differentiation of B cells to Ig-producing cells. The identity of the MHC was not required for the expression of suppressor function. Suppressor T cells competed with helper T cells in PWM-induced Ig-production of PBL. This experimental system can be applied to estimate the regulatory function of T cells in several disease states.