Functional analysis of murine and human B lymphocyte subsets

Cells and mediators which participate in immunoglobulin synthesis by human mononuclear cells. II. The mechanism of null cell participation in immunoglobulin synthesis and secretion by B cells

Immunoglobulins were synthesized and secreted by human B cells cultured with T cells with receptors for FcM (TM) helper cells, monocytes, null cells and PWM for 7 days. Immunoglobulin synthesis did not take place if the null cells were omitted from the cultures irrespective of the duration of the culture period. Null cells incorporated into the cultures at only 25% of their optimal concentration did not affect immunoglobulin synthesis markedly by the cultured B cells. However, the number of B cells in the culture could not be diluted without an accompanying marked reduction in immunoglobulin synthesis. The B cells synthesized and secreted significant quantities of immunoglobulin even when the null cells were added as late as day 6 of the 7-day culture whereas no or very little immunoglobulin was synthesized if the B cells were not present from the beginning of the 7-day culture. It was demonstrated that cultured null cells do not transform into B cells and do not attain their immunoglobulin-synthesizing function. Furthermore, cultured B cells do not transform into null cells and do not attain their helper function. The null cells can also be distinguished from the B cells on the basis of cell-surface markers, receptors, and blastogenic responsiveness to phytomitogens. It is concluded that (i) the human circulating B cells require the null cells, in addition to the TM cells, monocytes and PWM, in culture in order to synthesize and secrete immunoglobulin; (ii) the null cell signal that stimulates immunoglobulin synthesis and secretion by the B cells is probably the last signal following the TM helper cell, monocyte and PWM signals received by the B cells; and (iii) the null cells and the B cells constitute distinct lineages of cells.

Kinetics of thymidine incorporation into detergent-soluble DNA of mouse lymphocytes

We reported recently that splenocytes from concanavalin A-stimulated mice rapidly incorporated [3H]thymidine into non-mitochondrial DNA that was detergent soluble and distributed in size classes between 200 and 5000 base pairs. In this report we show that small [3H]thymidine-labeled oligonucleotides (less than 100 base pairs long) appear by 15 min. Subsequently, [3H]thymidine in small oligonucleotides diminishes as incorporation into larger size classes of detergent-soluble DNA occurs in a pattern that is stable for at least 3 hr. Although incorporation of [3H]thymidine into the oligonucleotides is not sensitive to aphidicolin or hydroxyurea, the appearance of [3H]thymidine in larger species is blocked by both drugs. These results indicate that the enzymatic process involved in synthesis of oligonucleotides is somehow distinct from the process involved in synthesis of larger detergent-soluble size classes. Synthesis of the latter may be replication related.

T cell-replacing factor for glucocorticosteroid-induced immunoglobulin production. A unique steroid-dependent cytokine

Glucocorticosteroids (GCS) added to otherwise unstimulated cultures of human peripheral blood mononuclear cells (PBMC) induce the synthesis and secretion of all classes of immunoglobulin. The magnitude of this response is similar to that seen with other polyclonal B cell activators such as pokeweed mitogen (PWM), and like that of PWM, the steroid effect is dependent on both T cells and monocytes. To determine the cellular target for GCS in these cultures, separated populations of T cells and non-T cells were preincubated with steroids and then recombined. No immunoglobulin was produced in any of these preincubation experiments. As a different approach to this question, supernatants were collected from various cell populations following stimulation with PWM, concanavalin A (Con A), phytohemagglutinin (PHA), alloantigens, or GCS. These supernatants were tested for their effects on GCS-induced Ig production by B cells. Supernatants from 3-d cultures of unstimulated, as well as GCS-treated, PBMC contained a T cell-replacing factor that permitted T-depleted PBMC to produce Ig upon steroid stimulation. This supernatant factor (TRF-S) could be produced in the absence of steroid stimulation, but both the factor and GCS were necessary for the induction of Ig synthesis. Production of the TRF-S required the presence of both T cells and adherent cells in culture and was found in the highest concentrations at 3-4 d of culture. Supernatants from cultures stimulated with PWM, PHA, Con A, and alloantigens did not contain detectable TRF-S activity, and TRF-S was unable to replace helper T cells for PWM-induced Ig production. TRF-S required the presence of adherent cells in the T cell-depleted responder population for its action. Further, it was effective in inducing Ig production along with GCS in the presence of a sufficient concentration of cyclosporin A to block all T cell helper activity for primary responses of PBMC to PWM or GCS. TRF-S was inactivated by trypsin treatment, heating to 56 degrees C, freezing, lyophilization, and storage at 4 degrees C for greater than 3 wk. Its molecular weight is probably 10,000 daltons or more, since TRF-S activity is not rapidly dialyzable. These experiments indicate that GCS-induced Ig production by human B cells does not require the presence of intact T cells in the cultures and therefore the steroids are not exerting their influence directly on T suppressor or T helper cells. Furthermore, they demonstrate a previously unrecognized cytokine that induces the differentiation of human B cells to Ig production in the presence of GCS.

Monoclonal antibodies against HLA-DR antigens replace T helper cells in activation of B lymphocytes

In the presence but not in the absence of pokeweed mitogen (PWM), monoclonal antibodies against HLA-DR antigens 147 and 164 helped highly purified B lymphocytes to proliferate and mature to Ig-secreting cells. In contrast, neither anti-DR antibody 231 nor the UCHT1 monoclonal anti-human T cell antibody (both of the same isotype as the 147 and 164 anti-DR antibodies) exhibited any helper activity on B cells. B cells pulsed with PWM and subsequently cultured in the presence of anti-DR antibody 147 or 164 proliferated and secreted Ig, whereas B cells that first were pulsed with antibody 147 or 164 and then incubated with PWM did not. PWM alone did not induce any of these responses on purified B cells. Also, antibodies 147 and 164 significantly increased the number of Ig-secreting cells obtained from the WT51 Epstein-Barr virus-transformed B-cell line. Anti-DR antibody 231 inhibited the helper activity on WT51 cells mediated by anti-DR antibody 164. Finally, anti-DR antibodies 147 and 164 assisted B cells from the spleen of athymic nu/nu mice (which bear I-E-encoded products) to produce IgM antibodies against sheep erythrocytes. However, these antibodies had no effect on mouse B cells which do not express on their surface I-E-encoded Ia antigens. Taken collectively, these findings suggest that the structures detected by anti-DR antibodies 147 and 164 on B lymphocytes function as acceptors/transducers of T-cell-derived helper signals.

Loss of secretion in mouse-human hybrids need not be due to the loss of a structural gene

Three cloned mouse-human lines (B1-29, E2-42, and A2-31) secreting human immunoglobulin (Ig) were obtained from a fusion between the mouse myeloma line NS-1 and human tonsillar lymphocytes stimulated in vitro with pokeweed mitogen. One line, B1-29, has continued to secrete human IgG for a period of 2 yr in culture. This line was recloned three times to give a panel of secreting and nonsecreting subclones. Most of the nonsecreting subclones had also lost surface Ig. The structural genes for human Ig heavy chains have been provisionally assigned to chromosome 14, which also encodes the enzyme nucleoside phosphorylase. Human nucleoside phosphorylase was detected in all secreting and nonsecreting B1-29 subclones, indicating the presence of human chromosome 14. The retention of chromosome 14 in nonsecreting clones implied that the structural genes for human Ig were A2-31 and E2-42, which had stopped secreting, an attempt was made to restimulate the secreting of human Ig with mitogens A2-31 was unique among the cell lines examined, in that chromosome 14 could not be detected by an isoenzyme marker. Lipopolysaccharide, at an optimum dose of 10 micrograms/ml, restimulated these nonsecreting hybrid lines to secrete human IgG in levels up to 0.7 micrograms/ml. Loss of Ig secretion may not therefore be caused by loss of Ig structural genes.

Comparison of the induction of immunoglobulin M and G antibodies in mice with purified pneumococcal type 3 and meningococcal group C polysaccharides and their protein conjugates

The nature and kinetics of the serum antibody response to pneumococcal type 3 and meningococcal group C polysaccharides and their protein conjugates were studied in mice. Bovine serum albumin and diphtheria and tetanus toxoids were used as carrier proteins. The purified polysaccharides induced only immunoglobulin M (IgM) antibodies in thymus-bearing as well as congenic athymic (nude) mice. The polysaccharides covalently conjugated to proteins produced IgM and IgG antibodies in normal mice, but only IgM antibodies in nude mice. A second dose of the polysaccharide-protein conjugates resulted in a booster effect in the IgG response to the polysaccharides. Moreover, memory B-cells, generated after a primary injection with the polysaccharide-protein conjugates, could be triggered to the production of IgG antibodies after a second injection with the pure polysaccharides alone. These data indicate that the antibody response to the pure polysaccharides is thymus independent and that this response can be changed into a thymus-dependent response by covalent conjugation of the polysaccharide to a thymus-dependent protein.

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.

Tumor promoter phorbol myristic acetate stimulates immunoglobulin secretion correlated with growth cessation in human B lymphocyte cell lines

Immunoglobulin production by lymphoblast cell lines was studies using protein A-red blood cell plaque formation to detect individual secreting cells. Immunoglobulin (Ig) secretion by 6 of 12 human B-cell lines tested could be stimulated up to twentyfold by phorbol myristic acetate (PMA) at subtoxic concentrations of 10-1000 ng/ml depending on the line. Stimulation was found with both IgM and IgG cell lines. No switch of Ig class synthesis was found in the cell lines as a result of PMA incubation. Increase in Ig secretion was closely associated with cessation of growth resembling induction of terminal differentiation in the cells. PMA induction of Ig secretion in B lymphocytes from normal peripheral blood requires the cooperation of T cells. PMA stimulation of certain cell lines reported here suggests that the lines are late in the differentiation pathway to plasmacyte and can be easily triggered to secrete Ig by membrane-altering agents.

Polyclonal activation of human B lymphocytes by Fc fragments. I. Characterization of the cellular requirements for Fc fragment-mediated polyclonal antibody secretion by human peripheral blood B lymphocytes

Fc fragments derived from human immunoglobulin were found to be capable of inducing both a proliferative and polyclonal antibody response in human peripheral blood lymphocyte cultures. The cell population proliferating in response to Fc fragments belongs to the B cell lineage. Expression of polyclonal antibody formation requires the presence of both adherent monocytes and T cells. The role of the monocyte is to enzymatically cleave the Fc fragment into 19,000 mol wt Fc subfragments that are then able to induce polyclonal antibody secretion. Stimulation of polyclonal antibody production by Fc subfragments occurs in the absence of adherent monocytes but still requires the presence of T cells.

Expression of cell surface markers after human B lymphocyte activation

The fate of two recently described human B lymphocyte-specific antigens (B1 and B2) was studied after B-cell activation in vivo and in vitro. Whereas both B1 and B2 were present on virtually all B cells from normal lymph nodes, B2 was absent from approximately 50% of B cells from hyperplastic lymph nodes. When B cells from spleen, tonsil, or peripheral blood were stimulated in vitro with pokeweed mitogen, activated cells were found to lose B2 (days 4-5) and subsequently B1 (days 6-7). Temporally, B2 loss was accompanied by loss of surface IgD, expression of T10, and the development of intracytoplasmic IgM; B1 loss was correlated with the acquisition of surface IgG and the appearance of intracytoplasmic IgG. Peripheral blood B cells, on which B2 is normally only weakly expressed (B1++++B2+) in contrast to B cells from secondary lymphoid organs (B1++++B2++), exhibited a transitory increase in B2 expression to the B1++++B2++ phenotype prior to B2 disappearance during activation. Taken together with other findings, this observation suggests that peripheral blood may contain a relatively immature subpopulation of B cells.

Polyclonal activation of human peripheral blood B lymphocytes by formaldehyde-fixed Salmonella paratyphi B. I. Immunoglobulin production without DNA synthesis

A "new" polyclonal activator of human peripheral blood B cells, formaldehyde-fixed Salmonella paratyphi B, is described. This bacterium does not stimulate cell proliferation as measured by incorporation of tritiated thymidine but does stimulate a subpopulation of B cells to secrete large amounts of IgM, IgG, and IgA in 7-day cell cultures. The immunoglobulins (Ig) produced by cells responding to S. paratyphi B are not specific antibodies against the bacterial antigens. In comparison with other B cell activators (pokeweed mitogen, Staphylococcus aureus Cowan I, and lipopolysaccharide), S. paratyphi B stimulation produced greater amounts of IgM but less IgG than pokeweed mitogen (PWM) or S. aureus Cowan I; lipopolysaccharide failed to stimulate significant Ig production on day 7 in most cases. In addition, the response to S. paratyphi apparently did not require T cell collaboration. These results suggest that the B cell subpopulation(s) responding to S. paratyphi B may be more differentiated B cells than those responding to either PWM or S. aureus Cowan I. Peripheral blood mononuclear cells from five patients with common variable immunodeficiency without evidence of abnormal suppressor T cells or monocytes failed to respond to S. paratyphi B, whereas cells from two of the same patients responded well to S. aureus Cowan I and partially to PWM. Thus, S. paratyphi B appears to be superior to other B cell activators for studies of B cell function in normal and abnormal states.

B cell differentiation and immunoregulatory T cell function in human cord blood lymphocytes

The functional maturity of T and B lymphocyte populations from human newborns was evaluated using a reverse hemolytic plaque assay to detect immunoglobulin-secreting cells generated in in vitro cultures stimulated with pokeweed mitogen (PWM), a T cell-dependent polyclonal activator, and the Epstein-Barr virus (EBV), a T cell-independent B cell activator. Cord blood lymphocytes failed to produce immunoglobulin in response to PWM, but did respond with immunoglobulin synthesis to stimulation with EBV. Co-culture experiments demonstrated that cord blood T cells would inhibit immunoglobulin production by adult cells stimulated with PWM, but not with EBV. Cord blood T cells did suppress immunoglobulin production by cord blood B cells when stimulated with a mixture of EBV and PWM, indicating that cord blood, in contrast to adult blood, contains a population of suppressor T cell precursors that are easily activated by PWM. Irradiation of the cord blood T cells with 2,000 rad eliminated the suppressor activity and revealed normal helper function for immunoglobulin (Ig) G, A, and M when these T cells were co-cultured with adult B cells. Cord blood B cells co-cultured with adult T cells or irradiated cord blood T cells did produce immunoglobulin in response to PWM, but the response was significantly lower than that of adult B cells, and only IgM was produced in these cultures. These studies demonstrate that both the T and B cells of the human newborn have significant functional differences compared with the functions of T and B lymphocyte populations in adults.

The primary immune response of patients with different stages of squamous-cell bronchial carcinoma

Using the indirect ELISA technique, the IgM, IgG, and IgA antibody response to the primary test immunogen Helix pomatia haemocyanin (HPH) was studied in 30 patients with various clinical stages of primary squamous-cell bronchial carcinoma and compared with values obtained in 15 controls matched for sex, age, smoking habit, and presence of chronic bronchitis. Patients with disseminated disease (stage III) showed a significant decrease in IgG and IgA antibody response (P less than 0.001), but IgM antibodies were relatively high and not different from the controls. Although normal IgG and IgA antibody titres were found at the peak response two weeks after immunisation in patients with localised disease (stage I), these antibody titres showed a significantly more rapid decline after serial investigations at eight and 14 weeks after immunisation compared with the controls (P less than 0.001) despite total removal of the tumour burden at c four weeks after immunisation. In-vitro HPH-induced lymphocyte transformation was considerably decreased in state I patients (P less than 0.01) as well as in stage III patients (P less than 0.001). The results suggest that patients with squamous-cell bronchial carcinoma develop impaired T-cell function, which gives rise to a defective antibody response and in-vitro lymphocyte reactivity to the T-cell dependent primary immunogen HPH.

Cytochalasin B-induced changes in concanavalin A-activated lymphocytes

Cytochalasin B (CB) administered simultaneously with a mitogenic dose of concanavalin A (Con A) interferes with the activation process. This interference involves structural alterations of cellular membrane which do not include a reduced Con-A-binding capacity. This conclusion is supported by the observation of deformities in both nuclear and cytoplasmic membranes in Con A-activated lymphocytes subsequently treated with CB. The high incidence of membrane blebs and pseudomyelin bodies in the cytoplasm points to a general effect of CB on the structural organization of membrane which may secondarily interfere with some specific event such as generation or transfer of signals for activation or cytokinesis.

Studies in porphyria. VII. Induction of uroporphyrinogen-I synthase and expression of the gene defect of acute intermittent porphyria in mitogen-stimulated human lymphocytes

A 50% reduction in the activity of uroporphyrinogen-I (URO) synthase in liver, erythrocytes, and cultured skin fibroblasts characterizes all patients with clinically active acute intermittent porphyria (AIP). The same enzyme defect has also been demonstrated in the erythrocytes and skin fibroblasts of completely latent gene carriers of this disorder and presumably exists in the liver as well. In this study, we examined whether or not the formation of URO-synthase is impaired in AIP cells using lymphocytes treated with mitogens or infected with Epstein-Barr virus. Both mitogens (phytohemagglutinin and pokeweed mitogen) and Epstein-Barr virus induced the synthesis of URO-synthase in lymphocytes, but the induction of URO-synthase in AIP lymphocytes was only 50% as compared with that in normal lymphocytes. The impaired induction of URO-synthase in AIP lymphocytes reflects a specific gene defect because AIP lymphocytes showed normal [(3)H] thymidine uptake into DNA, [(3)H] uridine uptake into RNA, and normal delta-aminolevulinic acid (ALA) synthase, ALA-dehydratase, catalase activities, and heme content. Utilizing the same methodology, the ferrochelatase deficiency of hereditary erythropoietic protoporphyria could also be identified. The K(m) of the induced URO-synthase in AIP cells was identical to that of the enzyme in normal cells. The induced URO-synthase of mitogen-treated AIP lymphocytes was not accompanied by a concurrent enhanced level of ALA-synthase. Moreover, the URO-synthase deficiency in lymphocytes from actively ill AIP patients was not different from the level of enzyme activity when they were in clinical remission, or when compared with the enzyme activity of cells from completely latent AIP gene carriers. The results of this study indicate that the URO-synthase deficiency in AIP may be the result of a gene mutation regulating the rate of synthesis of a normal enzyme rather than a mutation causing a structural abnormality of this enzyme protein.

Regulation of the induction of colonies in vitro by normal human lymphocytes

Lymphocytes isolated from normal human peripheral blood can be induced to form colonies in vitro by incubation with the appropriate inducer. Phytohemagglutinin can induce colonies with T (thymus-derived) lymphocytes. Optimun colony formation with about two colonies per 10(2) peripheral blood lymphocytes was obtained by adding, in addition to phytohemagglutinin, autologous plasma, autoologous red blood cells, and fresh L-glutamine or L-cystine. In the absence of these fresh amino acids, no colonies were formed at seeding levels below 10(5) cells per 35 mm petri dish. The addition of either of these amino acids gave a 10-fold decrease in the minimum number of cells that had to be seeded for colony formation. Lipopolysaccharide did not induce the formation of colonies, but enhanced the formation of T cell colonies by phytohemagglutinin. The mixing of lymphocytes from persons with and deficient in glucose-6-phosphate-dehydrogenase (EC 1-1-1-49) has shown that phytohemagglutinin-induced colonies can be derived from single cells and are, therefore, clones. No colonies were formed by lethally irradiated cells. Incubation with pokeweed mitogen also induced the formation of colonies. With autologous plasma and autologous red blood cells, pokeweek mitogen induced about one colony per 5 X 10(3) cells seeded and no colonies at seeding levels below 10(5) cells per petri dish. The minimum number of cells needed for colony formation by pokeweed mitogen was not decreased by fresh L-glutamine or L-cystine. The results indicate that normal human lymphocytes can be cloned in vitro and that induction of these lymphocyte colonies can be regulated by lectins and other specific factors.

Polyclonal activation of bone-marrow-derived lymphocytes from human peripheral blood measured by a direct plaque-forming cell assay

A culture and assay system for the stimulation of human peripheral blood lymphocytes with polyclonal activators of bone-marrow-derived lymphocytes (B cells), such as pokeweed mitogen and Escherichia coli lipopolysaccharide, and subsequent measurement of single cell antibody production by a hemolysis-in-bel direct plaque-forming cell assay against sheep erythrocytes has been established. The critical culture requirements have been delineated and a new highly sensitive ultrathin gel assay method has been described. Under these conditions a substantial and highly reproducible plaque-forming cell response was detected in normal human peripheral blood. This system can be readily used to explore the complex events associated with activation of human B cells.

Induction of IgG in young nude mice by lipid A or thymus grafts

Postnatal serum concentrations of IgG2a of paternal allotype, measured in congenitally thymusless nude mice, increase with kinetics and titers comparable to their normal congeneic counterparts. Lipid A, the mitogenic part of LPS, stimulates IgG synthesis in nude mice when it is given 7 days after birth. IgG concentrations at 15 days of age are 6- to 8-fold higher than in untreated control nudes; this is considerably lower, however, than in normal mice, which show up to 45-fold higher IgG2ab levels after lipid A treatment. A thymus graft from nearly congeneic donors of the same age, transplanted at 4 days after birth, also stimulates long-lasting IgG synthesis in the nude recipients. If the grafted nudes are injected with lipid A 3 days later, IgG synthesis is further stimulated 8- to 16-fold. The data are discussed in relation to the thymus dependency of IgG production and the conditions for lipid A stimulation.

Activation of human B lymphocytes. I. Direct plaque-forming cell assay for the measurement of polyclonal activation and antigenic stimulation of human B lymphocytes

A model for the detection of single cell antibody production by human tonsillar lymphocytes after stimulation with either sheep red blood cells (SRBC) or polyclonal B-cell activators has been described. The culture system is a modified Mishell-Dutton technique with certain critical factors identified. The assay is a sensitive and resproducible hemolysis-in-gel system employing an ultra-thin layer gel technique measuring plaque-forming cells (PFC) against SRBC targets. Several factors essential for optimal responses are described, but the critical feature of the culture system is the use of selected lots of human AB serum supplements which are extensively absorbed with SRBC. This removes a blocking factor present in most human serum which suppresses the B-cell response to SRBC targets after stimulation with either SRBC or several polyclonal B-cell activators. In addition, absorption of serum with SRBC eliminates the presence of artifactual plaques. Background PFC are extremely low and stimulated cultures show significant and reproducible responses. These studies provide a simple, sensitive, and reproducible model for probing the complex events associated with activation of human B lymphocytes.