Human B cell function in a polyclonally induced plaque forming cell system. Cell triggering and immunoregulation

Higher proliferative response in B-chronic lymphocytic leukemia (B-CLL) as compared to B-monoclonal lymphocytosis of undetermined significance (B-MLUS) after stimulation with Staphylococcus aureus and anti-CD40 monoclonal antibodies

B-CLL is a malignant monoclonal B-cell disorder and B-MLUS is the benign counterpart. The proliferative response and the capacity to secrete IgM was measured in B-CLL and B-MLUS, respectively, and compared to normal B-cells. SAC and a mAb against CD40 were used as stimulatory agents. No cell population responded to anti-CD40 mAb alone. SAC only induced a high DNA synthesis rate in normal B-cells as well as in B-CLL cells, although the magnitude was three-fold lower and delayed for about 48 h in B-CLL. B-MLUS cells did not proliferate in response to SAC. The combination of anti-CD40 and SAC enhanced the proliferative capacity of normal B-cells and produced a more rapid response in B-CLL. B-MLUS cells were not activated. Normal B-cells and B-MLUS did not secrete IgM after SAC stimulation, while B-CLL cells had a continuous increase in the IgM production during a 6-day culture period. The higher proliferative capacity of B-CLL cells compared with B-MLUS cells may be explained by an increased expression of activation molecules e.g. receptors for various cytokines and growth factors. Moreover, the inertness and inability of B-MLUS cells in comparison to normal B- and B-CLL cells to respond to powerful activation signals might indicate an intrinsic defect of B-MLUS cells in the signal transduction leading to a block of mitosis and a benign course of the disease.

Defective T lymphocyte function in nonthymectomized patients with myasthenia gravis

In vitro functional properties of peripheral blood mononuclear cells were evaluated in 29 patients with myasthenia gravis and in 11 healthy controls. Spontaneous cell proliferation was higher in patients than in controls. The production of interleukin-2 and interferon-gamma and the proliferative response to different mitogens were reduced in the patients. A positive correlation was found between the production of interleukin-2 and interferon-gamma. These defects in T cell function were the most pronounced in nonthymectomized patients. Patients with severe disease had a higher percentage of cells bearing the interleukin-2 receptor and a higher spontaneous production of tumor necrosis factor alpha in cell culture than in patients with mild disease. There was no difference between patients and controls in the level of soluble interleukin-2 receptor in cell culture supernatants or in sera. The results indicate a partially suppressed T cell function in myasthenia gravis. This defect was less pronounced in patients studied after thymectomy.

In vitro ozone exposure inhibits mitogen-induced lymphocyte proliferation and IL-2 production

Human blood mononuclear cells were exposed to ozone in vitro and thereafter analyzed for competence in mitogen-induced proliferation as well as IL-1 and IL-2 production. Proliferative responses induced by phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) were all depressed in lymphocytes exposed to an ozone concentration of 1 ppm for 4-6 h. The response to PWM was most sensitive to the ozone effect (38% suppression); responses to Con A and PHA were suppressed to a lesser extent, 23% and 18%, respectively, and were not significantly different from each other. PWM responses were affected at an ozone concentration as low as 0.1 ppm; however, no suppression of Con A-induced proliferation was seen below 0.18 ppm or of PHA-induced proliferation below 0.5 ppm. When lymphocytes and monocytes were exposed separately to ozone and then mixed back with control air-exposed monocytes or lymphocytes, both cell types appeared to be affected and the functional defects caused by the pollutant were additive. Monocyte IL-1 production induced by endotoxin was not affected by ozone exposure, while surface expression of HLA-DR on exposed monocytes was reduced by 40% 24 h after exposure. Moreover, lymphocytes exposed to ozone produced 46% less IL-2 while expressing similar surface density of IL-2 receptors. Taken together, these results show that exposure to ozone has distinct adverse effects on lymphocytes and monocytes, both of which are important in local immune defenses in the lung.

Induction of human B cell differentiation by Fc region activators. I. Identification of an active tetrapeptide

Addition of pFc' fragments, composed of residues 334 to 446 in the Fc region of human IgG1, to cultures of human peripheral blood mononuclear cells resulted in the induction of Ig-secreting cells (ISC). Intact IgG1 and F(ab')2 fragments were inactive. The synthetic peptide p23, representing residues 335 to 357, retained the ISC-inducing property of pFc' fragments. The ISC response to p23 exhibited the isotype pattern IgMSC greater than IgGSC greater than or equal to IgASC. Results from cell depletion experiments revealed that the B cell response to p23 was T cell dependent but relatively monocyte independent. Cell proliferation was not increased in p23-stimulated PBMC cultures. Overlapping synthetic peptides based on the sequence of p23 were used to localize the active site in this molecule. These studies revealed that LPPSR (residues 351 to 355) was the sequence responsible for the ISC-inducing property of p23; however, expression of activity by this pentapeptide sequence could be dampened by N-flanking sequences. Finally, residue-deleted analogs of LPPSR were used to determine that LPPS was the minimum sequence retaining activity. Collectively, these data suggest that the fragmentation of IgG results in the expression of a tetrapeptide sequence with lymphocyte-stimulating properties.

Differentiation of human B lymphocyte subpopulations induced by an alloreactive helper T-cell clone

We have used cloned alloreactive helper T cells to determine if direct T cell-B cell interaction can induce differentiation of human peripheral blood B cells which do not respond to pokeweed mitogen (PWM). T-cell clone 2F8 was derived from a one-way mixed lymphocyte reaction. 2F8 cells are T3+T4+T8-IL-2R+ and proliferate in response to irradiated stimulator cells, but not autologous cells, in the absence of exogenous interleukin-2. 2F8 cells provide allospecific help for polyclonal proliferation and differentiation of B cells in the absence of any other stimulus. The magnitude of this response is comparable to that of the response of the same B cells to PWM and fresh autologous T cells. 2F8 cells could also provide nonspecific help for unrelated donor B cells in the presence of PWM, with no requirement for costimulation by irradiated stimulator cells. Allospecific stimulation of B cells was completely inhibited by antibodies to class II major histocompatibility complex (MHC) framework determinants and was abrogated by 1000-rad irradiation. Cloned 2F8 T cells stimulated differentiation of both small, high-density B cells and larger B cells, generating up to 30% plasma cells with either fraction. B cells forming rosettes with mouse erythrocytes were also induced to differentiate by the helper T cell clone. As found previously, neither small, high-density B cells nor mouse rosette+ B cells responded well to PWM. Direct interaction with allospecific T cells induces differentiation of a broader spectrum of B cells than soluble growth and differentiation factors in conjunction with polyclonal activators such as PWM and protein A containing staphylococci.

Morphological differentiation of human lymphocyte subpopulations following polyclonal stimulation with bacteria and lectin

Mononuclear cells (MNC) were stimulated with different heat-treated gram-positive and -negative bacteria, and the lymphocyte subpopulation interaction, the proliferative response, and the immunoglobulin secretion were analyzed. It can be demonstrated that beta haemolytic streptococci and Staphylococcus aureus have a similar stimulation pattern: early stimulation of helper T cells, cell contacts of helper T cells and B cells, maximum proliferation on day 5 and 7, and Ig secretion peak on day 7. Klebsiella pneumoniae and Yersinia enterocolitica do not cause proliferation, while Ig secretion is seen on day 5. No cell contacts and no T cell stimulation are seen in the Klebsiella culture, whilst Yersinia causes slight helper T cell activation. In contrast, PHA induces strong T cell stimulation, proliferation and expansion of the suppressor T cell subpopulation. Leu 7-positive lymphocytes are not activated by any of these stimulants.

Neuroleukin: a lymphokine product of lectin-stimulated T cells

Neuroleukin is a lymphokine product of lectin-stimulated T cells that induces immunoglobulin secretion by cultured human peripheral blood mononuclear cells. Neuroleukin acts early in the in vitro response that leads to formation of antibody-secreting cells, but continued production of immunoglobulin by differentiated antibody-secreting cells is neuroleukin-independent. Although the factor is not directly mitogenic, cellular proliferation is a late component of the response to neuroleukin. Neuroleukin does not have B-cell growth factor (BCGF) or B-cell differentiation factor (BCDF) activity in defined assays. Neuroleukin-evoked induction of immunoglobulin secretion is both monocyte- and T-cell-dependent.

Electronmicroscopical observations on monocyte-lymphocyte interactions upon stimulation with pokeweed mitogen latex conjugate

In this study we report on the preparation and application of pokeweed mitogen (PWM) conjugated to latex particles. This conjugate (PWM-latex) was prepared by incubation of PWM with latex particles in the presence of glutaraldehyde. The effect of the addition of PWM-latex to human peripheral blood mononuclear cells (PBMC) was fully comparable to the addition of PWM alone i.e. differentiation of lymphocytes into blast cells followed by proliferation of these blast cells as measured by DNA synthesis and total cell number. Electronmicroscopically PWM-latex was found to be taken up by monocytes within the first 24 h after addition. Although no direct interaction could be observed between PWM-latex and lymphocytes, the latter were found to differentiate into blast cells. Due to interactions of these blast cells with latex-containing monocytes, latex particles were obviously released from the phagocytes and close contacts between latex particles and blast cells were regularly seen. In addition, it was found that blast cells of T cell origin, as judged by their positive reaction with anti-T cell monoclonal antibodies, had taken up latex particles. Based on enzyme-cytochemical, functional and light microscopical studies, monocytes could not be detected in the PWM-latex-driven PBMC stimulation after 6 days. At the electronmicroscopical level evidence was found that the inability to demonstrate macrophages could be due to the release of the lysosomal enzyme content and of parts of the cytoplasm.

Functional analysis of pokeweed mitogen-dependent cell interactions in murine spleen cells. I. Lack of B-cell mitogenicity and low frequency of effector helper T cells

The nature of lymphocyte responses on addition of pokeweed mitogen (PWM) to normal murine spleen cells was studied in low cell density cultures. PWM, over a wide range of concentrations, stimulated proliferation in a set of cells roughly 10-fold smaller than the lymphocyte populations responding to either concanavalin A or lipopolysaccharide. PWM also induced a relatively small number of B lymphocytes in these cultures to mature to Ig-secreting plaque-forming cells (PFC). Proliferative and PFC responses were completely abrogated by T-cell removal from normal spleen cell cultures. Moreover, cell mixture and irradiation experiments demonstrated that B lymphocytes do not proliferate in response to PWM, even in the presence of an excess of normal T cells, suggesting that PFC development results from terminal maturation without proliferation. Finally, parallel titrations of cloned helper cells, normal splenic T cells or T-cell blasts induced by PWM showed that the poor B-lymphocyte responses in normal spleen cell cultures is due to the very low frequency of competent helper cells in these populations. PWM, however, was competent to activate and expand this set of helper lymphocytes in primary cultures.

Soluble factors inhibitory for T-cell-dependent immune responses in patients with the acquired immune deficiency syndrome and its prodromes

Supernatants from PBMC obtained from certain patients with AIDS or its prodrome were capable of depressing pokeweed mitogen-driven immunoglobulin production and the proliferative response of T cells to specific antigen. These soluble suppressor factors (SSF) were present in uniquely high concentrations, and were the product of an interaction of T lymphocytes with adherent cells. T-cell independent functions were not modified by soluble suppressor factors. Restoration of immunoglobulin synthesis in SSF-treated cultures was realized by addition of reducing agents such as 2-mercaptoethanol, suggesting inhibitory mechanisms possibly related to that of Con A-induced soluble immune response suppression, and perhaps offering clues to clinically applicable substances capable of modifying such responses. A relationship between SSF-AIDS and a human retrovirus LAV/HTLV III, linked etiologically to AIDS and its prodromes, is suggested by studies of SSF-like substances released by human T-T cell hybridomas derived from LAV+ patients.

T-cell subsets in multiple sclerosis: a comparative study between cell surface antigens and function

Pokeweed mitogen (PWM)-driven immunoglobulin synthesis (IgG, IgA, IgM) and concanavalin A (Con A)-stimulated suppression of allogeneic mixed leukocyte reaction (MLR) were studied and compared to T-cell subsets defined by monoclonal antibodies OKT4 and OKT8 in patients with multiple sclerosis (MS). The group of patients with active progressive MS showed diminished suppressor activity as measured by T-cell functional tests and also an elevated OKT4/OKT8 ratio. The group of MS patients in remission did not show these abnormalities. However, this correlation between functional tests and T-cell phenotypes was not found when separate individuals were considered within the subgroups of MS. Since neither OKT4 nor OKT8-reactive cells represent homogeneous functional subsets of T cells, the OKT4/OKT8 ratio does not account for the functional immunological status of separate individuals but rather provides a global evaluation of T-cell subset disturbances in different groups of diseases.

Detection of IgG in supernatants of pokeweed mitogen-stimulated human lymphocyte cultures by one step solid-phase radioimmunoassay (SPRIA)

A one step solid phase radioimmunoassay is used as a simple and reproducible method of detection and quantitation of IgG produced by human PBL after stimulation with PWM. Modifications of culture conditions are necessary to make culture supernatants suitable for this assay. Pulsing with PWM must be performed in serum-supplemented culture medium for 4-5 days. After thorough washing, medium is then replaced with serum-free medium. Under these conditions, synthesis and secretion of IgG continues for at least 9 days. The amount of IgG produced by 10(6) normal adult PBL as detected in this system is 0.77 +/- 0.47 micrograms. No close correlation between cell proliferation and IgG synthesis was observed.

Soluble suppressor factors in patients with acquired immune deficiency syndrome and its prodrome. Elaboration in vitro by T lymphocyte-adherent cell interactions

Supernatants from peripheral blood mononuclear cells obtained from certain patients with the acquired immune deficiency syndrome (AIDS) or its prodrome were capable of depressing spontaneous and pokeweed mitogen-driven B lymphocyte differentiation into plasmacytes, and the proliferative responses of T cells to specific antigen. These soluble suppressor factors (SSF) were present in uniquely high concentrations, with significant differences from healthy controls and from patients with various other conditions previously associated with factor-mediated immunosuppression. T cell-independent functions were not modified by SSF. Suppression was not genetically constrained, and did not appear to be mediated by cytotoxicity, prostaglandin, or alpha or gamma interferons. SSF was a product of the interaction of T lymphocytes with adherent cells. T cells or T cell factors from AIDS patients, but not from normal controls, could collaborate with control adherent cells in the formation of SSF. Restoration of DNA synthesis-independent differentiation of B lymphocytes into plasmacytes in SSF-treated cultures was realized by addition of reducing agents, such as 2-mercaptoethanol, on culture initiation. These data suggest inhibitory mechanisms possibly related to that of concanavalin A-induced soluble immune response suppression, and perhaps offer clues to clinically applicable substances which are potentially capable of mitigating such responses.

Nonspecific induction of immunoglobulin M antibodies to periodontal disease-associated microorganisms after polyclonal human B-lymphocyte activation by Fusobacterium nucleatum

The production of antibodies to oral bacteria was determined in lymphocyte cultures stimulated with sonicated Fusobacterium nucleatum, a potent inducer of polyclonal B-cell activation. After 9 days the cultures were examined by a microenzyme-linked immunosorbent assay for immunoglobulin M (IgM) antibodies to F. nucleatum, Bacteroides gingivalis, Actinomyces viscosus, and Streptococcus sanguis. Antibodies to these four bacteria were detected in cultures stimulated with polyclonal B-cell activation-inducing concentrations of F. nucleatum. However, significant concentrations of antibodies to F. nucleatum, but not to the other three microorganisms, were produced in cultures that received suboptimal polyclonal B-cell activation-inducing doses of F. nucleatum. Absorption studies indicated the specificity of the antibodies to each of the bacteria tested. IgM antibody production induced by F. nucleatum was enhanced by the addition of T cells. The production of IgM antibodies to the bacteria was reproducible in cultures from a single person tested on 3 consecutive days. The concentration of antibodies in replicate cultures, however, fluctuated greatly. To obtain consistent responses on successive days, multiple replicate cultures were required. These results suggest that F. nucleatum, which is frequently present in subgingival plaque, could induce the production of antibodies not only to F. nucleatum, but also to other microorganisms associated with periodontal diseases.

Suppression of B lymphocytes in mature newborn infants

The ability of cord blood lymphocytes to secrete immunoglobulins during in vitro culture was investigated by means of a reverse hemolytic plaque forming cell (PFC) assay. Mononuclear cord blood cells did not differentiate into immunoglobulin-secreting cells after stimulation with the polyclonal B lymphocyte activator pokeweed mitogen (PWM), contrary to the findings in normal adults. Mononuclear cord blood cells were then separated into T-enriched and T-depleted blood lymphocyte subsets. When these were co-cultured, the PWM-induced immunoglobulin secretion was still low; following irradiation of the T-enriched cells, the numbers of IgM-PFC but not of IgG- or IgA-PFC increased considerably. The effect of irradiation of the T-enriched cells on the PWM-induced IgM response was dose-dependent, with maximal effect at 2500 rad. It is concluded that the low PWM responses obtained using cord blood lymphocytes are in part due to suppression by radiosensitive T suppressor cells. Following removal of this suppression by means of irradiation, B lymphocytes can be induced to secrete IgM, but not IgG or IgA.

Immunosuppressive actions of gold salts

In rheumatoid arthritis both lymphocyte-mediated and antibody-mediated immune reactions are important for the inflammatory lesions. In vivo activated B lymphocytes/plasma cells, T lymphocytes and monocytes/macrophages (Mo) are intimately involved in the disease process. Several clinical observations suggest an immunosuppressive action of gold salts. In humans, gold salts interfere with a number of Mo functions in vitro, including cellular interactions between Mo and T lymphocytes. Some workers have shown that the activation of human T lymphocytes is inhibited by gold salts, most probably secondary to an inhibition of Mo-T cell cooperation. Recent experiments indicate that gold salts also affect the in vitro differentiation of human B lymphocytes in response to polyclonal activators. Both the gold atom and the SH group seem to be important for the immunosuppressive actions of gold salts.

Polyclonal and antigen-specific B-cell responses in patients with common variable immunodeficiency

Antigen-specific antibody responses were investigated in 32 hypogammaglobulinemic patients with common variable immunodeficiency following in vitro sensitization of their peripheral blood lymphocyte cultures with sheep red blood-cell determinants. Anti-sheep red blood-cell antibody-secreting cells were quantitated in a hemolytic plaque assay. Amplification of T-cell help was achieved with the use of the T-cell mitogen concanavalin A or allogeneic irradiated T cells. Four patients groups, A through D, were identified. Group A was comprised of 10 patients whose cultured lymphocyte readily developed into antibody secreting cells. Cultures of 9 patients (Group B) responded suboptimally, but were enhanced following mitogen activation of autologous or exogenous T cells, and those of 7 patients (Group C) responded only when help was amplified. In 7 patients (Group D), no responses were elicited. On the simultaneous assessment of pokeweed mitogen-driven polyclonal generation of immunoglobulin-secreting cells, only 10 responders, all from groups A and B, were identified. Our observations indicate that the majority of patients with common variable immunodeficiency possesses B cells capable of producing antibody in vitro. The ability of some patients' B cells to respond only in the antigen-specific assay while failing to do so in pokeweed mitogen-stimulated cultures suggests that these two reactions are not identical in their activation pathways.

Polyclonal activation of human peripheral blood B lymphocytes by formaldehyde-fixed Salmonella paratyphi B. II. Heterogeneity of B lymphocytes

B-cell 'activation' in cultures stimulated with pokeweed mitogen (PWM), Staphylococcus aureus strain Cowan I, or formaldehyde-fixed Salmonella paratyphi B (SPB) was evaluated by enumeration of cells secreting immunoglobulin (Ig) and by quantitation of Ig released into culture supernatants. A dissociation between these two values was found after day 6 in cultures activated with PWM or SPB, suggesting that Ig-secreting cells (ISC) are heterogeneous in terms of Ig secretion rate. Generation of ISC in cultures activated with PWM or SPB was partially inhibited by hydroxyurea, but Ig levels in culture supernatants were not affected. These results indicate that there are at least two subpopulations of ISC in stimulated peripheral blood lymphocyte cultures, one sensitive to, and the other resistant to, hydroxyurea. The hydroxyurea-resistant subpopulation appeared to be more mature and to release most all of the Ig detected in culture supernatants. Furthermore, time-course studies of ISC numbers and Ig levels showed that each ISC in SPB-stimulated cultures (but not in PWM-stimulated cultures) was more active in Ig synthesis and secretion after day 8 than before day 6, indicating that after day 8 most of the ISC in cultures activated with SPB were hydroxyurea-resistant. These studies suggest that SPB is another useful polyclonal B-cell 'activator' for studies of human B-cell differentiation and function, and that SPB defines two distinct subsets of B cells.

A simple and rapid latex fixation test for measuring immunoglobulins produced in cell cultures

A rapid and simple latex fixation test (LFT), which quantifies immunoglobulin (Ig) released into culture supernatants is described. Latex particles are coated with rabbit anti-human IgG, IgA or IgM antibodies. With this LFT technique the concentration of Ig is determined within a few minutes. The LFT is as sensitive and quantitative as double-antibody radioimmunoassay and is capable of detecting 35, 68 and 225 ng/ml of IgG, IgA and IgM, respectively.

Polyclonal B-cell activation induced by extracts of Gram-negative bacteria isolated from periodontally diseased sites

The objective of this research was to determine whether gram-negative bacteria frequently isolated from periodontally diseased sites contained polyclonal B-cell activators. Polyclonal B-cell activation, which results in nonspecific activation of multiple B-cell clones was analyzed by a hemolysis-in-gel assay designed to detect a broad range of antibody specificities. Extracts from numerous bacterial strains, including Bacteroides gingivalis, Bacteroides melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. intermedius, Fusobacterium nucleatum, Selenomonas sputigena, Capnocytophaga ochracea, and Actinobacillus actinomycetemcomitans, were tested. Extracts of the above organisms were found to stimulate polyclonal antibody responses in cultures of normal human peripheral blood lymphocytes, although the magnitude of stimulation varied among the extracts. Optimal antibody-forming cell responses were found at stimulator doses between 5 and 1,000 micrograms/ml. We conclude that the resident gram-negative subgingival flora associated with periodontal lesions possesses potent polyclonal B-cell activators. These activators may contribute to disease pathogenesis by inducing B lymphocytes to produce antibody, osteolytic factors, or both and possibly other mediators of inflammation.

Immunological features of psoriasis. Effects of Ro-109359, concanavalin A, pokeweed mitogen, and methotrexate on cultivated lymphocytes

Isolated peripheral mononuclear cells of psoriasis patients with different disease characteristics, e. g. head-localised, quiescent guttata, confluent active widespread and erythrodermic, were cultured in a modified Mishell-Dutton system. Using the plaque-forming cell (PFC) assay, single cell antibody formation was studied, and class distribution monitored, adding pokeweed mitogen (PWM), concanavalin A (ConA), methotrexate (MTX) or Ro-109359/31, as well as autologous sera to the culture. PFC-estimation vs. sheep red blood cells (SRBC) and burro red blood cells (BRBC) revealed a distinct suppression of primarily IgG-PFC in some of the PWM-treated patients' cultures; ConA maximally reduced PFC by only 50%, compared to 100% for normal immune cells. Ro-109359/31 reduced mainly IgG-PFC in the co-cultures with PWM or autologous sera. MTX resulted in a reduction of IgG-PFC and IgM-PFC equally. The results were compared with cultured immune cells from normal individuals. The two antigenically different indicators, the partial abolition of ConA induced suppression, broad-based immunoglobulin elevation in the sera, and the mainly IgG-formation hint at the role of polyclonal B-cell activation in the perpetuation of psoriasis, which can be specifically reduced by Ro-109359/31. Suppressor cell dysfunctions remain to be discussed.

Stimulation of primary in vitro IgE antibody responses in culture of human peripheral mononuclear cells

Experiments are presented herein that demonstrate the capacity to stimulate human peripheral mononuclear cells to synthesize and secrete significant quantities of IgE molecules in vitro by exposure to appropriate concentrations of 2,4-dinitrophenyl (DNP)-protein conjugates, pokeweed mitogen (PWM), or a combination of DNP-proteins and PWM. Cultures stimulated in this fashion synthesize increased quantities of both total IgE and DNP-specific IgE antibody molecules. This in vitro human IgE antibody system should provide a useful tool for further exploration of regulatory control of IgE responses in both normal humans and those manifesting various forms of IgE-mediated allergic disorders.

Fc receptors on human T lymphocytes: loss of Fc mu and expression of Fc gamma receptors by T cells stimulated in mixed lymphocyte reaction

The consequences of allogeneic stimulation on the expression of Fc mu or Fc gamma receptors were analysed in T-cell populations responding in mixed lymphocyte reaction (MLR). Unfractionated T-cell populations were cultured with a pool or irradiated allogeneic T-depleted cells. The responder E-rosetting cells progressively lost Fc mu and acquired Fc gamma receptors. The change of the original Fc receptor phenotype is not the consequence of a preferential proliferative response of TG versus TM cells but is likely due to a de novo expression of Fc gamma receptors by T cells lacking detectable Fc receptors (T-null) and also to the loss of Fc mu and expression of Fc gamma receptors by TM cells. These data suggest that, after MLR, responder T cells can modify their Fc receptor phenotype.

Beneficial effects of oral zinc supplementation on the immune response of old people

Zinc is known to have beneficial effects on the immune response. In an attempt to modify age-associated immune dysfunction, supplemental zinc was administered to 15 subjects over 70 years of age (220 mg zinc sulfate twice daily for a month). As compared to 15 controls, matched for age and sex, there was a significant improvement in the following immune parameters in the treated group: (1) number of circulating T lymphocytes; (2) delayed cutaneous hypersensitivity reactions to purified protein derivative, Candidin and streptokinase-streptodornase; (3) immunoglobulin G (IgG) antibody response to tetanus vaccine. Zinc treatment had no influence on the number of total circulating leukocytes or lymphocytes, or on the in vitro lymphocyte response to three mitogens: phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). The data suggest that the addition of zinc to the diet of old persons could be an effective and simple way to improve their immune function.

The maintenance of B-cell and T-cell function in frozen and stored human lymphocytes

The objective of this study was to identify and test a convenient means for long-term storage of lymphocytes taken from clinically characterized patients without losing B- or T-cell function. Accordingly, peripheral blood lymphocytes were frozen and stored, and portions of each sample were subsequently assayed for T-cell blastogenic response and B-cell Jerne plaquing at various time intervals after freezing. A comparison of the cell counts of fresh and frozen cultures indicated that cell were recovered after freezing. Furthermore, these cells showed no significant differences in (i) cell viability; (ii) blastogenic response to antigens of Actinomyces maeslandii, Bacteroides melaninogenicus, Fusobacterium nucleatum, and tetanus toxoid; (iii) blastogenic response to phytohemagglutinin and pokeweed mitogen; and (iv) polyclonal B-cell response to pokeweed mitogen as measured by the direct Jerne plaque assay. The retained blastogenic and plaquing responses seen in frozen cultures indicated the maintenance of both T-cell and B-cell function, respectively. This is the first reported demonstration of Jerne plaquing of normal human lymphocytes after freezing. It appears that freezing techniques provide a means for repeating and extending both T- and B-cell assays using frozen stored portions of the same cell samples.

Antigen-induced in vitro antibody production in humans: a model for B cell activation and immunoregulation

The precise events associated with B cell activation in humans are a subject of intense investigation. It has been difficult to develop an in vitro model of antigen-specific triggering of antibody synthesis by human peripheral blood mononuclear cells that is independent of exogenous mitogens. In the present study a sensitive and reproducible culture system and enzyme-linked immunosorbent assay have been established wherein antigen alone is used to trigger antigen-specific antibody synthesis by mononuclear cells from subjects immunized to keyhole limpet hemocyanin (KLH). The in vitro antigen-induced anti-KLH response is comparable in magnitude to that induced by pokeweed mitogen, is predominantly IgM in isotype, and is accompanied by a simultaneous increase in polyclonal antibody production. Anti-KLH responses were seen at in vitro KLH concentrations as low as 0.05 microgram/ml. However, concentrations of KLH greater than 5 microgram/ml resulted in profound suppression of the anti-LHL response while continuing to trigger large amounts of total polyclonal immunoglobulin synthesis. This suppression by high concentrations of antigen was also observed in pokeweed mitogen-driven anti-KLH production. These observations are consistent with previous results from the mouse model showing a close association between antigen-specific and polyclonal responses and the phenomenon of antigen-induced, antigen-specific suppression. Thus, an in vitro model of antigen induction of antigen-specific antibody synthesis in human peripheral blood mononuclear cells has been demontrated and should prove useful in exploring the mechanism of human B cell activation and immunoregulation.

Human B lymphocyte subsets. I. IgG-bearing B cell response to pokeweed mitogen

The subset of B lymphocytes having IgG on their surfaces was purified from human spleen and blood using a fluorescence-activated cell sorter (FACS). This subset constituted about 15% of B lymphocytes. The remaining non-IgG-bearing B cells were also obtained for study. These two populations were examined for (a) their expression of other surface immunoglobulin isotypes, (b) their ability to give rise to IgG- and IgM-secreting (plaque-forming) cells in a pokeweed mitogen (PWM)-driven culture system, and (c) their ability to proliferate in response to PWM stimulation. The results of these studies indicate that most IgG-bearing B cells also express surface IgM and IgD. Less than 15% had only IgG. The IgG-positive cell gave rise to both IgG and IgM plaque-forming cells when driven by PWM, and in fact were responsible for most of the total plaque response in both the IgG and IgM classes. The non-IgG-bearing B cells were depleted of both IgG and IgM responsiveness. The failure of the non-IgG-bearing B cells to give a strong response to PWM did not appear to be due to either depletion of accessory cells or to any suppressive influence. Finally, proliferation studies indicated that both the IgG-bearing and the non-IgG-bearing cells proliferated in the presence of PWM with a somewhat stronger proliferative response in the IgG-bearing cells. These results demonstrate that the IgG-bearing cell is not irreversibly committed to IgG production but can also give rise to IgM-secreting cells, and that human PWM-driven immunoglobulin secretory responses are predominantly due to a numerically small subset of B cells.

Immunoregulatory T-cell dysfunction in polyclonal gammopathy

The mechanisms responsible for the increased serum immunoglobulines in polyclonal gammopathy states are unknown. We have studied the regulation of peripheral blood B-cell immunoglobulin synthesis and secretion, by T cells of either blood or bone marrow compartments, in 20 patients with polyclonal gammopathy and 27 controls with normal serum immunoglobulin levels. When compared to B-T-cell cocultures of normals, cocultures of polyclonal gammopathy patients had significantly higher levels of immunoglobulin secretion (P less than 0.01). Normal T cells but not T cells from patients with polyclonal gammopathy suppressed B-cell immunoglobulin secretion (P less than 0.01) and not the number of cytoplasmic immunoglobulin-positive cells of the polyclonal gammopathy patients. T cells from patients with polyclonal gammopathy enhanced normal B-cell immunoglobulin secretion (P less than 0.05) but not the number of cytoplasmic immunoglobulin-positive cells. Controls' bone marrow T cells were more efficient than blood T cells in suppressing polyclonal gammopathy B cells (P less than 0.02). T cells in polyclonal gammopathy are predominantly helper cells and could play a role in the enhanced immunoglobulin secretion of B cells. Bone marrow T cells are more efficient than blood T cells in regulating B cells. It seems that T cells predominantly regulate B-cell immunoglobulin secretion and not the number of B cells with cytoplasmic Ig.

B lymphocyte colony formation in vitro: ultrastructural development of individual colonies

B lymphocyte colony development in agar culture was studied using an electron microscope, and more than 3,000 colony cells were identified and photographed. In early cultures (day 4) lymphoblasts dominated the colonies. From day 5 onwards plasmablasts and small lymphocytes were present in colonies. From day 6 onward mature plasma cells were observed in increasing numbers. On day 9 culture the colonies started to degenerate and on day 10 of culture approximately 70% of the colony consisted of pyknotic and degenerating cells. Topographically, the degenerating cells were concentrated in the center of the colony whereas proliferation took place in the periphery. Colony growth occurred in an exponential fashion, the number of viable colony cells being maximal on day 8 of culture (400-600 cells/colony). At this time the frequencies of the four B cell categories were: lymphoblasts 72%, plasmablasts 20%, plasma cells 6%, and small lymphocytes 2%. Recloning experiments showed that dispersed colony cells were capable of forming only small cell clusters. It is concluded that B lymphocyte colony formation reflects a series of B cell developmental stages including the formation of the end cell categories o this lymphocyte lineage.

Heterogeneity of b lymphocyte differentiation in severe combined immunodeficiency disease

Pokeweed mitogen-induced B lymphocyte differentiation in vitro into antibody secreting plaque-forming cells (PFC) was investigated in nine patients with severe combined immunodeficiency having variable proportions of circulating B lymphocytes. When cultured by themselves, the peripheral blood mononuclear cells did not respond to stimulation with pokeweed mitogen in any patient. In the presence of irradiated allogeneic T cells as helpers, however, PFC responses were elicited in lymphocyte cultures from peripheral blood and/or bone marrow in some patients. In one of these patients, results of allogeneic co-culture experiments were suggestive of genetically restricted suppressor cells. In a single patient with deficiency of the enzyme adenosine deaminase, PFC were generated in bone marrow lymphocyte cultures only when they were supplemented with exogenous adenosine deaminase and allogeneic helper cells. A parallel study of T lymphocyte differentiation in vitro performed in fractionated bone marrow cells was suggestive of arrested differentiation at different steps along the differentiation pathway. In two patients with evidence of functional B cell precursors, deficiencies of helper T cell function could be attributed to differentiation defects at the level of the stem cells in one and the thymus in the other. The findings reported here further substantiate the heterogeneity of the severe combined immunodeficiency disease syndromes.

A new solid-phase radioimmunoassay to measure IgG secreted by cultured human lymphocytes

We describe a simple solid-phase radioimmunoassay (RIA) to detect IgG based on competitive binding between radiolabeled and unlabeled IgG for anti-IgG antibody physically adsorbed to the wells of polyvinyl microtiter plates. The assay is sensitive (1 ng), rapid, and is particularly suited for studies of in vitro IgG secretion by human peripheral blood lymphocytes, since such studies require large numbers of cultures. Conditions which permit measurement, by means of this assay, of helper and suppressor T cell effects on IgG production by human B cells in culture are described.

In vitro idiotypic suppression of chronic lymphocytic leukemia lymphocytes secreting monoclonal immunoglobulin M anti-sheep erythrocyte antibody

A patient with chronic lymphocytic leukemia was found to have B cells with surface immunoglobulin (Ig)M manifesting anti-sheep erythrocyte (SRBC) specificity together with a high titer serum monoclonal anti-SRBC IgM antibody. By immunizing a sheep with the monoclonal IgM antibody, followed by multiple absorptions against normal human IgM, an anti-idiotype (Id) antibody was obtained. The serum IgM anti-SRBC antibody was then demonstrated to share the same idiotypic determinants with the surface IgM with anti-SRBC specificity on the patient's B cells. The anti-Id antibody suppressed the spontaneous secretion of anti-SRBC antibody as well as the pokeweed mitogen-induced anti-SRBC antibody production as measured by a hemolysis-in-gel plaque-forming cell assay. In contrast, pokeweed mitogen-induced anti-SRBC plaque-forming cell responses of normal individuals were not suppressed by the anti-Id antibody. Thus, this study demonstrates in vitro suppression of human B-cell function by anti-Id antibody.

Immunoregulation in Sjögren's syndrome: influence of serum factors on T-cell subpopulations

21 patients with Sjögren's syndrome (sicca syndrome) with either glandular or extraglandular involvement, but without other connective tissue diseases, were studied with regard to immunoregulatory T-cell subpopulations, B-cell function, and suppressor cell capabilities. Patients with isolated glandular disease as well as patients with extraglandular disease had normal absolute numbers of total lymphocytes, T cells, and B cells. However, 9 of 11 patients with extraglandular disease and only 3 of 10 patients with glandular disease had decreased relative proportions of T cells bearing receptors for the Fc portion of immunoglobulin (Ig)G (T(G)) which was explained by a factor that blocked the expression of the IgG Fc receptor on T(G) cells. This blockage was reversible since the factor could be removed by trypsinizing the T cells before T(G) determination. Serum from patients with abnormal proportions of T(G) cells, but not serum from patients with normal proportions of T(G) cells, blocked the expression of the IgG Fc receptor on normal T cells. The serum factor upon fractionation over Bio-Gel A 1.5 columns as well as over staphylococcal protein A-Sepharose 4B columns was found diffusely within the IgG fraction, and not in the IgM fraction. Neither patients with glandular nor patients with extraglandular disease manifested increased numbers of in vivo-activated circulating lymphocytes as determined by spontaneous anti-trinitrophenyl (TNP) plaque-forming cells (PFC). However, patients with glandular disease had reduced numbers of pokeweed mitogen-induced anti-sheep erythrocyte PFC (P < 0.01) as compared with normals and patients with glandular disease. Of note was the fact that despite the modulation of T(G) subpopulation by the serum factor in patients with extra-glandular disease, these patients manifested normal concanavalin A-generated suppressor cells of pokeweed mitogen-induced PFC responses in allogeneic co-cultures. This was unlike the suppressor cell defect previously described in this system with systemic lupus erythematosus patients. The discrepancy was attributed both to the fact that the T(G) defect was reversible and to the fact that concanavalin A-generated suppressor cells are not limited to the T(G) subset. Thus, these studies have demonstrated reversible abnormalities in T(G) cells in patients with extraglandular Sjögren's syndrome which are not associated with suppressor cell defects. The discrepancy between these findings and the immuno-regulatory defects demonstrated in systemic lupus erythematosus may explain the difference in severity of the autoimmune expression in these diseases.

Activation of human B lymphocytes (the in vitro polyclonal B cell activator-induced plaque-forming cell system)

The characteristics of human B lymphocyte triggering, differentiation, and regulation are described using the polyclonally induced anti-sheep red blood cell hemolytic plaque-forming cell assay system. Technical and methodologic considerations, cellular requirements and mechanisms of regulation including suppressor and helper influences are discussed. Also considered are theoretical concepts regarding normal immune response versus pathologic immune states and the potential biologic role of polyclonal activation in these human immune mechanisms.