FcR+ and FcR- monocytes differentially secrete monokines during pokeweed mitogen-induced T-cell-monocyte interactions

Monocyte subpopulations which differ in the expression of Fc receptor for human IgG (FcRI) differentially regulate the T-cell-dependent, pokeweed mitogen (PWM)-induced, polyclonal B-cell response. We, thus, studied the cytokine production in human peripheral blood monocyte and T-lymphocyte cultures activated with this lectin. Monocytes or their FcR+ and FcR- subpopulations stimulated with PWM were cultured with or without T lymphocytes or their CD4+ and CD8+ subsets. Both monocyte subpopulations cultured alone produced similar amounts of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), but FcR- monocytes showed significantly enhanced ability to secrete interleukin-1 (IL-1). T cells, especially CD4+, added to monocyte cultures enhanced IL-1 production. This enhancement was presumably due to interferon-gamma (IFN-gamma) release by T lymphocytes, since this lymphokine enhanced IL-1 secretion when added to PWM-stimulated cultures of monocytes. Addition of monocytes, in particular the FcR+ subpopulation, greatly enhanced production of IFN-gamma by T lymphocytes. Although both T-cell subsets produced IFN-gamma, the CD4+ cells were more efficient. These results indicate that in PWM-stimulated cultures subpopulations of monocytes differ in secretion of cytokines, which might explain their differential effect on T-cell-dependent immune responses in vitro.

Abnormal in vitro immunoglobulin synthesis in surgical patients

Blood mononuclear cells from surgical patients produce large amounts of IgG in vitro. This synthesis is not increased by stimulation with pokeweed mitogen. To determine if this abnormal pattern of IgG synthesis extended to other immunoglobulin classes, surgical patients were stratified according to delayed-type hypersensitivity responses as reactive or anergic. Healthy personnel were studied as controls. Mononuclear cells were cultured without or with pokeweed mitogen, and IgG, IgM, and IgA were measured in supernatants. Unstimulated IgG and IgA synthesis was increased in surgical patients, especially in those with reduced delayed-type hypersensitivity responses. Synthesis of IgM was normal or low. With mitogen stimulation, IgG synthesis was increased in control and reactive subjects, but not in anergic subjects. For IgM, mitogen stimulation increased synthesis to a less than normal level in all patients. For IgA, synthesis was increased in all groups.

Interleukin 4 inhibits polyclonal immunoglobulin secretion and cytokine production by peripheral blood mononuclear cells from rheumatoid arthritis patients

Rheumatoid arthritis (RA) is associated with T- and B-cell dysfunction. Immunoglobulin (Ig) production is under the control of T cells and their derived cytokines such as interleukin 2 (IL-2) and IL-4. Herein we studied the regulation of the production of immunoglobulins and cytokines by peripheral blood mononuclear cells from RA patients and controls. In the controls, IL-4 inhibited Ig production in response to Staphylococcus aureus and pokeweed mitogen stimulation. IL-2 induced maximal Ig production in association with Staphylococcus aureus, whereas it inhibited pokeweed mitogen-induced production. In patients, levels of Ig production in response to mitogens and cytokines were reduced, particularly for the response to IL 2. The inhibitory effect of IL-4 on mitogen-induced Ig production was observed in RA patients as in the controls. Spontaneous production of IL-6 was increased in RA patients. These levels were correlated with indicators of active disease such as sedimentation rate and Ritchie index. IL-4 inhibited the production of IL-6, IL-1 beta, and tumor necrosis factor alpha (TNF alpha) by both controls and rheumatoid patients. Thus as first described for the T-cell response, mononuclear cells from RA patients display a reduced response to mitogens and cytokines which induce their B-cell differentiation into Ig-screening cells. However, IL-4 was able to inhibit Ig and cytokine production, properties suggesting a potential antiinflammatory role for this cytokine.

In vitro immunization of human lymphocytes with human lung cancer cell line A549

We established a method of in vitro immunization of human lymphocytes against human cancer cells and efficiently obtained human-human hybridomas producing cancer-specific antibodies using the in vitro immunized lymphocytes. Human lymphocytes were cocultured with human lung cancer cell line A549 for four days in medium containing various immunoactive reagents. In vitro immunization was effectively caused by the addition of OK-432 or muramyl peptides, IL-2, and IL-6, to the coculture of A549 cells and lymphocytes. Although specific antibodies of both IgM and IgG classes were produced by this method, the ratio of IgG to IgM was greater than or equal to 2. The efficiencies of in vitro immunization fluctuated about threefold in lymphocytes derived from several donors. The in vitro immunized lymphocytes were fused with human fusion partner A4H12 cells. Hybridomas producing specific antibodies reactive to A549 cells were efficiently obtained by sequential cell fusion. The efficiency of acquisition of hybridomas producing specific antibodies with the in vitro immunized lymphocytes was about 10-fold higher than that with lymphocytes spontaneously immunized in bodies of lung cancer patients.

Comparison of IgE expression at the mRNA and protein levels in vitro

The regulating effects of IL-4 and pokeweed mitogen on IgE synthesis in vitro by human peripheral blood leucocytes has been compared with the corresponding effect of these regulators on the expression of IgE mRNA. The latter was measured by dot blot hybridization with an oligonucleotide coding for a unique six amino acid region of the CH epsilon 2 domain. Specificity of the oligonucleotide probe was established by its inability to hybridize with RNA extracted from HMY-2 (IgG) and XQ-15 (IgM) secreting cell lines whilst producing intense signals with RNA extracted from the IgE secreting cell line U266. Whilst IgE mRNA was detected in RNA extracted from PBL of both atopic and control subjects, spontaneous IgE synthesis was restricted to atopic PBL. IL-4 increased both IgE mRNA and IgE synthesis in all PBL samples but PWM, while significantly increasing IgE mRNA expression either failed to modify IgE synthesis or actively suppressed it. The assay system employed to quantitate IgE synthesis in vitro was shown to be inhibited by both IgE binding factors and IgG anti-IgE autoantibodies which are produced in PBL cultures. IgE mRNA levels might therefore more accurately monitor the regulatory effects of IL-4 and PWM on IgE synthesis than quantitation of the IgE by radioimmunoassay.

Effect of ozone on immunoglobulin production by human B cells in vitro

Animal studies indicate that ozone (O3) inhalation results in reduced ability to generate a humoral response to soluble and particulate antigens. In this study, human lymphocytes have been exposed to O3 in vitro (1.0, 0.5, and 0.1 ppm/2 h) and then evaluated for the ability of B cells to produce immunoglobulin G (IgG) in response to the T-cell-dependent stimulus pokeweed mitogen (PWM), and to the T-cell-independent stimulus Staphylococcus aureus Cowan I strain (SAC). Suppression of IgG production was found with O3-exposed PWM-stimulated lymphocytes, while no effect of O3 was seen with SAC-stimulated cells, suggesting that T cells, but not B cells, were sensitive to O3. However, exposing either cell type alone to O3 indicated that both T cells and B cells were affected by the pollutant. The O3-exposed B cells produced less IgG in response to PWM but produced more IgG in response to SAC. On the other hand, O3-exposed T cells were suppressive in both PWM and SAC responses. Since the differentiation of B cells into plasma cells is regulated by complex interactions of cytokines secreted by T cells and antigen-presenting cells, possible O3-induced alterations in secretion of some of these regulatory lymphokines (IL-2, IL-4, IL-6, and IFN-gamma) were investigated in lymphocyte cultures stimulated with PWM. A decrease in IL-2 production was found, while in contrast, IL-6 production was significantly increased. IFN-gamma secretion was not altered, and IL-4 levels were below the limits of detectability. These results suggest that O3-induced changes in IgG production may be mediated by altered production by T cells of important immunoregulatory molecules, in addition to any direct effects of O3 on the IgG-producing cells themselves.

Size, CD4 and CD8 marker profiles and functions of lymphocyte subpopulations in mucosal-associated lymph nodes

We analyzed phenotypic and functional characteristics of T cell populations in mucosal-associated supramammary and mesenteric lymph nodes in goats. Here we demonstrate, by flow cytometry, quantitative differences in CD4 and CD8 T cell subsets among large and small mucosal-associated lymphocyte populations and their differential regulatory activities on resident lymph node B cells stimulated with Staphylococcus aureus Cowan I or pokeweed mitogen. The CD4/CD8 T cell ratio was lower in mesenteric lymph nodes (1.46) when compared to that of supramammary lymph nodes (2.18). Analysis of large and small lymphocyte subpopulations from lymph nodes showed nearly 62% of the lymphocytes from mesenteric lymph nodes being of large cell phenotype with CD4/CD8 ratios of 1.34. In contrast, large cell subpopulations in supramammary lymph nodes showed a significantly lower number (50%) with a higher CD4/CD8 ratio of 2.05. Functionally, mesenteric lymph node T cells, isolated by nylon wool, showed heightened suppressive activity in mitogen-driven B cell proliferation responses, whereas T cells from supramammary lymph nodes were stimulatory. These findings clearly demonstrate distinctive functional properties between resident T cell populations of supramammary and mesenteric lymph nodes, suggesting that different proportions of T cell subsets in these nodes are activated and thus regulate regional immune responses via different pathways.

Effect of selenium and reducing agents on in vitro immunoglobulin M synthesis by bovine lymphocytes

A series of experiments was conducted to evaluate the effects of inorganic and organic forms of Se with or without reducing agents on in vitro IgM production by bovine lymphocytes. Peripheral mononuclear cells were isolated from nonlactating Jersey cows fed a diet with adequate Se. Cells were stimulated with pokeweed mitogen and, in addition, were cultured with various Se compounds at a concentration of 100 ng Se/ml. Mercaptoethanol (50 microM) and glutathione (1 mM) were included in cultures of cells stimulated by pokeweed mitogen with and without inorganic Se. Sodium selenite was less effective than selenomethionine and selenocystine in augmenting pokeweed mitogen-induced Ig synthesis. The addition of mercaptoethanol to pokeweed mitogen-stimulated control cultures enhanced in vitro IgM production, whereas the addition of glutathione had a negligible effect, but addition of either in combination with sodium selenite dramatically depressed IgM production. These results suggest that Se in inorganic or organic forms enhances B-cell function in vitro.

Synergistic effect on blastogenesis in murine spleen cells of lipopolysaccharide, lipid A, and acid-degraded polysaccharide from Fusobacterium nucleatum

Interchangeable combinations of Fusobacterium nucleatum Fev1 lipopolysaccharide (LPS) with its split products by acetic acid hydrolysis, i.e. lipid A (LA) and degraded polysaccharide (PS), amplified the blastogenic response in murine spleen cell cultures as measured by [3H]thymidine uptake. Athymic murine spleen cells precultured with LPS-Fev1 for 48 h (stage 1), washed twice and cultured together with fresh cells and either LA or PS for 72 h (stage 2) gave a synergistic response over that found in spleen cell cultures of thymic mice. Spleen cells pre-cultured with LA or PS and with fresh cells and LPS-Fev1 added to stage 2 cultures gave less significant amplification compared with precultures of LPS and either LA or PS together with fresh cells added to stage 2. Precultures with LA, PS or LPS-Fev1 and with pokeweed mitogen (PWM) and fresh cells added produced an additional increment of synergy which was most pronounced in spleen cell cultures of normal mice.

Differential effects of retinoids on pokeweed mitogen induced B-cell proliferation vs immunoglobulin synthesis

The effects of three retinoids, all-trans-retinoic acid (RA), 13-cis-retinoic acid (cRA), and N-(4-hydroxyphenyl) retinamide (4-HPR) on mouse splenocyte responses to pokeweed mitogen (PWM) and Escherichia coli lipopolysaccharide (LPS) in vitro were evaluated. All three retinoids caused a dose dependent increase in the proliferative response to PWM. The retinoids hierarchy of efficacy based on potentiation of PWM-induced splenocyte proliferation was RA greater than cRA greater than 4-HPR. 13-cis-retinoic acid and 4-HPR also resulted in significant increases in Ig secretion in response to PWM. However, RA did not produce a significant increase in secretion compared with cells treated with PWM alone. The efficacy hierarchy of retinoids ability to potentiate Ig secretion was 4-HPR greater than cRA greater than RA. All three compounds did not affect Ig secretion from LPS-stimulated splenocytes and produced dose dependent decreases in proliferation. Both inhibition of LPS-induced proliferation and potentiation of PWM-induced proliferation were maximal when the retinoids were added during the first hour of culture. These results indicate that retinoids have a differential effect on Ig secretion and B-cell proliferation based on structural differences of the retinoids. Potentiation of proliferation and Ig secretion are both T-cell dependent and could be a result of increased lymphokine synthesis by the T-cells or increased responsiveness to the effects of the T-cell produced lymphokines.

Polyclonal stimulation of human B lymphocytes derived from fetal liver and spleen cells at different stages of ontogeny

The functional capacity of human lymphocytes derived from fetal liver and spleen at different stages of ontogeny (16-34 weeks of gestation) was studied using in vitro models (increase in cell volume, [3H]thymidine incorporation, Ig secretion) reflecting various stages of activation induced by mitogens (LPS, PWM) in vitro. Lymphocytes differed in their reactivity to LPS depending on the period of intrauterine development: cells from the early liver could respond with enhanced IgM production whereas lymphocytes derived from this organ after more than 25 weeks failed. The opposite was found to apply to spleen cells: only lymphocytes derived from the organ after more than 25 weeks showed significant LPS-induced in vitro differentiation. These data were in correlation with the proliferative response to LPS. It was clear that the number of CD20-positive mature B cells in the lymphocyte preparations was not responsible for these results, since comparable yields were found throughout the period of fetal development of the liver studied, whereas in the spleen increasing numbers of B cells were seen.

Monocyte-T-cell interactions in pokeweed mitogen-activated cultures

Monocyte-T-cell interactions were studied in pokeweed mitogen (PWM)-activated cell cultures. We addressed the question of monocyte changes in PWM-stimulated cultures of T cells and monocytes and found, by flow cytometric analysis, that PWM activation led to a loss of cells with monocyte or macrophage phenotype (CD14, HLA-DR, HLA-DQ) within 48 hr of culture in the presence of T cells (CD4+ T cells), but not in cultures of pure monocytes. Chemiluminescence measurements revealed that phagocytic stimulation of monocytic superoxide release was impaired in PWM-stimulated cultures of monocytes plus T cells, but not in PWM-stimulated cultures of pure monocytes. Furthermore, PWM induced the secretion of interferon-gamma (IFN-gamma) in primary cultures of T cells supplemented with 20% of monocytes, whereas in subsequent secondary cultures of these cells PWM induced IFN-gamma only when monocytes were added. We conclude from these flow cytometric and functional analyses that monocytes are efficiently eliminated from PWM-activated T-cell/monocyte cultures by CD4+ T lymphocytes.

Basic studies on a new material for inducing antitumor immune cells

Recently, adoptive immunotherapy for cancer with lymphokine activated killer (LAK) cells has been widely used experimentally. The therapy has several problems, including difficulty in handling, sterilization, and time consumption. To solve these problems, new materials able to induce antitumor immune cells were investigated. Pokeweed mitogen (PWM) and PWM-conjugated materials (CMC-1) could induce strong killer cells by short-term stimulation of human peripheral blood lymphocytes (PBL). The induced killer cells showed a wide killing spectrum in vitro against human tumor cell lines (MKK-1, PRMI4788, NBT-2, ZR-7530, H-1, Hela, KB, HMV-1, PC-10, C-1). Human PBL stimulated for a short time by CMC-1 also showed a tumoricidal effect on tumor bearing (MKN-1, MKN-45) nude mice. These results suggest that CMC-1 may solve the problems with currently used LAK therapy and may provide easily applicable extracorporeal immunotherapy for cancer.

Decrease in mitogen-induced lymphocyte proliferative responses in cats infected with feline immunodeficiency virus

The blastformation tests using concanavalin A and pokeweed mitogen were carried out on peripheral blood lymphocytes obtained from cats infected with feline immunodeficiency virus (FIV). The infected cats included those showing multiple chronic disease, those with a single mild sign, and one with no clinical sign. The infected cats showed significantly lower mitogenic responses of peripheral lymphocytes to both mitogens and lower lymphocyte counts as compared to uninfected healthy cats. These immunologic alterations in the infected cats may be closely related to the development of immunodeficiency-like disorders associated with FIV.

Changes in lymphocyte blastogenic response of mares during the perinatal period

A fluorometric assay was applied to evaluate blastogenesis of equine lymphocytes. Optimal culture conditions were as follows; concentrations of phytohaemagglutinin-P (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were 1 microgram/ml, 40 micrograms/ml and 10 micrograms/ml, respectively, when 5 X 10(5) lymphocytes were incubated with culture medium containing 20% pooled horse serum (PHS) for 120 hours. The relative mean stimulation index of healthy non-pregnant mares were 5.107 +/- 0.323 (M +/- SE) with PHA, 4.019 +/- 0.183 with Con A and 3.610 +/- 0.131 with PWM. Sequentially the blastogenic responses of lymphocytes from twenty mares were observed during various stages of the perinatal period. Response decreased gradually before parturition was lowest at the time of parturition (PHA: 1.923 +/- 0.174, Con A: 1.698 +/- 0.206 and PWM: 1.706 +/- 0.177), and then increased gradually after parturition towards non-pregnant levels.

Helper T cell-dependent human B cell differentiation mediated by a mycoplasmal superantigen bridge

Experimentally induced murine graft-vs.-host disease may be characterized by hypergammaglobulinemia, autoantibody formation, and immune complex-mediated organ system damage that mimics SLE. These autoimmune phenomena are mediated by abnormal Th-B cell cooperation, across MHC disparities, in which donor-derived allospecific Th cells recognize and interact with MHC class II antigens on the surface of recipient B cells. Microbial toxins, termed superantigens, which bind to MHC class II molecules and activate selected T cells based on TCR variable gene usage, may induce a similar form of Th-B cell interaction. In the present study, we generated and characterized human Th cell lines reactive with the Mycoplasma arthritidis superantigen (MAM). The essential observation is that resting human B cells bind MAM and present it to superantigen-reactive autologous or allogeneic Th cells, resulting in both Th cell activation and a consequent polyclonal Ig response by the superantigen-bearing B cells.

[Effects of IL-2 and IL-6 on the immunoglobulin synthesis of lymphocytes from CVID patients]

Peripheral blood lymphocytes from five hypogammaglobulinemic patients suffering from common variable immunodeficiency (CVID) were stimulated with Staphylococcus aureus Cowan I (SAC) and pokeweed mitogen (PWM). The assays were substituted with interleukin-2 (IL-2) and interleukin-6 (IL-6) in different combinations. In three patients who were deficient for IgM in vivo a combination of SAC and IL-2 induced a normal IgM synthesis in vitro. In these patients a deficient IL-2 synthesis is probably the cause of CVID. In only one patient a "class switch" from IgM to IgG was detectable. Stimulation with PWM which is T-cell-dependent induced in one out of the five patients a normal IgM synthesis. Another CVID patient showed no defect in IgM or IgG synthesis in vitro. With these in vitro assays it seems possible to identify CVID patients who might profit from a therapy with human IL-2 in vivo.

Sarcocystis gigantea lectin--mitogen and polyclonal B-cell activator

The present study further examined the in vitro response of human mononuclear cells (MNC) to the Sarcocystis gigantea lectin (SGL). The results confirm our previous report that SGL is mitogenic for human MNC. We now report that SGL is not only a potent mitogen but also a polyclonal activator for human peripheral B cells. As was true for pokeweed mitogen (PWM, 2 micrograms/ml), the addition of SGL (25 micrograms protein/ml) to cultures of MNC caused lymphocyte proliferation and B-cell maturation, indicated by a marked increase in IgG and IgM production. As measured by the [3H]-thymidine incorporation assay, SGL induced significantly higher proliferative responses than PWM (P less than 0.01, n = 24). The values obtained by SGL and PWM for IgG and IgM synthesis were essentially identical. As opposed to SGL, the sarcotoxin-containing fraction (SGTF) did not induce antibody formation or proliferative responses in human MNC.

Normal mitogen-induced suppression of the interleukin-6 (IL-6) response and its deficiency in systemic lupus erythematosus

A low-frequency suppressor-cell population in normal peripheral blood inhibits the B-cell CESS response to IL-6, following pokeweed mitogen stimulation. The suppression of IL-6 responsiveness is (i) radiation sensitive, (ii) directed against CESS targets and not mediated by inhibition of IL-6 production, and (iii) associated with nonspecific cytotoxic activity against CESS targets. The generation of these cytolytic cells is also radiation sensitive. A correlation was found between PWM-induced cytotoxicity against CESS and the suppression of IL-6-dependent IgG production. But cytotoxicity toward CESS targets is not responsible for this suppression because (i) IL-2 induces equivalent or greater nonspecific cytotoxicity against CESS in the total absence of suppression of CESS-derived IgG production and (ii) suppression is also induced by mitogen-activated PBL separated from CESS targets by a cell-impermeable membrane. This suppression was not mediated by TNF alpha/beta or IFN-gamma. In systemic lupus erythematosus, suppression of IL-6-dependent IgG production is impaired in patients with active disease (29.2 +/- 13.7%) compared to patients with inactive disease (70 +/- 19.5%) or normal controls (82.8 +/- 9.2%). There is also a defect in mitogen-induced nonspecific cytotoxicity in active SLE (specific lysis 15.1 +/- 3.5%, compared to 34 +/- 4% in normals). Pokeweed mitogen-activated PBL can therefore normally induce suppression of B-cell IL-6 responses and this response is deficient in lupus.

Comparative effect on humoral response of four different proteins covalently linked on BSA-containing liposomes

The humoral response to encapsulated BSA appears to be a classical TD antigen response with a high ratio of IgG to IgM, whereas that to covalently-linked antigen is more complex, characterized by an enhanced synthesis of IgM, leading to an equal production of IgM and IgG. In a recent paper, we observed that surface-linked Con A on BSA-containing liposomes changed the isotype distribution to encapsulated BSA so as to mimic the response to surface-linked antigen. In the present study, we compared the immune response to BSA in BALB/c mice immunized with the antigen encapsulated into liposomes coated with one of four different proteins: Con A, Myo, MSA, or PWM. The humoral response was analyzed by measurements of antibody production (total Ig, IgM, and IgG isotypes) on serum samples obtained by cardiac puncture. It can be concluded from our results that any surface-linked protein may affect the interaction between liposome-associated antigen and immunocompetent cells.

In vitro modulating effects of porcine immunoglobulin G on mitogens-induced lymphocyte response in precolostral, suckling and weaned piglets

The influence of allogeneic IgG on in vitro reactivity of peripheral blood lymphocytes (PBL) of neonatal colostrum-deprived piglets as well as of suckling and weaned piglets was studied. PBL were preincubated with purified allogeneic IgG for 24 h before their ability to respond to PHA, Con A or PWM was tested. PBL of precolostral piglets pretreated with allogeneic IgG exhibited higher response to PHA (P less than 0.01) than untreated control cells. An increased response of PBL treated with IgG was also observed in suckling piglets as compared to their respective control cells (P less than 0.01). Responsiveness of PBL treated with IgG to PWM was suppressed. No differences in response to Con A regardless of the sources of lymphocytes was observed as compared to IgG untreated controls. The results suggest that pretreatment of lymphocytes of piglets with allogeneic IgG modulates their reactivity to mitogens, suppressing the response to PWM and stimulating the response to PHA, respectively.

Specific immune response of the adenoids to a respiratory antigen

The specific antibody response of the adenoids to a respiratory antigen was investigated, both in vitro and in vivo. The in vitro immunoglobulin (Ig) production of adenoidal and tonsillar lymphocytes in the same patient in 18 cases was measured by an enzyme-linked immunosorbent assay. Adenoidal lymphocytes produced more IgM than IgG or IgA under culture conditions without any mitogens, whereas IgG was the major Ig produced by tonsillar lymphocytes. The same results were obtained when cultured with pokeweed mitogen. Under culture conditions with Dermatophagoides farinae (mite) antigen, adenoidal lymphocytes produced only specific IgM class antibody, and at a level significantly greater than tonsillar lymphocytes. Through an in vivo study, we established experimental adenoidal tissue in the guinea pig by long-term exposure to an ovalbumin aerosol. Infiltration of cells producing the specific antibody against an ovalbumin was demonstrated in the epipharyngeal mucosa using immunofluorescent staining. Our results confirm that the adenoids play a role in specific immune responses to respiratory antigens.

Mitogen-induced human IgG subclass expression. II. IgG1 and IgG3 subclasses are preferentially stimulated by a combination of Staphylococcus aureus Cowan I and pokeweed mitogen

Mitogens generally stimulate human IgG subclass production in amounts proportional to their abundance in serum (IgG1 greater than IgG2 greater than IgG3 greater than IgG4). We report here that a combination of Staphylococcus aureus Cowan strain I and pokeweed mitogen consistently stimulates human peripheral blood lymphocytes in vitro to preferentially produce more IgG1 and IgG3 than IgG2. This preferential stimulation can be measured by increases in the number of immunoblasts (cells with detectable cytoplasmic immunoglobulin) as well as in secreted immunoglobulin. The preferential stimulation pattern is established by the fourth day of culture and is maintained at least until the tenth day. Removal of T cells and subsequent stimulation of B cells with S. aureus Cowan I and interleukin 1 (IL-1) interleukin 2 (IL-2), interleukin 4 (IL-4), or interferon-gamma (IFN-gamma) failed to enhance any IgG subclass production, indicating the requirement for multiple lymphokines in IgG subclass production. The significance of these findings is discussed with respect to B-cell regulatory molecules and the coordinate expression of IgG subclasses.

Use of an autologous reaction in vitro to assess contributions of T and B lymphocytes to immune hyperreactivity of atopics

The in-vitro proliferation reaction of peripheral blood lymphocytes (measured by [3H]thymidine incorporation) to autologous pokeweed mitogen (PWM)-induced lymphoblasts (PWM-lymphoblast-stimulated autologous mixed leucocyte reaction, PWM.AMLR) was used as a measure of immune hyperreactivity for comparison of atopic with non-atopic individuals. Accordingly, 10/24 non-atopics responded in the PWM.AMLR, and 19/19 atopics reacting to inhaled allergens responded. Autologous stimulation was associated with release of mitogenic factors from the PWM-activated stimulating cells (2/15 non-atopics, 9/15 atopics). For non-atopics, stimulation delivered by staphylococcus A (SAC)-activated cells was similar to that delivered by PWM-induced cells, while in atopics, the SAC.AMLR was never more than 50% of the PWM.AMLR, indicating a possible T cell component. Separation by panning of the stimulation cells into lymphocyte subsets supported the notion that stimulation involved a cooperation between B and T4+ T cells. It is proposed that a positive PWM.AMLR is dependent upon an initial B cell activation followed by the PWM stimulus dependent upon a previous T cell activation, where atopics have more lymphocytes in an activated state than healthy non-atopics. Such a baseline priming may contribute to an innate sensitivity of atopics to environmental allergens.