Lymphokine Synthesis Research Articles

Intravenous immune globulin affects cytokine production in T lymphocytes and monocytesjmacrophages

Immune globulin for intravenous use (IVIG) has been used in many inflammatory conditions due to its immunomodulatory potential. The effector mechanisms are incompletely understood. This study dealt with the effects of IVIG on cytokine production in vitro. Cytokine synthesis was identified at the single-cell level using cytokine-specific MAb and indirect immunocytochemical techniques. Peripheral blood mononuclear cells (PBMC) were stimulated for 96 h by immobilized anti-CD3 MAb or by a combination of a protein kinase C activator (PMA) and a calcium ionophore (ionomycin). The addition of IVIG (6 mg/ml) caused a marked inhibition of proliferation and blast transformation despite unaffected cell survival. Anti-CD3-stimulated cultures containing IVIG exhibited a significant inhibition of production of T-cell derived lymphokines IL-2, IL-10, TNF-beta, IFN-gamma and TNF-alpha (made by both monocytes and T cells), while synthesis of the monokine IL-8 was significantly increased. The expression of IL-2 receptors was significantly suppressed. Similar but transient inhibition of most T-cell products (IL-2, IL-3, IL-4, IL-5, IL-10, TNF-beta and GM-CSF) was noted in the PMA/ionomycin-containing cultures. In contrast, no effects were found on IFN-gamma or TNF-alpha production. The superantigen streptococcal pyrogenic exotoxin-A (SPE-A) induced vigorous cell activation and extensive cytokine synthesis. IVIG was added either at the beginning or 24 h after the initiation of cultures in order to elucidate the importance of direct toxin-neutralization. Addition of IVIG from the beginning of cultures induced a strong reduction of blast transformation and an almost complete inhibition of lymphokine production, in particular of IFN-gamma and TNF-beta. Supplementation with IVIG 24 h after initiation of cultures also led to a significant decrease in lymphokine synthesis. Monokine production (IL-1 alpha, IL-1 beta, IL-1ra, IL-6 and IL-8) was either unaffected or even increased. These two facts argue against direct antigen-neutralization as being the only mechanism at work. However, in IVIG-exposed PBMC stimulated with LPS, IL-6 production was significantly reduced. A significant upregulation of IL-1ra was noticed in unstimulated PBMC cultured with IVIG. The results in all the experiments did not indicate a cytotoxic effect by IVIG on cell survival and the production of certain cytokines were unaffected. Instead, the authors believe that the results suggest a previously little examined functional link where the humoral immune response may have direct immunoregulatory effects on the cellular immune system.

Defective expression of early activation genes in cartilage-hair hypoplasia (CHH) with severe combined immunodeficiency (SCID).

Cartilage-hair hypoplasia (CHH) is an autosomal recessive disease of unknown etiology characterized by metaphyseal dysostosis, unpigmented hair, and defective cellular immunity. We studied peripheral blood mononuclear cells (PBMC) of a boy with CHH and combined immunodeficiency in an attempt to characterize further the immune defect in this disease. Stimulation of his PBMC with mitogens was associated with severely depressed IL-2 and interferon-gamma (IFN-gamma) synthesis and IL-2 receptor alpha-chain (IL-2R alpha) expression and resulted in poor lymphocyte proliferation that was only modestly upregulated by the addition of recombinant IL-2 (rIL-2). The defective proliferation and lymphokine synthesis were not corrected by the addition of phorbol myristate acetate (PMA) and ionomycin, agents that bypass receptor-mediated signalling, indicative of a distal abnormality. Importantly, the levels of mRNA encoding c-myc, IL-2R alpha, IL-2 and IFN-gamma were markedly decreased in patient lymphocytes stimulated with PMA+ionomycin as compared to control lymphocytes. The defect in the expression of these early activation genes was selective in that induction by mitogens of mRNA encoding other early activation gene products such as c-fos and c-jun was not impaired. These results suggest that the underlying defect in this patient and perhaps others with CHH may be an abnormality in a component of intracellular signalling pathways or in a trans-acting factor which regulates the expression of a selected number of early activation genes.

Expression and functional role of 1F7 (CD26) antigen on peripheral blood and synovial fluid T cells in rheumatoid arthritis patients.

The expression and the functional role of the CD26 (1F7) T cell surface molecule, an ectoenzyme which seems to represent a functional collagen receptor of T lymphocytes and to have a role in T cell activation, were analysed in both peripheral blood (PB) and synovial fluid (SF) T cell samples from patients with active and inactive rheumatoid arthritis (RA). Although patients with active disease displayed higher percentages of PB CD26+ CD4+ T cells than inactive RA and control subjects, CD26 antigen expression on RA SF T lymphocytes was low. The anti-1F7 binding to the T cell surface, that led to CD26 antigen modulation and enhancement of both IL-2 synthesis by, and 3H-TdR incorporation of, anti-CD3- or anti-CD2-triggered PB T cells in RA and control subjects, was unable to affect significantly both expression and functional activity of RA SF T lymphocytes. Since the 1F7 antigen spontaneously reappeared on the surface of unstimulated SF T cells after 2-5 days of culturing, the low 1F7 antigen expression of anti-1F7 in the SF T cell compartment may be the result of in vivo molecule modulation exerted by the natural ligand in the joint, with important implications for T cell activation and lymphokine synthesis.

Increased expression of lymphocyte-derived cytokines in benign hyperplastic prostate tissue, identification of the producing cell types, and effect of differentially expressed cytokines on stromal cell proliferation.

Benign prostatic hyperplasia (BPH) frequently exhibit infiltration of CD4 (+)/CD45RO (+) memory-T-lymphocytes. Expression and impact of lymphocyte-derived growth factors on prostatic stromal cell (PSC) growth were investigated. METHODS; Lymphokine synthesis in normal prostate tissues (n = 3), BPH-tissues (n = 13), BPH-derived T-cells (n = 6), BPH-derived epithelial cells (BPH-EC) (n = 5), normal prostate-derived (n = 3) and BPH-derived stromal cell lines (BPH-SC) (n = 6), and prostate cancer (CaP) lines (n = 3) was analyzed by RT-PCR and Southern-blotting. The effect of interleukin (IL)-2, -4, -7, and interferon-gamma (IFN-gamma) on normal and BPH-SC growth was investigated by (3)H-thymidine incorporation assays. All BPH-tissues and, to a lesser degree, normal prostates, expressed significant amounts of IFN-gamma mRNA. However, only BPH-tissues contained IL-2 and IL-4 mRNA (ratio: 10:13). BPH-T-cell lines were heterogeneous in composition and expressed significant amounts of IFN-gamma, IL-2, and IL-4 mRNA. Low level expression of these lymphokines was also observed in BPH-EC, CaP lines, and PSC lines. IL-2, -7 and IFN-gamma stimulated the proliferation of BPH-PSC lines but not that of normal PSC, while IL-4 inhibited BPH-PSC growth. Chronic inflammation may induce an increased growth pattern of fibromuscular tissue in BPH similar to that of wound healing.

Single cell analysis of cytokine expression kinetics by human CD4+ T-cell clones during activation or tolerance induction.

Exposure to optimal peptide antigen concentrations induces human CD4+ T-cell clones to proliferate and secrete various cytokines. Higher (> 10-fold optimal) antigen concentrations cause long-term proliferative unresponsiveness, which can be reversed by exogenous interleukin-2 (IL-2). We call this condition 'tolerance'. We used intracellular cytokine staining and flow cytometric analysis to investigate the kinetics of interferon-gamma, tumour necrosis factor-alpha, IL-4 and IL-5 production during the initial phase of tolerance induction. Single cell analysis of interferon-gamma and IL-4 or IL-5 coexpression showed functional heterogeneity of cloned human CD4+ T cells. Superstimulation with phorbol 12-myristate 13-acetate and ionomycin (PI) revealed enhanced responsiveness shortly after tolerizing treatment, followed by reduced responsiveness. Both tolerized and activated T cells had similarly reduced cytokine responses when further stimulated with antigen during the following 48 hr, with limited enhancement following additional stimulation with PI. We conclude that cytokine induction is normally followed by a refractory phase, but that the expression of cytokines is enhanced in the initial phase of tolerance induction.

Pityrosporum species as a cause of allergy and infection.

Pityrosporum species as a cause of allergy and infection.

T-cell reactivity and its predictive role in immunosuppression after burns.

To obtain further insight into the constitutional, phenotype-dependent changes of T-helper-1 and T-helper-2 signature lymphokine synthesis after trauma. Prospective, descriptive study. Intensive care unit of a burn center in a community hospital. Ten patients 1, 3, 5, and 7 days after major burn injury and 15 healthy individuals. Peripheral blood mononuclear cells were separated and incubated (5 hrs) for cytokine production induced by the accessory cell-independent stimulus of ionomycin and phorbol 12-myristate 13-acetate. After fixation and permeabilization, cell samples were immunofluorescently stained for cell surface antigens (CD4 and CD8), intracellular interferon (IFN)-gamma, and interleukin (IL)-4 synthesis. Results were correlated with corresponding enzyme-linked immunosorbent assay measurements of the culture supernatants. The phenotypic analysis of the composition of the helper (CD4) and suppressor/cytotoxic (CD8) T-cell subset demonstrated that patients suffering from major burns and healthy controls express these antigens in similar percentages. The ratio of CD4 positive to CD8 positive/CD16 negative T-cell subsets showed no significant changes after trauma compared with controls. The production of IL-4 was excessively up-regulated while the release of IFN-gamma was only slightly increased. The predominant cell source of IL-4 after burn trauma was the CD8+ cell with nearly five-fold increased production on day 5 (7.2+/-2.6%) vs. 1.5+/-0.4% in controls. While CD8+ cells are also capable of enhancing their IFN-gamma synthesis under stress by about 60% due to the significant participation of the naive CD45RA+ subset, the CD4+ IFN-gamma release remained largely unchanged. With this study, we demonstrated that in nonsurvivors the number of CD8+ IL-4-producing cells was significantly higher compared with controls; also, the number of IFN-gamma-releasing memory/effector CD45RO+ cells was lower compared with survivors. In previous experiments, we show that a shift to T(H)2 dominated phenotypes increases the risk for postburn infection. The current study confirms that major burns induce a significant shift of cytokine response in the T(H)2 direction and demonstrates that the CD8+, rather than the CD4+ phenotype, is present. Increased IL-4 production is associated with the T(H)2 lymphocyte. These diagnostic tests may help to differentiate patients with compensatory anti-inflammatory response syndrome and immunosuppression from those patients in the proinflammatory state associated with the systemic inflammatory response syndrome. The profile described in this article is associated with immunosuppression and may contraindicate attempts at anti-inflammatory therapy for sepsis.

Monocyte Chemoattractant Protein-1 Synthesis by Murine Lung Fibroblasts Modulates CD4+ T Cell Activation

This study addressed the role of endogenous monocyte chemoattractant protein-1 (MCP-1) in Ag-stimulated lymphokine synthesis and proliferation by CD4+ T cells during their coculture with purified lung fibroblasts or splenic macrophages. Initial experiments showed that fibroblasts exposed to IL-4, TNF alpha, or IL-4 and TNF-alpha (all at 10 ng/ml) for 24 h released five- to eightfold more MCP-1 than similarly treated splenic macrophages. In 72-h coculture experiments, the synthesis of IL-4 by OVA-activated CD4+ T cells added to lung fibroblasts or splenic macrophages was significantly inhibited when endogenous MCP-1 was neutralized using polyclonal anti-MCP-1 antiserum. In these same cocultures, IFN-gamma levels were significantly enhanced. Similarly, IFN-gamma levels were significantly enhanced in 72-h cocultures of a purified peptide derivative-activated CD4+ Th1 clone and lung fibroblasts or splenic macrophages following immunoneutralization of MCP-1. In separate experiments, the selective inhibition of MCP-1 synthesis by lung fibroblasts and splenic macrophages using an MCP-1 antisense oligonucleotide significantly enhanced the proliferation of CD4+ T cells during a 96-h coculture. Taken together, these data suggest that MCP-1 exerts an immunomodulatory effect on CD4+ T cell-derived IL-4 and IFN-gamma release and CD4+ T cell proliferation during cell-to-cell interactions.

Down-regulation of lymphokine synthesis by intravenous gammaglobulin is dependent upon accessory cells.

We have investigated one mechanism by which pooled human IgG preparations for intravenous use (i.v.Ig) selectively down-regulates lymphokine synthesis. Effects of i.v.Ig on cytokine production were quantified at a cellular level by using an immunocytochemical staining technique. Pure T-lymphocyte preparations (from the peripheral blood of healthy adults) were separated by the use of magnetic beads and were then used in parallel experiments with unfractionated mononuclear cells (MNC). Cell activation was induced either by a combination of the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), and the calcium ionophore, ionomycin, or by direct ligation of the T-cell receptor, using immobilized anti-CD3 monoclonal antibody (MoAb). Cells were cultured in the presence or absence of i.v.Ig and subsequently harvested and stained for the following cytokines: interleukin-2 (IL-2), interferon-gamma (IFN-gamma), tumour necrosis factor-beta (TNF-beta) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Assessment of the frequencies of positively stained cells was performed by manual microscopy and by computerized image analysis. Activation by PMA/ionomycin or by immobilized anti-CD3 MoAb induced substantial lymphokine production in both MNC and in purified T cells. Addition of i.v.Ig led to a diminished synthesis of all of the T-cell products studied in unfractionated MNC preparations, whereas production was maintained or occasionally increased in the purified T-cell preparations. These findings indicate that the immunomodulatory effect by i.v.Ig on T-cell activation and lymphokine production was dependent on accessory cells.

Postburn constitutional changes in T-cell reactivity occur in CD8+ rather than in CD4+ cells.

Impairment of T-helper cell function and polarization toward T-helper 2-type cytokine synthesis have been postulated to represent a major cause for posttraumatic immunodeficiency. With a recently developed technology for intracellular cytokine measurement, a new diagnostic tool has become available to discriminate, within hours, a shift of functionality in T-cell subsets via their individual cytokine profiles. Thus, it was the objective of this study to obtain further insight into the constitutional, phenotype-dependent changes of T-helper 1 (TH1) and T-helper 2 (TH2), respectively, signature lymphokine synthesis under traumatic stress. Peripheral blood mononuclear cells from 10 patients with major burn injury on day 1, 3, 5, and 7 after injury and from 15 healthy individuals were separated and incubated (5 hours) for cytokine production induced with the accessory cell-independent stimulus of ionomycin and phorbol 12-myristate 13-acetate. After fixation and permeabilization, cell samples were immunofluorescently stained for cell surface antigens (CD4 and CD8) as well as for intracellular interferon (IFN)-gamma and interleukin (IL)-4 synthesis. Results were correlated with corresponding enzyme-linked immunosorbent assay measurements of the culture supernatants. Phenotypic assessment of peripheral blood mononuclear cells showed a continuously diminished percentage of CD8+ cells during the immediate posttraumatic course compared with controls, whereas the number of CD4+ cells was found to be within the range of the control group. The production of IL-4, the index cytokine of TH2 cells, was excessively up-regulated (from 437.8 +/- 137.0 pg/mL on day 1 to 1,333.6 +/- 532.7 pg/mL on day 7 burns vs. 82.3 +/- 15.8 pg/mL controls), whereas the release of IFN-gamma, the index cytokine of TH1 cells, however, was only slightly increased. The predominant cellular source of IL-4 after burn trauma has been shown to be the CD8+ cell with a nearly fivefold elevated production on day 5 (7.2 +/- 2.6%) versus 1.5 +/- 0.4% in controls. Although CD8+ cells are also capable of enhancing their IFN-gamma synthesis under stress by about 60%, the CD4+ IFN-gamma release remained largely unchanged. Our data corroborate that major burn trauma will induce a significant shift of cytokine response toward the TH2 direction and demonstrate that the CD8+ rather than the CD4+ phenotype is the crucial cell for the polarization toward a TH2-driven immune response.

Immunoregulatory genes and immunosuppression by glucocorticoids.

Glucocorticoids (GCs) are physiological inhibitors of inflammatory responses and are widely used as immunosuppressive and anti-inflammatory agents. GCs induce (i) lymphocyte apoptosis (Cohen, 1989, Galili, 1983) and (ii) inhibit synthesis of lymphokines (Arya et al., 1984, Culpepper and Lee, 1985, Knudsen et al., 1987, Wang et al., 1993, Zanker et al., 1990) and cell surface molecules (Von Knebel et al., 1990) required for immune function. In spite of the widespread use of GCs, the molecular mechanisms that underlie their therapeutic effects are poorly understood.

Immunoregulatory genes and immunosuppression by glucocorticoids

Glucocorticoids (GCs) are physiological inhibitors of inflammatory responses and are widely used as immunosuppressive and anti-inflammatory agents. GCs induce (i) lymphocyte apoptosis (Cohen, 1989, Galili, 1983) and (ii) inhibit synthesis of lymphokines (Arya et al., 1984, Culpepper and Lee, 1985, Knudsen et al., 1987, Wang et al., 1993, Zanker et al., 1990) and cell surface molecules (Von Knebel et al., 1990) required for immune function. In spite of the widespread use of GCs, the molecular mechanisms that underlie their therapeutic effects are poorly understood.

CD26 Surface Molecule Involvement in T Cell Activation and Lymphokine Synthesis in Rheumatoid and Other Inflammatory Synovitis

T cell surface expression and the functional role of CD26 antigen (Ag), a surface ectoenzyme involved in T cell activation and migration across the extracellular matrix, were analyzed in the peripheral blood (PB) and synovial fluid (SF) from patients with inflammatory arthritides. CD26 membrane expression on T cells was detected by cytofluorometry using two different monoclonal antibodies, anti-Ta1 and anti-1F7, while cell proliferation and both IL-2 and IFN-γ production were evaluated in anti-CD3- or anti-CD2-stimulated cell cultures after Ag surface modulation with anti-1F7. The results showed that Ta1 and 1F7 Ag expression were increased on T cells from PB of patients with active, but not inactive, rheumatoid arthritis (RA). Most SF T cells from RA or other inflammatory arthritides displayed the memory marker CD45R0 and the Ta1 Ag, but lacked the 1F7 molecule. In addition,in vitro1F7 modulation, which enhanced RA PB T cell proliferation and both IL-2 and IFN-γ synthesis, did not synergize with anti-CD3 or anti-CD2 in inducing IL-2-dependent activation of SF T cells, but reduced IFN-γ production. A spontaneous reappearance of 1F7 Ag on the SF T cell surface was seen after 2–5 days in culture. Phorbol myristate acetate, able to accelerate its reexpression, also restored a normal response of SF T cells to anti-1F7 comitogenic effects. These data confirm a role of the CD26 surface molecule in regulating T cell activation and lymphokine synthesis. This observation may have important implications in the regulation of T cell activity at the joint level during chronic inflammatory processes.

Specific T-cell tolerance may reflect selective activation of lymphokine synthesis.

Selective T-cell unresponsiveness, as measured by interleukin 2 (IL-2) synthesis upon challenge with antigen, was induced in SJL mice by ovalbumin (OVA) in incomplete or complete Freund's adjuvant administered i.p. or s.c. Ten days later, the mice were given booster injections of 100 micrograms of OVA/complete Freund's adjuvant. On day 20, lymph node and spleen cells were challenged in vitro with serial dilutions of OVA. There was an antigen-specific dose-dependent down regulation of IL-2 production and T-cell proliferation in lymph node T cells. Concomitantly, 100 micrograms of OVA up regulated IL-4 and, to a lesser extent, interferon gamma (IFN-gamma) production, particularly by spleen T cells. Altogether, these data indicate that the drop of IL-2 production and T-cell proliferation, as well as the up regulation of IL-4 and IFN-gamma production, are complex manifestations of an evolving T-cell response. The maturation of the T-cell response leads to the production of different patterns of lymphokines, which may be significantly affected, as desired, by dosage, timing, and route of immunization, as well as by the choice of adjuvants.

THE INHIBITORY EFFECT OF CYCLOPHOSPHAMIDE-INDUCED MAC-1+ NATURAL SUPPRESSOR CELLS ON IL-2 AND IL-4 UTILIZATION IN MLR

Treatment of adult mice with high doses of the immunosuppressive drug cyclophosphamide (CY) induces transient splenic natural suppressor (NS) cell activity mediated largely by cells bearing the MAC-1+ cell-surface marker. Here we show that culture supernatants from mixed lymphocyte reactions (MLR) suppressed by MAC-1+ NS cells exhibit decreased IL-2 and IL-4 activity in bioassays for these lymphokines. However, inhibition of MLR was maximal whether the regulatory cells were added at initiation of culture or 24 hr postinitiation, suggesting that inhibition of lymphokine synthesis is not likely to be the reason for diminished lymphocyte proliferation, since these particular lymphokine genes are known to be transcribed and expressed during the first 12 hr of culture. Furthermore, flow cytofluorometric analysis demonstrated that the presence of MAC-1+ NS cells did not alter the percentage of lymphokine-producing CD4+ T cells in MLR. IL-2 receptor (p55) expression was also normal in suppressed MLR. The addition of exogenous IL-2 and/or IL-4 to MLR failed to reverse the inhibitory effect of MAC-1+ NS cells on lymphocyte proliferation, indicating that these regulatory cells block the utilization of these lymphokines in MLR. The inhibitory effect of MAC-1+ NS cells on lymphocyte proliferation in MLR is dependent on interferon-gamma, since NS activity was dramatically decreased in the presence of neutralizing antibodies to interferon-gamma. MAC-1+ NS cell-induced suppression of MLR was also diminished in the presence of indomethacin, suggesting that prostaglandins play a role in this NS system.

Antigen-independent activation of naive and memory resting T cells by a cytokine combination.

We investigated whether human resting T cells could be activated to proliferate and display effector function in the absence of T cell receptor occupancy. We report that combination of interleukin 2 (IL-2), tumor necrosis factor alpha, and IL-6 activated highly purified naive (CD45RA+) and memory (CD45RO+) resting CD4+ T cells to proliferate. Under this condition, memory resting T cells could also display effector function as measured by lymphokine synthesis and help for immunoglobulin production by B cells. This novel Ag-independent pathway of T cell activation may play an important role in vivo in recruiting effector T cells at the site of immune response and in maintaining the clonal size of memory T cells in the absence of antigenic stimulation. Moreover, cytokines can induce proliferation of naive T cells without switch to memory phenotype and this may help the maintenance of the peripheral pool of naive T cells.

A unique pattern of lymphokine synthesis is a characteristic of certain antigen-specific suppressor T cell clones.

We report that the lymphokines (IFN-gamma) and IL-10 are co-synthesized by previously described CD3+ TCR alpha beta+, minor antigen-specific suppressor T cell clones. IFN-gamma and IL-10 are known to (i) be characteristically produced by different helper T cell types, Th1 and Th2 respectively, and (ii) inhibit the function of the reciprocal subset of T cells: IFN-gamma inhibits the function of Th2 and IL-10 that of Th1 cells. Although Th0 cells are also known to synthesize cytokines of both the Th1- and Th2-type T cells, the suppressor T cells described in this report are different from Th0 cells in that they produce (i) neither IL-2 nor IL-4 molecules and (ii) stimulation via their CD3-TCR system seems independent of both IL-2 and IL-4, the typical autocrine molecules for T cell proliferation. The lymphokine profile of these suppressor T (Ts) cell clones, as well as those of human antigen-specific Ts cells reported earlier, suggests that co-synthesis of some Th1-like and some Th2-like cytokines may be a characteristic of antigen-specific Ts cells as opposed to the type of reciprocal inhibition mediated through IFN-gamma or IL-10, which is antigen non-specific.

T cell-dependent B cell activation.

B cells obtain help from T cells in the antibody response by acting as antigen-specific antigen presenting cells. A direct signal through binding of antigen to membrane Ig can enhance B cell antigen presentation and T-dependent B cell activation, but is not required for a productive interaction between a small resting B cell and a differentiated helper T cell. As a result of helper T cell recognition of antigen on the B cell surface, the T cell becomes activated and in turn activates the B cell. T cell help has two components: lymphokines which act as growth and differentiation factors for B cells, and additional signals which require cell contact and enable B cells to respond to lymphokines. Contact help activity is regulated like lymphokine synthesis and secretion. Because contact help activity is retained by fixed, activated helper T cells and plasma membranes prepared from activated T cells, contact help is likely to be owing to new proteins expressed as membrane-bound lymphokines or activation antigens on helper T cells. Once induced, contact help can be delivered to B cells independently of recognition of antigen/class II MHC. A newly identified activation antigen of helper T cells, a ligand for the B cell differentiation antigen, CD40, is a key component of contact help. The roles of other T and B cell membrane molecules in contact help are reviewed.

Lol p I-induced IL-4 and IFN-γ production by peripheral blood mononuclear cells of atopic and nonatopic subjects during and out of the pollen season

The reciprocal effects of IL-4 and IFN-γ on IgE synthesis have been well established. It has also been shown that these two lymphokines are secreted by different subsets of CD4 + T cells (T H1 and T H2), and that T H2 helper T lymphocytes could be involved in the pathophysiology of allergic diseases. But little is known about the effects of an allergen on the profile of lymphokine synthesis by human peripheral blood mononuclear cells (PBMCs) of allergic and nonallergic subjects. We studied the production of IL-4 and IFN-γ by PBMCs of atopic and nonatopic donors after in vitro stimulation by the group 1 allergen from Lolium perenne pollen ( Lol p I), during and out of the grass pollen season. On natural exposure to pollen, Lol p I-induced IL-4 production was observed only with atopic donors (6 of 8), whereas the synthesis of IFN-γ was observed for all nonatopic donors (7 of 7) and most allergic patients (5 of 7). At the time of the study, higher amounts of IFN-γ were produced by PBMCs of nonatopic donors than by PBMCs of atopic patients. Out of the pollen season the production of IL-4 was not observed either by atopic ( n = 11) or by nonatopic subjects ( n = 5). On the other hand, IFN-γ was produced by PBMCs of most subjects (atopic, 10 of 11; nonatopic, 5 of 5), but at the time of the study no difference was observed between the two groups. These results show that Lol p I induces different profiles of IL-4 and IFN-γ production by PBMCs of atopic and nonatopic subjects. In atopic subjects this profile of lymphokine synthesis is influenced by the natural exposure to pollen, which is in keeping with the seasonal rise of IgE antibodies.

Immunosuppressive effect induced by Actinobacillus actinomycetemcomitans: effect on immunoglobulin production and lymphokine synthesis.

The soluble sonicated extract (SE) from Actinobacillus actinomycetemcomitans inhibited primary T cell-dependent antibody responses in vivo. The production of IgG and IgM to sheep red blood cells (SRBC) was depressed when mice were treated with high concentrations of SE plus SRBC. Preinjection of SE 3 days prior to SRBC completely inhibited IgG production. SE plus SRBC-primed mice showed markedly depressed CD4/CD8 ratios relative to phosphate-buffered saline plus SRBC- or SRBC-immunized mice. SE-sensitized mice showed low blastogenic activity to concanavalin A (Con A) depending on sensitized periods induced by SE. This inhibitory mechanism was, in part, clarified by a suppression of IL-2 synthesis, IL-2 receptor expression and IL-6 secretion by the splenic T cells stimulated with Con A. These results support the hypothesis that the severe infection of A. actinomycetemcomitans suppresses the immune response by affecting CD4/CD8 ratios, followed by lymphokine production and finally antibody responses.