High fat diet-induced maternal obesity in mice impairs peripartum maternal behaviour.

Obesity during pregnancy represents a significant health issue and can lead to increased complications during pregnancy and impairments with breastfeeding, along with long-term negative health consequences for both mother and offspring. In rodent models, diet-induced obesity (DIO) during pregnancy leads to poor outcomes for offspring. Using a DIO mouse model, consisting of feeding mice a high fat diet for 8 weeks before mating, we recapitulate the effect of high pup mortality within the first 3 days postpartum. To examine the activity of the dam around the time of birth, late pregnant control and DIO dams were recorded in their home cages and the behaviour of the dam immediately before and after birth was analysed. Prior to giving birth, DIO dams spent less time engaging in nesting behaviour, while after birth, DIO dams spent less time in the nest with their pups compared to control dams, indicating reduced pup-engagement in the early postpartum period. We have previously reported that lactogenic hormone action, mediated by the prolactin receptor, in the medial preoptic area of the hypothalamus (MPOA) is critical for the onset of normal postpartum maternal behaviour. We hypothesized that DIO dams may have lower lactogenic hormone activity during late pregnancy, which would contribute to impaired onset of normal postpartum maternal behaviour. Day 16 lactogenic activity, transport of prolactin into the brain, and plasma prolactin concentrations around birth were all similar in control and DIO dams. Moreover, endogenous pSTAT5, a marker of prolactin receptor activity, in the MPOA was unaffected by DIO. Overall, these data indicate that lactogenic activity in late pregnancy of DIO dams is not different to controls and is unlikely to play a major role in impaired onset of normal postpartum maternal behaviour.

Regulatory T cells and allergic asthma.

Because of the characteristic airway inflammation observed in allergic asthma, the pathogenesis of this disease may be due, in part, to a lack of anti-inflammatory and immune suppressive mechanisms. Here, we discuss the possible involvement and therapeutic use of T regulatory cells and their soluble factors in this multifactorial disease.

Evaluation of fiber-composite laminate in the restoration of immature, nonvital maxillary central incisors.

The purpose of this study was to evaluate the use of fiber-composite laminate, a reinforcement ribbon embedded throughout a composite restoration, to reinforce immature maxillary central incisors. Twenty-six mature maxillary central incisors were prepared a minimum of 3 mm below the facial cementoenamel junction to simulate immature nonvital teeth. They were separated into 3 groups: group 1 was unfilled and served as a control; group 2 was filled to the depth of the preparation with composite; and group 3 was filled with composite and Connect Reinforcement Ribbon. The specimens were subjected to class I loading in an Instron Testing Machine until catastrophic failure occurred. The results indicate a highly significant difference between the groups (p < or = 0.003). Group 1 fractured at an average load of 31.08 kg, group 2 at 51.00 kg, and group 3 at 37.93 kg. These findings suggest that composite alone increases fracture resistance of the immature tooth model more than composite with Reinforcement Ribbon.

Phenotypic characterization of human CD4+ regulatory T cells obtained from cutaneous dinitrochlorobenzene-induced delayed type hypersensitivity reactions.

In this study, we describe the generation and characterization of cloned human CD4+ T lymphocyte populations that have infiltrated into cutaneous, 2,4-dinitrochlorobenzene-induced delayed type hypersensitivity reactions in healthy human subjects. It is shown that, in addition to T helper type 1 clones, elevated numbers of regulatory T clones, producing high levels of interleukin-10 and interleukin-5, but no measurable interleukin-4, were isolated from delayed type hypersensitivity reactions in four of six donors. A subsequent challenge with 2,4-dinitrochlorobenzene of two donors from whom only few interleukin-10-producing T cell clones had been generated after primary challenge, resulted in a decrease in the frequency of T helper type 1 clones and a strong increase in the number of interleukin-10-producing T helper type 2 and regulatory T clones. Culture supernatants from the latter cells, activated with anti-CD3 and anti-CD28 monoclonal antibody, inhibited alloantigen-mediated T cell proliferation which was, partly dependent on interleukin-10, and independent of transforming growth factor-beta. In addition, dendritic cells generated in vitro in the presence of these culture supernatants were impaired in their ability to induce alloantigen-induced proliferative responses. Differential expression of transcripts for the T1/ST2 molecule enabled a phenotypic distinction between resting regulatory T cells and T helper type 2 cells, but not between regulatory T cells and T helper type 1 cells. This experimental model provides a useful tool to isolate human inflammatory and anti-inflammatory T cell subpopulations and, furthermore, enables the study of the kinetics of their appearance into delayed type hypersensitivity reactions.

Pityrosporum and Candida specific and non-specific humoral, cellular and cytokine responses in atopic dermatitis patients.

BACKGROUND: Recent cytokine (RT-PCR, ELISA) analyses of inflammation in atopic dermatitis (AD) have suggested a role for IL-4, IL-5 and IFNgamma. Pityrosporum ovale and Candida albicans are important allergens in some patients with AD of the seborrhoic head, neck and shoulder region. In AD patients, the saprophytic yeasts induce IgE responses while they usually induce TH1 type responses. The cytokine responses induced by yeasts in AD are sparsely investigated. OBJECTIVE: To characterize the P. ovale- and C. albicans-specific and non-specific humoral, lymphoproliferative and cytokine (IL-2, 4, 5 and IFNgamma) responses in AD. METHODS: Fifteen AD patients and seven healthy controls (HC) were included. Ficoll-isolated PBMC were stimulated by PHA and laboratory-generated extracts of P. ovale and C. albicans. Lymphocyte proliferation was measured by 3H-thymidine incorporation and cytokine production by sandwich-ELISAs. The antigen-specific IgG and IgE antibodies were analysed by ELISA and nitrocellulose RAST. RESULTS: Pityrosporum ovale- and C. albicans-specific IgE (both P < 0.001) and P. ovale-induced PBMC proliferation (P < 0.02) were elevated in AD. In general, the IL-4/IFNgamma ratio induced by P. ovale was higher than that induced by C. albicans (P < 0.01). The PHA-induced IL-2 (P < 0.05) and IL-4 responses (P < 0.005), and the C. albicans-induced IL-5 response (P < 0.02) and IFNgamma response (P < 0.01), were elevated in AD. A network of correlations was seen between serum total and the yeast-specific IgE, P. ovale-specific lymphoproliferation, PHA-induced IL-2, IL-4 and IL-5, and C. albicans-induced IL-5. CONCLUSION: The cytokine profiles found in this study support the role of TH0 or TH1 cells by the side of TH2 cells in the pathogenesis of atopic dermatitis. Pityrosporum ovale appears to be associated more with IL-4 responses and C. albicans with IFNgamma responses.

Cytokines and cell surface molecules independently induce CXCR4 expression on CD4+ CCR7+ human memory T cells.

In the present study, we show that IL-2, IL-4, IL-7, and IL-15 are able to induce functional CXCR4 surface expression on resting in vitro-generated CD4+ CXCR4- CCR7+ memory T cells. Cytokine-mediated induction of CXCR4 expression was associated with an increase in CXCR4 transcription, enhanced stromal-derived factor-1-induced T cell migration in vitro, and increased susceptibility of these cells to infection with X4 strains of HIV-1. CXCR4 expression could also be induced through an alternative pathway, following coculture of these cells with CD40-activated, autologous, CD34+ progenitor-derived dendritic cells. Although these dendritic cells express transcripts for IL-7 and IL-15, addition of neutralizing anti-IL-7R and IL-15 mAbs did not block induction of CXCR4 expression. Indeed, dendritic cell-mediated up-regulation of CXCR4 expression was found to depend on CD40/CD154 and CD134/CD134L interactions. Whereas activated autologous dendritic cells induced the expression of both CXCR4 and CD25 on a portion of CCR7+ memory T cells, concomitant CD3-mediated activation of these cells further enhanced CD25 expression, but, in contrast, prevented induction of CXCR4 expression. This observation suggests that triggering of the CD134 and CD154 molecules, in contrast to TCR/CD3 complex-mediated stimulation, results in simultaneous T cell activation and CXCR4 expression. Taken together, these results show that common gamma-chain-interacting cytokines as well as signals mediated via noncognate interactions between activated dendritic cells and memory T cells are involved in the up-regulation of CXCR4 expression.

TCR-mediated activation of allergen-specific CD45RO(+) memory T lymphocytes results in down-regulation of cell-surface CXCR4 expression and a strongly reduced capacity to migrate in response to stromal cell-derived factor-1.

The selective migration of functional T(h) lymphocyte subsets with different cytokine production profiles into inflamed tissue is likely to depend on the state of activation of the cells, as well as on the differential expression of various adhesion molecules and chemokine receptors. In this study, we have analyzed the effect of allergen-specific activation on the expression of the chemokine receptor CXCR4 on T lymphocytes. We show that stimulation of peripheral blood mononuclear cells from atopic patients with the allergen Der p results in down-regulation of CXCR4 surface expression on Der p-activated CD25(+)CD45RO(+) antigen-specific memory cells which was caused by a decrease in CXCR4 gene transcription and did not seem to be mediated by endogenous cytokines, such as IFN-gamma. In contrast, however, CXCR4 surface expression was enhanced on naive CD25(-)CD45RO(-) and resting CD25(-)CD45RO(+) memory T cells, as a result of the presence of endogenous IL-4, most likely produced by Der p-activated memory T cells. Antigen-specific CD25(+)CD45RO(+) T lymphocytes, purified 7 days after stimulation with Der p, had a strongly reduced capacity to migrate in response to stimulation with stromal cell-derived factor (SDF)-1, the ligand for CXCR4. Together, these results suggest that differential expression of CXCR4 on activated and resting T cells is due to the counteracting effects of TCR-mediated down-regulation and IL-4-mediated up-regulation of this chemokine receptor respectively, and furthermore indicate that antigen-activated memory T cells are unlikely to migrate into inflamed tissue in response to SDF-1.

Candida albicans mannan- and protein-induced humoral, cellular and cytokine responses in atopic dermatitis patients.

BACKGROUND: The cytokine observed most often in atopic dermatitis (AD) is IL-4, but a role for IL-5 and IFN-gamma in the late and delayed phase reactions has been suggested. In AD with head, neck and shoulder distribution, hypersensitivity to saprophytic yeasts is an important pathogenetic factor. The yeast allergens include both the mannan polysaccharides and the proteins. Mannans are major cross-reacting allergens likely to be involved in the pathogenesis of AD. OBJECTIVE: To characterize the humoral, lymphoproliferative and cytokine (IL-2, 4, 5 and IFN-gamma) responses of peripheral blood mononuclear cells (PBMCs) induced by Candida albicans mannan and protein antigens in AD. METHODS: Fifteen AD patients and seven healthy controls were included. Ficoll-isolated PBMCs were stimulated by PHA and laboratory-generated mannan and protein extracts of C. albicans. Lymphocyte proliferation was measured and cytokine production was studied by ELISA. The antigen-specific IgG and IgE antibodies were analysed by ELISA and nitrocellulose RAST. RESULTS: In AD mannan (P < 0.005) and protein (P < 0.002), specific IgE levels were higher than in healthy controls. Both mannan and protein-specific lymphoproliferations (both: P < 0.02) were higher in AD than in healthy controls. Mannan, but not protein, induced long lasting IL-2 and IL-4 productions from 24 h lasting up to 66-96 h and IL-5 and IFN-gamma productions with elevated levels at 66 and 96 h. The mannan-induced IL-2 (P = 0.015) and IFN-gamma (P < 0.005) were increased in AD as compared with healthy controls. Significant correlations were seen between the protein-induced proliferation responses and both serum total IgE (r = 0.59, P < 0.01) and protein-specific IgE (r = 0.65, P < 0.005). The mannan-induced IL-2 responses correlated with the specific IgE (r = 0.62, P < 0.01) and proliferation (r = 0.51, P < 0.02) and S-IgE level (r = 0.71, P < 0. 002). Mannan-induced IL-4 and IFN-gamma productions also correlated (r = 0.43, P < 0.05). CONCLUSIONS: C. albicans mannan induced elevated IL-2 and IFN-gamma responses in AD patients. The correlations of the cytokine responses with mannan-induced IgE and proliferation responses suggest that C. albicans mannan induced TH1 type cytokine responses are involved in AD.

Identification, cloning and expression of p25, an AT-rich DNA-binding protein from the extreme thermophile, Thermus aquaticus YT-1.

Although the G+C content of Thermus aquaticus YT-1 chromosomal DNA is 67.4%, regions with lower G+C content have also been observed. AT-rich DNA-binding proteins may contribute to the thermostability and biological functions of these DNA regions at Thermus growth temperatures. Using double-stranded DNA (dsDNA)-cellulose chromatography, a T.aquaticus YT-1 protein, designated as p25, was identified to bind preferentially to AT-rich DNA. The gene encoding p25 was cloned and sequenced after immunoscreening T.aquaticus YT-1 expression libraries. The deduced primary structure of p25 is 211 amino acids in length with a molecular weight of 23 225 Da. Native p25 was purified and characterized as a homodimer with modification possibly at lysine and arginine residues. Its preferential and temperature-dependent binding to AT-rich DNA was confirmed with mobility-shift DNA-binding assays. The protein was demonstrated to bind preferentially to dsDNA instead of single-stranded DNA. The binding of p25 to dsDNA also improved the thermotolerence of this protein. Overexpression study of fusion p25 suggested that the N-terminus of the protein might form the DNA-binding domain or be closely involved in DNA-binding activity.

Effect of bronchial allergen challenge on in vitro cytokine release by peripheral blood mononuclear cells of atopic patients.

BACKGROUND: During the pollen season, peripheral blood mononuclear cells (PBMC) from allergic patients produce increased levels of Th2 cytokines after stimulation with allergen in vitro. We have studied the effect of a single bronchial provocation test (BPT) of allergic patients to determine whether allergen challenge in vivo modulates cytokine production by PBMC, after subsequent stimulation with the same allergen in vitro. METHODS: Twelve atopic asthmatic patients were challenged with the relevant allergen, and their PBMC, isolated before (T0) or 6 (T6) or 24 h (T24) after BPT, respectively, were cultured for 120 h in the presence or absence of the same allergen, after which cytokine production was measured by ELISA. RESULTS: Allergen-specific activation of the PBMC at T0 resulted in interleukin (IL)-5 and IL-13 production, but not in detectable levels of interferon-gamma and IL-4. BPT did not induce the secretion of the latter cytokines. However, IL-5 and IL-13 production was significantly decreased at T24, as compared to T0. No statistically significant differences were found between the production of IL-10 before and after BPT. CONCLUSIONS: In contrast to the effects of natural challenge with allergen, a decrease in the production of some Th2 cytokines by peripheral blood T cells was observed 24 h after BPT, suggesting a concomitant decrease in the frequency of allergen-specific T cells in the circulation.

Immunotherapy with Fel d 1 peptides decreases IL-4 release by peripheral blood T cells of patients allergic to cats.

BACKGROUND: Cells producing a T(H2)-cytokine profile play an important role in the onset and maintenance of atopic diseases, and therefore specific immunotherapy is aimed to induce a switch to cells producing a T(H1)- or T(H0)-cytokine profile. Recently, a novel form of immunotherapy making use of synthetic peptides from the major cat allergen Fel d 1 has been developed, but its mechanisms of action are unknown. OBJECTIVES: We examined the effects of immunotherapy with Fel d 1 peptides on the response to bronchial provocation tests (PD20FEV1) with a standardized Fel d 1 cat extract on Fel d 1-specific serum IgE and IgG levels and in vitro IL-4 and IFN-gamma production. METHODS: Patients allergic to cats received 6 weekly injections of 7.5 micro(g) (low dose), 75 micro(g) (medium dose), or 750 micro(g) (high dose) of Fel d 1 peptides (25 patients) or a placebo (6 patients). RESULTS: Six weeks after ending immunotherapy, posttreatment PD20FEV1 was not significantly different between the treated and placebo groups. However, in the medium- and high-dose groups there was a significant improvement between baseline and posttreatment days. IL-4 release was significantly reduced in the high dose-treated group (P <.005, Wilcoxon W test), whereas it was unchanged in the low or medium dose- and in the placebo-treated groups. In all groups, IFN-gamma, IgE, and IgG levels remained unchanged. CONCLUSION: There was no correlation between the improvement of PD20FEV1 and the decrease in IL-4 production. These data suggest that peptide immunotherapy may act by shifting the Fel d 1-induced response of PBMCs in vitro from the T(H2)-like to the T(H0)-like phenotype.

IL-4 induces functional cell-surface expression of CXCR4 on human T cells.

Here we report that IL-4 specifically enhances cell surface expression of CXCR4 on resting peripheral and cord blood T cells. Whereas polarized Th2 clones express variable levels of CXCR4, expression of this receptor is undetectable on polarized Th1 clones but can be induced on the latter cells as well, following short-term culture in the presence of IL-4. The IL-4-induced CXCR4 is functional since interaction with its ligand, stromal-derived factor (SDF)-1, activates the p42 MAP-kinase ERK-2. In addition, although CXCR4 expression is down-regulated following stimulation of T cells and T cell clones via CD28 or CD3 and CD2 cell surface molecules, respectively, it is re-induced by IL-4. These data indicate an important role for IL-4 in rendering CD4+ T cells susceptible to infection with HIV via CXCR4, as well as in promoting SDF-1-induced migration of these cells.

The role of IgE in asthma.

Asthma is a multifactorial and complex disease in which allergic factors and non-allergic triggers interact and result in bronchial obstruction and inflammation. Allergenic sensitization is important in the development of asthma and, although links between inhalant allergy and asthma have been known for many years, they have recently been re-emphasized. Indoor allergens are associated with asthma prevalence, severity and exacerbations whereas outdoor allergens such as pollens are associated with exacerbations. Moreover, there is a link between total IgE and asthma which appears to be independent of allergen sensitization. One of the typical aspects of airway inflammation of asthma is the infiltration of the airway wall by T helper type 2 (Th2) cells. These cells are attracted to inflammatory sites by adhesion molecules and chemokines among which CCR3 and CXCR4 receptors appear to be of importance. Differentiation of B cells into IgE-secreting plasma cells is a complex cascade of events in which cytokines play a crucial role. Both IL-4 and IL-13 are inducing IgE synthesis whereas IFN-gamma and IL-12 are blocking IgE synthesis. IgE production by B cells not only requires the presence of IL-4 or IL-13, but also a physical interaction between T and B cells, involving a number of surface and adhesion molecules such as CD40-CD40L and CD28/CD80. Production of TH2-cytokines is not restricted to T cells as basophils and mast cells can produce them indicating that these cells may be of importance in the synthesis of IgE.

Different modulation by histamine of IL-4 and interferon-gamma (IFN-gamma) release according to the phenotype of human Th0, Th1 and Th2 clones.

Histamine, an important inflammatory mediator in allergic diseases and asthma, has been reported to have modulator effects on T cells, suggesting that the bronchial microenvironment may regulate the function of resident T cells. We examined the effect of histamine on the release of the Th2-associated cytokines IL-4 and IL-5 and the Th1-associated cytokine IFN-gamma by 30 CD4+ T cell clones from peripheral blood or bronchial biopsy of one atopic subject. Based on the IL-4/IFN-gamma ratio, the clones were ascribed to the Th2 (ratio > 1), Th0 (ratio > or = 0.1 and < or = 1) or Th1 (ratio < 0.1) phenotype. Histamine inhibited IFN-gamma production by Th1-like cells (P < 0.02, Kruskall-Wallis), especially from bronchial biopsy, but had no effect on IL-4 release. Regarding Th0 clones, histamine inhibited IL-4 production (P < 0.02) in a dose-dependent manner and slightly inhibited IFN-gamma production, but had no effect on Th2-like cells. Histamine had a heterogeneous and insignificant effect on IL-5 production. The H2-receptor antagonist ranitidine completely reversed the inhibition of IL-4 and IFN-gamma production, whereas the agonist dimaprit mimicked this effect. In contrast, H1- and H3-receptor agonists and antagonists had no significant effect. These data demonstrate that histamine has different effects on IL-4 and IFN-gamma release by T helper cells according to their phenotype via H2-receptors. This study extends the immunomodulatory effects of histamine which may contribute to the perpetuation of airway inflammation in asthma.

Modification of surface marker expression on CD14 monocytes of allergic patients after lysis or Ficoll purification.

It has been observed that peripheral blood monocytes are often in a primed or activated state in inflammatory diseases such as asthma. However, the majority of these studies have been performed using cells which have been purified by density gradient centrifugation on Percoll or Ficoll-Hypaque. Using cytofluorimetry, we compared the expression of monocyte surface markers of monocytes from untreated blood with monocytes purified by erythrocyte lysis or density centrifugation using the Ficoll technique. Monocytes from two groups of subjects were analyzed: healthy subjects and allergic patients. When compared with untreated blood, the percentage of CD16-positive cells, and the sMFI was significantly greater after monocyte purification (lysis or Ficoll). The expression of CD62L (percentage and sMFI) was modified after monocyte purification. Such modification of these two surface markers was predominantly observed on monocytes from allergic patients, and not on monocytes from healthy subjects. This study suggests that surface marker analysis should be performed on unfractionated whole blood in order to avoid modification of monocyte antigens.

Nicotine does not modulate IL-4 and interferon-gamma release from peripheral blood mononuclear cells and T cell clones activated by phorbol myristate acetate and calcium ionophore.

Tobacco smoking induces an increased nonspecific IgE response. IgE synthesis is controlled by IL-4 and IFN-gamma. The effect of nicotine (10(-10) to 10(-5) M), one of the major components of tobacco smoke, were studied on IL-4 and IFN-gamma release by peripheral blood mononuclear cells from 12 allergic patients and 12 nonallergic subjects and 16 T cell clones stimulated by nonspecific agonists (phorbol myristate acetate and calcium ionophore). The release of IL-4 and IFN-gamma was measured by ELISA in supernatants after a 48-hour culture. Nicotine did not modify IL-4 and IFN-gamma release by peripheral blood mononuclear cells or T cell clones. The effects of tobacco smoke on IgE production are unlikely to change in the T cell phenotype by nicotine.

Decreased interleukin-4 and increased gamma interferon production by peripheral blood mononuclear cells of patients with Lyme borreliosis.

Spontaneous and Borrelia burgdorferi-stimulated proliferation of peripheral blood mononuclear cells (PBMCs) and their interleukin-4 (IL-4), gamma interferon (IFN-gamma), and NO production were measured in 36 patients with second- or third-stage Lyme borreliosis (LB) and 11 control subjects. Spontaneous proliferation of PBMCs was significantly higher (P = 0.0003) in the LB patients than in the control subjects. Spontaneous production of IL-4 was significantly lower in patients than in control subjects (P = 0.0007), but spontaneous production of IFN-gamma was slightly higher in patients. The proliferative response of PBMCs to stimulation with B. burgdorferi was significantly higher (P = 0.01) in patients. The B. burgdorferi-induced production of IFN-gamma (P = 0.002) was also significantly higher in patients. The spontaneous and B. burgdorferi-induced production of NO showed no significant difference between patients and control subjects. These findings indicate that the activation of PBMCs in patients with late LB is enhanced in vivo. Furthermore, the production of IL-4 is effectively suppressed spontaneously, whereas the production of IFN-gamma by PBMCs is slightly increased spontaneously and significantly enhanced during stimulation with B. burgdorferi in vitro. The "spontaneous" or disease-induced alterations in cytokine levels of patients, in this case suppression of a Th2-type cytokine production and activation of a Th1-type cytokine production, may contribute to the pathogenesis of LB.

Interleukin-4 and interferon-gamma production by peripheral blood mononuclear cells from food-allergic patients.

The aim of this study was to investigate whether patients with food allergy had a cytokine imbalance of interleukin (IL)-4 and interferon-gamma (IFN-gamma) production. Diagnostic procedures including skin prick tests, determination of food-specific serum IgEs, and positive double-blind, placebo-controlled, food challenges identified 15 adult patients. They were compared with 15 age- and sex-matched healthy subjects. Peripheral blood mononuclear cells (PBMC) were incubated for 24, 48, and 72 h in the presence of phytohemagglutinin plus phorbol myristate acetate. After mitogen stimulation, culture supernatants from patients with food allergy contained significantly less IFN-gamma but increased IL-4 when compared with healthy controls. Secretion of IL-4 was maximal at 24 h and IFN-gamma secretion was maximal at 72 h. There was no correlation between cytokine secretion in vitro and serum IgE level. These findings demonstrated that an imbalance of IL-4 and IFN-gamma production is present in food allergy, as documented in other allergic diseases, but other mechanisms are probably also involved.

Seasonal variations of interleukin-4 and interferon-gamma release by peripheral blood mononuclear cells from atopic subjects stimulated by polyclonal activators.

IgE synthesis is controlled by interleukin (IL)-4 and interferon (IFN)-gamma, but there is heterogeneity in the IL-4 response depending on the sensitization of patients and natural allergen exposure. In patients sensitized to various allergens, we studied the synthesis of IL-4, IFN-gamma, and IgE to determine to what extent their in vitro immune response may be influenced by pollen season, depending on their sensitization. We studied 12 nonallergic individuals, seven patients sensitized to cypress pollen, 12 sensitized to grass pollen, 14 sensitized to several pollens, and 42 patients with polysensitization. The release of IL-4 and IFN-gamma from peripheral blood mononuclear cells stimulated by polyclonal agents (calcium ionophore A23187 and phorbol myristate acetate) was measured by ELISA. The spontaneous and IL-4-induced release of IgE was measured by ELISA. In patients with cypress pollen allergy, IL-4 and IgE release were significantly lower than in patients with other allergies. In the pollen-sensitized group, IL-4 and IgE release were significantly higher during the pollen season than out of it. No variation in IL-4 or IgE release was observed in the polysensitized group. IFN-gamma production was not affected by the pollen season. These data show that the seasonal variations of IL-4 and IgE synthesis differ according to the sensitization of patients.