Regulatory T Cells Developing Peri-Weaning Are Continually Required to Restrain Th2 Systemic Responses Later in Life.

Atopic disorders including allergic rhinitis, asthma, food allergy, and dermatitis, are increasingly prevalent in Western societies. These disorders are largely characterized by T helper type 2 (Th2) immune responses to environmental triggers, particularly inhaled and dietary allergens. Exposure to such stimuli during early childhood reduces the frequency of allergies in at-risk children. These allergic responses can be restrained by regulatory T cells (Tregs), particularly Tregs arising in the gut. The unique attributes of how early life exposure to diet and microbes shape the intestinal Treg population is a topic of significant interest. While imprinting during early life promotes the development of a balanced immune system and protects against immunopathology, it remains unclear if Tregs that develop in early life continue to restrain systemic inflammatory responses throughout adulthood. Here, an inducible deletion strategy was used to label Tregs at specified time points with a targeted mechanism to be deleted later. Deletion of the Tregs labeled peri-weaning at day of life 24, but not before weaning at day of life 14, resulted in increased circulating IgE and IL-13, and abrogated induction of tolerance towards new antigens. Thus, Tregs developing peri-weaning, but not before day of life 14 are continually required to restrain allergic responses into adulthood.

Suppression of T lymphocyte activation by 3-chloro-1,2-propanediol mono- and di-palmitate esters in vitro.

This study investigated whether and how 3-chloro-1,2-propanediol (3-MCPD) fatty acid esters, a group of food contaminants formed during processing, might inhibit the immune system through suppressing T lymphocyte activation for the first time. Three 3-MCPD esters including 1-palmitoyl-3-chloropropanediol (1-pal), 2-palmitoyl-3-chloropropanediol (2-pal), and1,2-dipalmitoyl-3-chloropropanediol (dipal) were selected as the probe compounds to test the possible effects of fatty acid structure on their potential immune inhibitory effect. The results showed that 1-pal and 2-pal, but not dipal, significantly suppressed ConA-induced T lymphocyte proliferation, cell cycle activity, Th1 and Th2 cytokine secretion, CD4+ T cell populations, and the ratio of CD4+/CD8+ T cells under the experimental conditions. Moreover, Western blotting and immunofluorescence analyses revealed that 1-pal and 2-pal could inhibit the activation of ConA-stimulated mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways. In addition, 1-pal significantly suppressed DNFB-induced delayed-type hyper sensitivity (DTH) reaction characterized by the increased ear thickness and IFN-γ production in mice. These observations indicated that 3-MCPD esters exerted a negative effect on T lymphocyte-mediated immunity, and the immunosuppressive activities of 3-MCPD monopalmitates were stronger than 3-MCPD dipalmitate.

Red meat allergy induced by tick bites: A Norwegian case report.

SUMMARY: Food allergies, especially delayed hypersensitivity reactions, are often challenging for both patients and clinicians. Here, we report the case of a 64-year-old man who had allergic reactions six hours after eating a meal containing red meat. He reported that he had several tick bites in months before the reaction. High serum specific IgE levels of alpha-gal confirmed the diagnosis of alpha-gal allergic reaction with delayed onset after red meat ingestion caused by tick bite.

Phyllanthin from Phyllanthus amarus inhibits cellular and humoral immune responses in Balb/C mice.

BACKGROUND: Phyllanthin found in many Phyllanthus species has various biochemical and pharmacological properties especially on its hepatoprotective effects. However, its effect on the immune system has not been well documented. PURPOSE: In the present study, phyllanthin isolated from Phyllanthus amarus was investigated for its immunosuppressive effects on various cellular and humoral immune responses in Balb/C mice. METHODS: Male mice were treated daily at 20, 40 and 100mg/kg of phyllanthin for 14 days by oral gavage. The effects of phyllanthin on cellular immune responses in treated /non treated mice were determined by measuring CD 11b/CD 18 integrin expression, phagocytosis, nitric oxide (NO) production, myeloperoxidase activity (MPO), T and B cells proliferation, lymphocyte phenotyping, serum cytokines production by activated T-cells and delayed type hypersensitivity (DTH). Its effects on humoral immune responses were evaluated by determining the serum levels of lysozyme and ceruloplasmin, and immunoglobulins (IgG and IgM). RESULTS: Phyllanthin dose-dependently inhibited CD11b/CD18 adhesion, the engulfment of E. coli by peritoneal macrophages molecules, NO and MPO release in treated mice. Phyllanthin caused significant and dose-dependent inhibition of T and B lymphocytes proliferation and down-regulation of the Th1 (IL-2 and IFN-γ) and Th2 (IL-4) cytokines. Phyllanthin at 100mg/kg caused a significant reduction in the percentage expression of CD4+ and CD8+ in splenocytes and the inhibition was comparable to that of cyclosporin A at 50mg/kg. At 100mg/kg, phyllanthin also dose-dependently exhibited strong inhibition on the sheep red blood cell (sRBC)-induced swelling rate of mice paw in DTH. Significant inhibition of serum levels of ceruloplasmin and lysozyme were observed in mice fed with higher doses (40 and 100mg/kg) of phyllanthin. Anti-sRBC immunoglobulins (IgM and IgG) antibody titer was down-regulated in immunized and phyllanthin-treated mice in a dose-dependent manner with maximum inhibition being observed at 100mg/kg. CONCLUSION: The strong inhibitory effects of phyllanthin on the cellular and humoral immune responses suggest that phyllanthin may be a good candidate for development into an effective immunosuppressive agent.

Carissa congesta Wight and Benincasa hispida (Thunb.) Cogn. as budding immunomodulatory agents.

Carissa congesta and Benincasa hispida are well-known medicinally important plants associated with diabetes, inflammation, protozal infections and cancer. Here, we emphasized up on the immunomodulatory potential of these plants as the source of lupeol, P-sitosterol and ursolic acid. Petroleum ether extracts of C. congesta roots and B. hispida seeds were subjected to acute toxicity studies. They were screened for its immunomodulatory prospective in rats by Haemagglutination Antibody (HA) titre and Delayed-Type Hypersensitivity (DTH) response using Sheep Red Blood Cells (SRBCs of-0.5x109) as antigens. Carbon Clearance test (Phagocytic Index) was estimated by Indian ink suspension. Complete Freund's Adjuvant (CFA) induced arthritis model interpretation was done by paw edema, kene joint erosion (transverse section), body weights, arthritic index and biochemical levels (RBC, WBC and Hb levels). Both the extracts were found to be therapeutically safe up to 5000 mg/kg. Dosage of 100 mg/kg was not satisfactory; and 500 and 250 mg/kg showed significant immunostimmulation (HA Titre) and immunosuppression (DTH response, 48 h). Benincasa hispida seed and Carissa congesta root extracts showed phagocytic Index of 0.0163±0.003, 0.0145±0.003 and 0.0183±0.003, 0.0176±0.003 at 250 mg/kg and 500 mg/kg, respectively. CFA model revealed that the B. hispida seed and C. congesta root extracts decreased paw volume, knee joint erosion, increased body weights and biochemical parameters with an arthritic index of 1.31±0.12, 1.44±0.15 and 1. 16±0.09, 1.36±0.13 at 250 mg/kg and 500 mg, respectively. The results were interpreted by One- way ANOVA followed by Dunnett test. Extracts showed relevance as promising immunostimulators as compared to control.

An unusual case of delayed-type hypersensitivity to ceftriaxone and meropenem.

Recent studies have demonstrated a low cross-reactivity between ß-lactam antibiotics and carbapenems in IgE-mediated reactions. There are no studies on cross-reactivity of meropenem in patients with non-immediate hypersensitivity to cephalosporins. We describe a case of a 13-year-old male, admitted in Neurosurgery with a severe extradural empyema complicating frontal sinusitis, submitted to an emergent bifrontal craniotomy. A generalized maculopapular exanthema, fever and malaise, appeared by the 7th day of meningeal doses of ceftriaxone, clindamycin and vancomycin. Those were replaced by meropenem, with posterior worsening of the reaction and mucosal involvement. A new scheme with amikacin, metronidazole and linezolid was done with improvement. Skin prick, intradermal and patch tests to penicillins, ceftriaxone and meropenem were negative. Lymphocyte transformation test was positive to ceftriaxone and negative to meropenem.Non-immediate T cell mechanism seems to be involved. Diagnosis work-up couldn't exclude cross-reactivity between ceftriaxone and meropenem.

Delayed hypersensitivity reaction resulting in maculopapular-type eruption due to entecavir in the treatment of chronic hepatitis B.

Several clinical trials have demonstrated the potent antiviral efficacy of entecavir (ETV), and this relatively new nucleoside analogue drug has rapidly become a frequently prescribed therapy for chronic hepatitis B (CHB) worldwide. While the studies have also shown a good overall safety profile for ETV, adverse drug reactions (ADRs) in patients with advanced cirrhosis have been reported and represent a broad spectrum of drug-induced injuries, including lactic acidosis, myalgia, neuropathy, azotemia, hypophosphatemia, muscular weakness, and pancreatitis, as well as immune-mediated responses (i.e., allergic reactions). Cutaneous ADRs associated with ETV are very rare, with only two case reports in the publicly available literature; both of these cases were classified as unspecified hypersensitivity allergic (type I) ADR, but neither were reported as pathologically proven or as evaluated by cytokine release analysis. Here, we report the case of a 45-year-old woman who presented with a generalized maculopapular rash after one week of ETV treatment for lamivudine-resistant CHB. The patient reported having experienced a similar skin eruption during a previous three-month regimen of ETV, for which she had self-discontinued the medication. Histopathological analysis of a skin biopsy showed acanthotic epidermis with focal parakeratosis and a perivascular lymphocytic infiltrate admixed with interstitial eosinophils in the papillary and reticular dermis, consistent with a diagnosis of drug sensitivity. A lymphocyte stimulation test showed significantly enhanced IL-4, indicating a classification of type IVb delayed hypersensitivity. The patient was switched to an adefovir-lamivudine combination regimen and the skin eruption resolved two weeks after the ETV withdrawal. This case represents the first pathologically and immunologically evidenced ETV-induced delayed type hypersensitivity skin reaction reported to date. Physicians should be aware of the potential, although rare, for cutaneous ADRs associated with ETV treatment.

Placental restriction of fetal growth reduces cutaneous responses to antigen after sensitization in sheep.

Prenatal and early childhood exposures are implicated as causes of allergy, but the effects of intrauterine growth restriction on immune function and allergy are poorly defined. We therefore evaluated effects of experimental restriction of fetal growth on immune function and allergic sensitization in adolescent sheep. Immune function (circulating total red and white blood cells, neutrophils, lymphocytes, monocytes, eosinophils, and basophils, and the antibody response to Clostridial vaccination) and responses to house dust mite (HDM) allergen and ovalbumin (OVA) antigen sensitization (specific total Ig, IgG1, and IgE antibodies, and cutaneous hypersensitivity) were investigated in adolescent sheep from placentally restricted (PR, n = 23) and control (n = 40) pregnancies. Increases in circulating HDM-specific IgE (P = 0.007) and OVA-specific IgE (P = 0.038) were greater in PR than control progeny. PR did not alter total Ig, IgG1, or IgM responses to either antigen. PR increased OVA-specific but not HDM-specific IgA responses in females only (P = 0.023). Multiple birth increased Ig responses to OVA in a sex-specific manner. PR decreased the proportion of positive cutaneous hypersensitivity responders to OVA at 24 h (P = 0.030) but had no effect on cutaneous responses to HDM. Acute wheal responses to intradermal histamine correlated positively with birth weight in singletons (P = 0.023). Intrauterine growth restriction may suppress inflammatory responses in skin downstream of IgE induction, without impairment in antibody responses to a nonpolysaccharide vaccine. Discord between cutaneous and IgE responses following sensitization suggests new mechanisms for prenatal allergy programming.

Delayed hypersensitivity reaction after initial dose of infliximab: a case report.

We report here an unusual case of delayed hypersensitivity reaction in a young woman with ulcerative colitis after the first administration of infliximab (IFX). The patient developed severe serum-sickness-like reaction, and her anti-IFX antibody titer increased rapidly after a single infusion of IFX. The possible reason for the delayed hypersensitivity reaction to a single IFX exposure might be the presensitization of the patient by murine antigens as she had been keeping mice and hamsters as pets for several years.

Humoral and cellular immunity in chromium picolinate-supplemented lambs.

The effects of oral supplementation of chromium picolinate (CrPic) on humoral and cellular immunity in sheep were investigated. Twenty-four male lambs divided into four treatments and received different dosages of CrPic: placebo (0), 0.250, 0.375, and 0.500 mg of chromium/animal/day during 84 days. The base ration was Panicum maximum cv Massai hay and concentrate. Blood samples were collected fortnightly for total and differential leukocyte counts. On days 28 and 56, the lambs were challenged with chicken ovalbumin I.M. Serum samples were collected on days 46 and 74 and subjected to an indirect enzyme-linked immunosorbent assay to measure IgG anti-ovalbumin. The cell-mediated immune response was determined by a delay-type hypersensitivity test using phytohemagglutinin. CrPic did not significantly affect humoral immunity in lambs but there was a negative effect on cellular immunity (P < 0.05) as Cr supplementation increased. Therefore, the level of Cr supplementation for lambs must be better studied to address its effect on stressed animals or the possible toxic effects of Cr on the animal itself or its immune system.

Partial deficiency of sphingosine-1-phosphate lyase confers protection in experimental autoimmune encephalomyelitis.

BACKGROUND: Sphingosine-1-phosphate (S1P) regulates the egress of T cells from lymphoid organs; levels of S1P in the tissues are controlled by S1P lyase (Sgpl1). Hence, Sgpl1 offers a target to block T cell-dependent inflammatory processes. However, the involvement of Sgpl1 in models of disease has not been fully elucidated yet, since Sgpl1 KO mice have a short life-span. METHODOLOGY: We generated inducible Sgpl1 KO mice featuring partial reduction of Sgpl1 activity and analyzed them with respect to sphingolipid levels, T-cell distribution, and response in models of inflammation. PRINCIPAL FINDINGS: The partially Sgpl1 deficient mice are viable but feature profound reduction of peripheral T cells, similar to the constitutive KO mice. While thymic T cell development in these mice appears normal, mature T cells are retained in thymus and lymph nodes, leading to reduced T cell numbers in spleen and blood, with a skewing towards increased proportions of memory T cells and T regulatory cells. The therapeutic relevance of Sgpl1 is demonstrated by the fact that the inducible KO mice are protected in experimental autoimmune encephalomyelitis (EAE). T cell immigration into the CNS was found to be profoundly reduced. Since S1P levels in the brain of the animals are unchanged, we conclude that protection in EAE is due to the peripheral effect on T cells, leading to reduced CNS immigration, rather than on local effects in the CNS. SIGNIFICANCE: The data suggest Sgpl1 as a novel therapeutic target for the treatment of multiple sclerosis.

Predictors of delayed-type hypersensitivity to Candida albicans and anti-Epstein-Barr virus antibody among children in Kilimanjaro, Tanzania.

We evaluated sex, age, nutritional status, and infectious disease (ID) as predictors of two biomarkers of cell-mediated immunity (CMI), delayed-type hypersensitivity to Candida albicans (DTH-Candida), and anti-Epstein-Barr virus antibody (EBV Ab), among 200 children in Kilimanjaro, Tanzania. DTH-Candida, which decreases with compromised CMI, was positively associated with age (OR: 1.27; 95% CI: 1.02, 1.57) and triceps skinfold (TSF; OR: 1.16; 95% CI: 1.02, 1.26), and inversely associated with height-for-age Z score (HAZ; OR: 0.86; 95% CI: 0.68, 1.08) and diagnosed ID (OR: 0.48; 95% CI: 0.22, 1.08). There was significant interaction between TSF and ID: DTH-Candida exhibited a strong inverse association with ID among children with low TSF (OR: 0.16; 95% CI: 0.05, 0.50) and a strong positive association with TSF among children with ID (OR: 2.64; 95% CI: 1.29, 5.42). EBV Ab, which increases with compromised CMI, was inversely associated with male sex (ß: -0.47; 95% CI: -0.70, -0.24) and TSF (ß: -0.04; 95% CI: -0.08, 0.00), and positively associated with HAZ (ß: 0.06; 95% CI: -0.03, 0.15). Among males, EBV Ab was positively associated with anemia. Among normal HAZ children, EBV Ab was inversely associated with TSF. There was no association between DTH-Candida and EBV Ab. While DTH-Candida provides a direct measure of CMI, our results suggest that interpretation of EBV-Ab among Kilimanjaro children was complicated by its indirect relationship with CMI. Among our sample, CMI increased with age and adequate nutrition and was compromised during acute ID. The suggestive CMI-compromising effect of increasing height-for-age may bear further exploration.

Immunoadjuvant activity of icariin that induces Th1-type antibody in mice.

The adjuvant effect of icariin from Epimedium koreanum on the immune responses to bovine serum albumin (BSA) in mice was examined. Mice were immunized on days 1 and 22 intraperitoneally (i.p.) with one of the following: an emulsion form of BSA mixed with Incomplete Freund's Adjuvant (BSA/IFA) or with Complete Freund's Adjuvant (BSA/CFA) or BSA plus icariin mixed with IFA (BSA/Icariin/IFA). One week after the booster, polyclonal sera were collected from these animals to determine IgG isotypes specific for BSA in the sera and then spleens of these animals were harvested to evaluate IFN-γ and IL-4 produced in the splenocyte cultures. In order to determine the DTH (delayed type hypersensitivity) response, BSA was administered into the footpads of mice that were immunized as described above and the degree of footpad-swelling was measured. Data from these experiments showed that the icariin combined with BSA (BSA/Icariin/IFA) provoked the most abundant of IgG production in mice and enhanced the Th1-lineage development of IgG2a and IFN-γ productions (p < 0.05), whereas BSA/IFA resulted in a highest ratio of IgG1 to IgG2 and most dominant IL-4 production, indicating a Th2 response. This pattern of immunity was confirmed by the DTH determination revealing that icariin-containing formula caused the highest footpad-swelling followed by BSA/CFA and BSA/IFA, respectively. In addition, hemolytic assay showed that icariin at a dose of 1000 µg/mL caused no hemolysis when compared with a water-treated mouse. All of these data indicate that icariin has the immunoadjuvant effect which may enhance Th1-immune response, suggesting that icariin as an adjuvant would be beneficial in the treatment of Th1-disordered diseases.

[Three cases with high TARC levels of gastrointestinal food allergies in neonates and infants].

We measured serum TARC (Thymus and activation-regulated chemokine, CCL-17) levels in three patients of gastrointestinal food allergies in neonates and infants. Patient 1: 14-day-old girl. The chief complaints were poor feeding and weight loss. She tested peripheral eosinophilia (5820 /µL), high serum TARC levels (4730 pg/mL) and positive milk-specific IgE (1.53 UA/mL) at the time of onset. After change from cow' milk formula to hydrolyzed infant formulas and breast milk ahead of dairy products intake, the symptoms resolved. One month and a half later, she re-tested negative milk-specific IgE and normal serum TARC levels (198 pg/mL). Patient 2: 3-month-old girl. The chief complaint was vomiting after intake of cow' milk formula. She tested negative milk-specific IgE and very high serum TARC levels (25200 pg/mL) at the time of onset. After changing to hydrolyzed infant formulas and breast milk ahead of dairy products intake, the symptom resolved. Three months later, she re-tested positive milk-specific IgE (0.42 UA/mL) and normal serum TARC levels (1250 pg/mL). Patient 3: 21-day-old boy. The chief complaint was vomiting after intake of cow' milk formula. He tested peripheral eosinophilia (2923 /µL), very high serum TARC levels (49100 pg/mL) and positive milk-specific IgE (0.47 UA/mL) at the time of onset. After changing to hydrolyzed infant formulas and breast milk ahead of dairy products intake, the symptom resolved. Two weeks later, he re-tested negative milk-specific IgE and serum TARC levels (2210 pg/mL). Serum TARC may be related to the part of gastrointestinal food allergies in neonates and infants.

Immunomodulatory and antioxidant effect of Leptadenia reticulata leaf extract in rodents: possible modulation of cell and humoral immune response.

CONTEXT: Leptadenia reticulata Linn. (Asclpiadaceae) commonly known as "dodi," is an Indian medicinal plant which is known to have ethno-medical uses such as stimulant, tonic, immunostimulant and is one of the ingredient in ayurvedic formulation called as "Chawanprash," which is widely used in India to increase the strength of immune system. OBJECTIVE: The aim of present study is to evaluate immunomodulatory and antioxidant activity of ethanolic extract of L. reticulata L. leaves in rodents. METHODS: Haemagglutinating antibody (HA) titre, haematological profile (Hb, WBC, RBC), lipid peroxidation (LPO), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), delayed type of hypersensitivity (DTH) response, neutrophil adhesion test and carbon clearance assay were determined by in vivo experiments. RESULTS: The evaluation of immunomodulatory potential of L. reticulata (100, 200 mg/kg, p.o.) evoked a significant dose-dependent increase in antibody titre values; DTH reaction induced by SRBC and potentiated percentage neutrophil adhesion to nylon fibers as well as phagocytosis in carbon clearance assay. Also it caused significant increase in haematological profile, GSH, SOD, CAT activity and significantly decreased LPO levels in cyclophosphamide-induced immunosuppressed rats. CONCLUSION: The results obtained in this study indicate that L. reticulata possesses potential immunomodulatory and antioxidant activity and can play a major role in reducing the risk to develop immunodeficiency disorders.

Sphingolipids as new biomarkers for assessment of delayed-type hypersensitivity and response to triptolide.

BACKGROUND: Hypersensitivity diseases are associated with many severe human illnesses, including leprosy and tuberculosis. Emerging evidence suggests that the pathogenesis and pathological mechanisms of treating these diseases may be attributable to sphingolipid metabolism. METHODS: High performance liquid chromatography-tandem mass spectrometry was employed to target and measure 43 core sphingolipids in the plasma, kidneys, livers and spleens of BALB/c mice from four experimental groups: control, delayed-type hypersensitivity (DTH) model, DTH+triptolide, and control+triptolide. Orthogonal partial least squares discriminant analysis (OPLS-DA) was used to identify potential biomarkers associated with variance between groups. Relationships between the identified biomarkers and disease markers were evaluated by Spearman correlation. RESULTS: As a treatment to hypersensitivity disease, triptolide significantly inhibit the ear swelling and recover the reduction of splenic index caused by DTH. The sphingolipidomic result revealed marked alterations in sphingolipid levels between groups that were associated with the effects of the disease and triptolide treatment. Based on this data, 23 potential biomarkers were identified by OPLS-DA, and seven of these biomarkers correlated markedly with the disease markers (p<0.05) by Spearman correlation. CONCLUSIONS: These data indicate that differences in sphingolipid levels in plasma and tissues are related to DTH and treatment with triptolide. Restoration of proper sphingolipid levels may attribute to the therapeutic effect of triptolide treatment. Furthermore, these findings demonstrate that targeted sphingolipidomic analysis followed by multivariate analysis presents a novel strategy for the identification of biomarkers in biological samples.

Cellular and humoral immune responses after short-term oral hormone therapy in postmenopausal women.

OBJECTIVE: To evaluate the cellular and humoral immune responses after oral hormone therapy in postmenopausal women. Study design This was a prospective cohort study, with intervention. The main outcome measures were delayed-type IV cell-mediated hypersensitivity, leukocytes, immunoglobulins, interleukin-6 (IL-6) and interleukin-10 (IL-10). METHODS: The delayed-type cell-mediated hypersensitivity was measured by using five common allergens before and after 3 months of hormone therapy. Each type of leukocyte cell was counted before and after hormone therapy. Different subtypes of lymphocytes were determined by flow cytometry. Immunoglobulins G, A and M were measured by nephelometry; immunoglobulin E was measured by electrochemiluminescence. IL-6 and IL-10 concentrations were determined by chemiluminescence. RESULTS: Hormone therapy increased the response to tuberculin antigen without changing the total number of leukocytes, eosinophils, neutrophils, lymphocytes, and CD4 +, CD8 + B cells. Both monocyte number and CD4 + /CD8 + ratio suffered a slight modification (p = 0.057). Immunoglobulins A, M and E remained unchanged and immunoglobulin G decreased (p = 0.029). IL-6 levels remained stable but IL-10 concentrations increased significantly after hormone therapy. CONCLUSION: Short-term oral hormone treatment has no impact on the cellular immune response but, concerning the humoral immune response, immunoglobulin G decreased and the levels of IL-10 were significantly higher.

Flow cytometric analysis of lymphocyte proliferative responses to food allergens in dogs with food allergy.

Two different allergy tests, antigen-specific immunoglobulin E quantification (IgE test) and flow cytometric analysis of antigen-specific proliferation of peripheral lymphocytes (lymphocyte proliferation test), were performed to examine differences in allergic reactions to food allergens in dogs with food allergy (FA). Thirteen dogs were diagnosed as FA based on clinical findings and elimination diet trials. Seven dogs clinically diagnosed with canine atopic dermatitis (CAD) were used as a disease control group, and 5 healthy dogs were used as a negative control group. In the FA group, 19 and 33 allergen reactions were identified using the serum IgE test and the lymphocyte proliferation test, respectively. Likewise, in the CAD group, 12 and 6 allergen reactions and in the healthy dogs 3 and 0 allergen reactions were identified by each test, respectively. A significant difference was found between FA and healthy dogs in terms of positive allergen detection by the lymphocyte proliferation test, suggesting that the test can be useful to differentiate FA from healthy dogs but not from CAD. Both tests were repeated in 6 of the dogs with FA after a 1.5- to 5-month elimination diet trial. The IgE concentrations in 9 of 11 of the positive reactions decreased by 20-80%, whereas all the positive reactions in the lymphocyte proliferation test decreased to nearly zero (P<0.05), suggesting that lymphocytes against food allergens may be involved in the pathogenesis of canine FA.