Toxocara canis extract fractions promote mainly the production of Th1 and regulatory cytokines by human leukocytes in vitro.

Helminths possibly down-modulate immune responses to airborne allergens through the induction of a regulatory network. The identification of helminths bioactive molecules is highly desirable, given their immunomodulatory potential which could be used in immunotherapies for allergy and autoimmune diseases. To investigate the immunoregulatory potential of the adult Toxocara canis crude extract and ten protein fractions of its extract, human peripheral blood mononuclear cells (PBMC) from 10 allergic and 9 non-allergic individuals were cultivated, in vitro, in the presence or absence of these antigens, and their supernatants were evaluated for cytokine production (TGF-ß, IL-10, IL-12, TNF-α, IL-6, IL-5, IL13, and IL-17). To determine the cell viability, the PBMC were cultivated for 24 h in the presence of the antigens and, following, they were subjected to a cytotoxicity assay. The viability of the PBMC was not affected by incubation with the T. canis antigens. As some fractions stimulated the production of immunoregulatory (TGF-ß and/or IL-10), IL-12 and Th1 (TNF-α) cytokines, without stimulating Th2 cytokines (IL-5 and IL13) and IL-17, it was proposed that they would be potential candidates for further studies, especially involving the purification and characterization of specific proteins, which could be tested separately to evaluate their specific role as adjuvants in immunotherapy for inflammatory diseases.

Tolerogenic Dendritic Cells Reduce Cardiac Inflammation and Fibrosis in Chronic Chagas Disease.

Chronic Chagas disease cardiomyopathy (CCC) is the most frequent and severe form of this parasitic disease. CCC is caused by a progressive inflammation in the heart, resulting in alterations that can culminate in heart failure and death. The use of dendritic cells (DCs) appears as an option for the development of treatments due to their important role in regulating immune responses. Here, we investigated whether tolerogenic cells (tDCs) could interfere with the progression of CCC in an experimental model of Chagas disease. The tDCs were generated and characterized as CD11b+ CD11c+ cells, low expression of MHC-II, CD86, CD80, and CD40, and increased expression of PD-L. These cells produced low levels of IL-6 and IL-12p70 and higher levels of IL-10, compared to mature DCs (mDCs). Interestingly, tDCs inhibited lymphoproliferation and markedly increased the population of FoxP3+ Treg cells in vitro, compared to mature DCs. In a mouse model of CCC, treatment with tDCs reduced heart inflammation and fibrosis. Furthermore, tDCs treatment reduced the gene expression of pro-inflammatory cytokines (Ifng and Il12) and of genes related to cardiac remodeling (Col1a2 and Lgals3), while increasing the gene expression of IL-10. Finally, administration of tDCs, increased the percentage of Treg cells in the hearts and spleens of chagasic mice. Ours results show that tolerogenic dendritic cells have therapeutic potential on CCC, inhibiting disease progression.

Erratum: Tolerogenic Dendritic Cells Reduce Airway Inflammation in a Model of Dust Mite Triggered Allergic Inflammation.

This corrects the article on p. 406 in vol. 10, PMID: 29949837.

Tolerogenic Dendritic Cells Reduce Airway Inflammation in a Model of Dust Mite Triggered Allergic Inflammation.

PURPOSE: The use of tolerogenic dendritic cells (TolDCs) to control exacerbated immune responses may be a prophylactic and therapeutic option for application in autoimmune and allergic conditions. The objective of this work was to evaluate the effects of TolDC administration in a mouse model of allergic airway inflammation caused by mite extract. METHODS: Mouse bone marrow-derived TolDCs were induced by incubation with granulocyte-macrophage colony-stimulating factor (GM-CSF) and dexamethasone, and then characterized by flow cytometry and cytokine production by enzyme-linked immunosorbent assay (ELISA). For the in vivo model of Blomia tropicalis-induced allergy, mice transplanted with antigen-pulsed TolDCs were sensitized intraperitoneally with B. tropicalis mite extract (BtE) adsorbed to aluminium hydroxide. After challenge by nasal administration of BtE, bronchoalveolar lavage fluid (BALF), lungs, spleen and serum were collected for analysis. RESULTS: Induction of TolDCs was efficiently achieved as shown by low expression of major histocompatibility complex (MHC) II, programmed death-ligand (PD-L) 2 and pro-inflammatory cytokine production, and up-regulation of interleukin (IL)-10, upon LPS stimulation in vitro. Transplantation of 1 or 2 doses of BtE-pulsed TolDCs reduced the number of inflammatory cells in BALF and lungs as well as mucus deposition. Moreover, compared to saline-injected controls, TolDC-treated mice showed lower serum levels of anti-BtE immunoglobulin E (IgE) antibodies as well as reduced Gata3 and IL-4 gene expression in the lungs and decreased IFN-γ levels in the supernatant of splenocyte cultures Transplantation of TolDCs increased the percentage of the regulatory T cells in the spleen and the lungs. CONCLUSIONS: Preventive treatment with TolDCs protects against dust mite-induced allergy in a mouse model, reinforcing the use of tolerogenic dendritic cells for the management of allergic conditions.

Parasitic load and histological aspects in different regions of the spleen of dogs with visceral leishmaniasis.

Leishmania infantum causes from subclinical infection to severe disease in humans and dogs. The spleen is one of the organs most affected by the infection. Although evidence exists that the parasitic load distribution and histological alterations may not be homogeneous in the affected organs of naturally infected individuals, it has not been formally demonstrated using the current techniques used for studying the disease. In six dogs naturally infected with Leishmania, parasitic load and histological changes were compared in samples collected from the lower, middle and upper third of the spleen. Parasitic load in the spleen of the group of dogs was variable, revealing a difference of 61 times between animals with the lowest and the highest parasitism. The set of parasitic load values of each dog showed a cluster trend, when compared to the other animals. Nevertheless, the parasitic load values of each dog showed a variation ranging from 3.2 to 34.7 times between lowest and highest value. Histological changes showed recognizable variation in frequency (granulomas) or intensity (perisplenitis) in the spleen of 2 out of the 6 dogs. The agreement of histological findings between samples collected from the different thirds of the spleen was good (kappa coeficient, 0.61-0.80) very good (0.81-0.99) or perfect (1.00), for most of the parameters analyzed. Variability of parasitic load and, to a lesser extent, histological changes in spleen of dogs with visceral leishmaniasis is observed. Such variability may be taken in account in the design of studies on pathogenesis, vaccine and therapeutic drug development.

Evaluation of a new set of recombinant antigens for the serological diagnosis of human and canine visceral leishmaniasis.

Current strategies for the control of zoonotic visceral leishmaniasis (VL) rely on its efficient diagnosis in both human and canine hosts. The most promising and cost effective approach is based on serologic assays with recombinant proteins. However, no single antigen has been found so far which can be effectively used to detect the disease in both dogs and humans. In previous works, we identified Leishmania infantum antigens with potential for the serodiagnosis of VL. Here, we aimed to expand the panel of the available antigens for VL diagnosis through another screening of a genomic expression library. Seven different protein-coding gene fragments were identified, five of which encoding proteins which have not been previously studied in Leishmania and rich in repetitive motifs. Poly-histidine tagged polypeptides were generated from six genes and evaluated for their potential for diagnosis of VL by ELISA (Enzyme Linked ImmunoSorbent Assay) with sera from infected humans and dogs. None of those was valid for the detection of human VL (26-52% sensitivity) although their performance was increased in the canine sera (48-91% sensitivity), with one polypeptide useful for the diagnosis of canine leishmaniasis. Next, we assayed a mixture of three antigens, found to be best for human or canine VL, among 13 identified through different screenings. This "Mix" resulted in similar levels of sensitivity for both human (84%) and canine (88%) sera. With improvements, this validates the use of multiple proteins, including antigens identified here, as components of a single system for the diagnosis of both forms of leishmaniasis.

Dissociation between skin test reactivity and anti-aeroallergen IgE: Determinants among urban Brazilian children.

BACKGROUND: The dissociation between specific IgE and skin prick test reactivity to aeroallergens, a common finding in populations living in low and middle-income countries, has important implications for the diagnosis and treatment of allergic diseases. Few studies have investigated the determinants of this dissociation. In the present study, we explored potential factors explaining this dissociation in children living in an urban area of Northeast Brazil, focusing in particular on factors associated with poor hygiene. METHODS: Of 1445 children from low income communities, investigated for risk factors of allergies, we studied 481 with specific IgE antibodies to any of Blomia tropicalis, Dermatophagoides pteronyssinus, Periplaneta americana and Blatella germanica allergens. Data on demographic, environmental and social exposures were collected by questionnaire; serum IgG and stool examinations were done to detect current or past infections with viral, bacterial, protozoan and intestinal helminth pathogens. We measured atopy by skin prick testing (SPT) and specific IgE (sIgE) to aerollergens in serum (by ImmunoCAP). SIgE reactivity to B. tropicalis extract depleted of carbohydrates was measured by an in-house ELISA. Total IgE was measured by in house capture ELISA. SNPs were typed using Illumina Omni 2.5. RESULTS: Negative skin prick tests in the presence of specific IgE antibodies were frequent. Factors independently associated with a reduced frequency of positive skin prick tests were large number of siblings, the presence of IgG to herpes simplex virus, Ascaris lumbricoides and Trichuris trichiura infections, living in neighborhoods with infrequent garbage collection, presence of rodents and cats in the household and sIgE reactivity to glycosylated B. tropicalis allergens. Also, SNP on IGHE (rs61737468) was negatively associated with SPT reactivity. CONCLUSIONS: A variety of factors were found to be associated with decreased frequency of SPT such as unhygienic living conditions, infections, total IgE, IgE response to glycosylated allergens and genetic polymorphisms, indicating that multiple mechanisms may be involved. Our data, showing that exposures to an unhygienic environment and childhood infections modulate immediate allergen skin test reactivity, provide support for the "hygiene hypothesis".

Oxidative stress in sepsis. Possible production of free radicals through an erythrocyte-mediated positive feedback mechanism

Abstract Background: Sepsis is an illness with a high morbidity for which no effective treatment exists. Its treatment has a high cost because it usually requires an intensive care unit and expensive antibiotics. The present study focus in the production of reactive oxygen species in the early stages of sepsis. This study aimed at investigating the production of reactive oxygen specie during the inflammatory response in patients with sepsis. Methods: Reactive oxygen specie production and insoluble myeloperoxidase obtained from fresh whole blood were measured by photon counting chemiluminescence in the blood of 18 septic patients and 12 healthy individuals. Modified red blood cells were evaluated by staining of blood smears. The production of reactive oxygen species by macrophages and polymorphonuclear leukocytes put into contact with modified red blood cells were also assessed by photon counting chemiluminescence. Results: The appearance of oxidatively modified erythrocytes, which is an evidence of oxidative stress, was supported by the detection of reactive oxygen species and insoluble myeloperoxidase in the whole blood of all septic patients. Peroxynitrite was the main reactive oxygen species found in the whole blood. Oxidatively modified erythrocytes activated phagocytic cells in vitro, leading to the considerable production of free radicals. Conclusion: It was found that sepsis led to a high oxidative stress and to extensive modification of erythrocytes. It is proposed that a positive feedback mechanism, involving the activation of circulating leukocytes by these modified erythrocytes would maintain the pro-oxidative state even after the disappearance of bacteria.

Oxidative stress in sepsis. Possible production of free radicals through an erythrocyte-mediated positive feedback mechanism.

BACKGROUND: Sepsis is an illness with a high morbidity for which no effective treatment exists. Its treatment has a high cost because it usually requires an intensive care unit and expensive antibiotics. The present study focus in the production of reactive oxygen species in the early stages of sepsis. This study aimed at investigating the production of reactive oxygen specie during the inflammatory response in patients with sepsis. METHODS: Reactive oxygen specie production and insoluble myeloperoxidase obtained from fresh whole blood were measured by photon counting chemiluminescence in the blood of 18 septic patients and 12 healthy individuals. Modified red blood cells were evaluated by staining of blood smears. The production of reactive oxygen species by macrophages and polymorphonuclear leukocytes put into contact with modified red blood cells were also assessed by photon counting chemiluminescence. RESULTS: The appearance of oxidatively modified erythrocytes, which is an evidence of oxidative stress, was supported by the detection of reactive oxygen species and insoluble myeloperoxidase in the whole blood of all septic patients. Peroxynitrite was the main reactive oxygen species found in the whole blood. Oxidatively modified erythrocytes activated phagocytic cells in vitro, leading to the considerable production of free radicals. CONCLUSION: It was found that sepsis led to a high oxidative stress and to extensive modification of erythrocytes. It is proposed that a positive feedback mechanism, involving the activation of circulating leukocytes by these modified erythrocytes would maintain the pro-oxidative state even after the disappearance of bacteria.

Protective effects of mito-TEMPO against doxorubicin cardiotoxicity in mice.

PURPOSE: Doxorubicin (DOX) is a chemotherapeutic that is widely used for the treatment of many human tumors. However, the development of cardiotoxicity has limited its use. The aim of the present study was to evaluate the possible efficacy of mito-TEMPO (mito-T) as a protective agent against DOX-induced cardiotoxicity in mice. METHODS: C57BL/6 mice were treated twice with mito-T at low (5 mg/kg body weight) or high (20 mg/kg body weight) dose and once with DOX (24 mg/kg body weight) or saline (0.1 mL/20 g body weight) by means of intraperitoneal injections. The levels of malondialdehyde (MLDA), a marker of lipid peroxidation, and serum levels of creatine kinase were evaluated 48 h after the injection of DOX. RESULTS: DOX induced lipid peroxidation in heart mitochondria (p < 0.001), and DOX-treated mice receiving mito-T at low dose had levels of MLDA significantly lower than the mice that received only DOX (p < 0.01). Furthermore, administration of mito-T alone did not cause any significant changes from control values. Additionally, DOX-treated mice treated with mito-T at high dose showed decrease in serum levels of total CK compared to mice treated with DOX alone (p < 0.05). CONCLUSION: Our results indicate that mito-T protects mice against DOX-induced cardiotoxicity.

The anti-allergic activity of Cymbopogon citratus is mediated via inhibition of nuclear factor kappa B (Nf-Κb) activation.

BACKGROUND: The prevalence of allergic diseases such as asthma has significantly increased worldwide, making it a public health concern. There is an urgent need for new anti-inflammatory agents with selective pharmacology and lower toxicity. Plant extracts have been used for centuries in traditional medicine to alleviate inflammatory diseases. In this work, we evaluated the anti-allergic activity of Cymbopogon citratus (Cy), a medicinal herb used by folk medicine to treat asthma. METHODS: We used a murine model of respiratory allergy to the mite Blomia tropicalis (Bt) and evaluated certain parameters known to be altered in this model. A/J mice were sensitized (100 µg/animal s.c.) and challenged (10 µg/animal i.n.) with Bt mite extract and treated with 60, 120 or 180 mg/kg of Cy standardized hexane extract. The parameters evaluated included: cellular infiltrate in bronchoalveolar lavage (BAL); eosinophil peroxidase activity (EPO); histopathological examination of the lung; serum levels of specific IgE, IgG1 and IgG2a; Th2 cytokine concentrations in BAL and expression of NF-κB. RESULTS: Our results showed that oral administration of a Cy hexane extract (especially 180 mg/Kg) reduced the numbers of leukocytes/eosinophils in BAL; the eosinophil peroxidase activity in BAL; the infiltration of leukocytes in lung tissue; the production of mucus in the respiratory tract; the level of IL-4 in BAL and the nuclear expression of NF-κB. CONCLUSIONS: The results presented demonstrate the potential of the Cy hexane extract to modulate allergic asthma; this extract may be an alternative future approach to treat this pathology.

Enhancement of experimental cutaneous leishmaniasis by Leishmania extract: identification of a disease-associated antibody specificity.

BACKGROUND: Both Leishmania braziliensis and Leishmania amazonensis induce cutaneous disease when injected in the skin of BALB/c mice. However, L. amazonensis may also visceralize in that strain of mice, infecting mainly the liver and spleen. In addition, whereas BALB/c mice die with a progressive cutaneous disease when infected by L. amazonensis, the infection by L. braziliensis is spontaneously cured. In a previous work, we have found that intravenous injections of L. amazonensis amastigote extract (LaE) potentiated a L. braziliensis infection in BALB/c mice, and that this infection-promoting activity could be inhibited by the addition of protease inhibitors to the extract. METHODS: In order to detect markers of disease evolution, in the present work we analyzed the specificity of the anti-L. amazonensis antibody response of L. braziliensis-infected BALB/c mice injected intravenously with saline or LaE, supplemented or not with protease inhibitors, by the Western blot technique. RESULTS: IgG1 antibodies recognizing an antigen with apparent molecular weight of 116 kDa were specifically detected in BALB/c mice that had been turned susceptible to L. braziliensis infection by injections of LaE. CONCLUSION: A Th2 immune response (IgG1 antibody-producing) against this 116 kDa antigen, therefore, could be associated with susceptibility to severe Leishmania infection.

Potential therapeutic effect of Allium cepa L. and quercetin in a murine model of Blomia tropicalis induced asthma.

BACKGROUND: Asthma is an inflammatory condition characterized by airway hyperresponsiveness and chronic inflammation. The resolution of inflammation is an essential process to treat this condition. In this study we investigated the effect of Allium cepa L. extract (AcE) and quercetin (Qt) on cytokine and on smooth muscle contraction in vitro and its therapeutic potential in a murine model of asthma. METHODS: AcE was obtained by maceration of Allium cepa L. and it was standardized in terms of quercetin concentration using high performance liquid chromatography (HPLC). In vitro, using AcE 10, 100 or 1000 µg/ml or Qt 3.5, 7.5, 15 µg/ml, we measured the concentration of cytokines in spleen cell culture supernatants, and the ability to relax tracheal smooth muscle from A/J mice. In vivo, Blomia tropicalis (BT)-sensitized A/J mice were treated with AcE 100, 1000 mg/kg or 30 mg/kg Qt. We measured cell influx in bronchoalveolar lavage (BAL), eosinophil peroxidase (EPO) in lungs, serum levels of Bt-specific IgE, cytokines levels in BAL, and lung histology. RESULTS: We observed a reduction in the production of inflammatory cytokines, a relaxation of tracheal rings, and a reduction in total number of cells in BAL and EPO in lungs by treatment with AcE or Qt. CONCLUSION: AcE and Qt have potential as antiasthmatic drugs, as they possess both immunomodulatory and bronchodilatory properties.

IL2RA genetic variants reduce IL-2-dependent responses and aggravate human cutaneous leishmaniasis.

The outcome of Leishmania infections varies substantially, depending on the host and the parasite strain; infection may be asymptomatic or cause mild or severe skin ulcers (cutaneous leishmaniasis [CL]), limited or disseminated lesions, or lethal visceral disease. We previously reported an association between IL-2R mutations and susceptibility to visceral leishmaniasis in children infected with Leishmania donovani. In the present study, we evaluated the possible role of IL-2 signaling in human CL. We first showed that the transcripts of several genes of the IL-2 pathway were abundant in skin lesions caused by Leishmania braziliensis. We then carried out a genetic analysis, focusing on major genes of the IL-2 pathway. We used a family-based approach and found that polymorphisms of several genes appeared to be associated with CL in a Brazilian population. Moreover, two polymorphisms of the IL2RA gene were significantly and independently associated with CL. We confirmed this result in a second Brazilian sample (also exposed to L. braziliensis) and in Iranians infected with Leishmania tropica: IL2RA rs10905669 T (Pcombined = 6 × 10(-7)) and IL2RA rs706778 T (Pcombined = 2 × 10(-9)) were associated with greater susceptibility to lesion development. These alleles were also correlated with a poor IFN-γ response and poor FOXP3(+) regulatory T cell activation. Thus, IL-2 plays a crucial role in protection against the cutaneous ulcers caused by Leishmania, and the IL-2 pathway is a potential target for strategies aiming to control Leishmania-related diseases.

Candidin and trichophytin stimulate the production of Th1 and regulatory cytokines by peripheral blood mononuclear cells: implication for their use as adjuvants in immunotherapy.

AIM: This study's objective was to investigate whether candidin or trichophytin elicit recall immune responses that could potentially inhibit a Th2 response. MATERIALS & METHODS: Peripheral blood mononuclear cells from nine allergic and seven nonallergic individuals were cultivated in vitro in the presence or absence of these fungal extracts. RESULTS: Trichophytin or candidin, or both, stimulated the production of regulatory cytokines (TGF-ß and/or IL-10), accompanied or not by stimulation of production of cytokines associated with the Th1 response (TNF-α, IL-12 and IFN-γ), but without stimulation of Th2 cytokines (IL-5 and IL-13) and IL-17, by peripheral blood mononuclear cells of most allergic and nonallergic individuals. CONCLUSION: These results indicate that these fungal extracts could be used as adjuvants in personalized therapeutic vaccines in a fair proportion of individuals. In addition, they justify the carrying out of investigations aimed at identifying molecules in these extracts that might exclusively induce Treg and/or Th1 immune responses.

Effects of helminth co-infections on atopy, asthma and cytokine production in children living in a poor urban area in Latin America.

BACKGROUND: Helminths are modulators of the host immune system, and infections with these parasites have been associated with protection against allergies and autoimmune diseases. The human host is often infected with multiple helminth parasites and most studies to date have investigated the effects of helminths in the context of infections with single parasite or types of parasites (e.g. geohelminths). In this study, we investigated how co-infections with three nematodes affect markers of allergic inflammation and asthma in children. We selected Ascaris lumbricoides and Trichuris trichiura, two parasites that inhabit the human intestine and Toxocara spp (Toxocara canis and/or T. cati), intestinal roundworms of dogs and cats that cause systemic larval infection in humans. These parasites were selected as the most prevalent helminth parasites in our study population. RESULTS: 36.4% of children were infected with one parasite; 12.7% with 2 and 5.2% with 3. Eosinophilia>4% and >10% was present in 74.3% and 25.5% of the children, respectively. Total IgE>200 IU/mL, sIgE≥0.70 kU/L and SPT positivity were present in 59.7%, 37.1% and 30% of the children, respectively. 22.7% had recent asthma (12.0% non-atopic and 10.7% atopic). Helminth infections were associated in a dose-dependent way to decrease in the prevalence of SPT and increase in eosinophilia, total IgE, and the production of the regulatory cytokine IL-10 by unstimulated peripheral blood leukocytes. No association with asthma was observed. CONCLUSIONS: Helminth co-infections in this population were associated with increased markers of the Th2 immune response, and with a host immune regulatory phenotype that may suppress allergic effector responses such as immediate hypersensitivity reactions in the skin.

Extracellular vesicles from Leishmania-infected macrophages confer an anti-infection cytokine-production profile to naïve macrophages.

BACKGROUND: Extracellular vesicles (EVs) are structures with phospholipid bilayer membranes and 100-1000 nm diameters. These vesicles are released from cells upon activation of surface receptors and/or apoptosis. The production of EVs by dendritic cells, mast cells, macrophages, and B and T lymphocytes has been extensively reported in the literature. EVs may express MHC class II and other membrane surface molecules and carry antigens. The aim of this study was to investigate the role of EVs from Leishmania-infected macrophages as immune modulatory particles. METHODOLOGY/PRINCIPAL FINDINGS: In this work it was shown that BALB/c mouse bone marrow-derived macrophages, either infected in vitro with Leishmania amazonensis or left uninfected, release comparable amounts of 50-300 nm-diameter extracellular vesicles (EVs). The EVs were characterized by flow cytometry and electron microscopy. The incubation of naïve macrophages with these EVs for 48 hours led to a statistically significant increase in the production of the cytokines IL-12, IL-1ß, and TNF-α. CONCLUSIONS/SIGNIFICANCE: EVs derived from macrophages infected with L. amazonensis induce other macrophages, which in vivo could be bystander cells, to produce the proinflammatory cytokines IL-12, IL-1ß and TNF-α. This could contribute both to modulate the immune system in favor of a Th1 immune response and to the elimination of the Leishmania, leading, therefore, to the control the infection.

Requirement of dual stimulation by homologous recombinant IL-2 and recombinant IL-12 for the in vitro production of interferon gamma by canine peripheral blood mononuclear cells.

BACKGROUND: Very few studies have been carried out so far aiming at modulating cellular immune responses in dogs. In this study, we evaluated the ability of recombinant canine IL-2 (rcaIL-2) and IL-12, in the form of a single-chain fusion protein (rsccaIL-12), to stimulate peripheral blood mononuclear cells (PBMC) of healthy mongrel dogs. RESULTS: Recombinant canine IL-2 purified from Escherichia coli or present in the supernatant of COS-7 cells transfected with pcDNA3.1-caIL-2 (COS-7 caIL-2 supernatant) was able to induce proliferation of CTLL-2 cells, thus showing their functional activity. In addition, purified rcaIL-2 and COS-7 caIL-2 supernatant stimulated resting canine PBMC proliferation to a level higher than baseline level. Neither COS-7 sccaIL-12 supernatant nor COS-7 caIL-2 supernatant alone was able to induce significant production of interferon gamma by resting PBMC. However, COS-7 sccaIL-12 supernatant in combination with COS-7 caIL-2 supernatant induced production of IFN-γ by those cells. CONCLUSIONS: The data shown herein suggest that the combination of canine recombinant IL-12 and IL-2 can be useful to promote cellular immune responses in dogs.