Pulmonary Inflammatory Infiltration Research Articles

Gasometria arterial e inflamação pulmonar de ratos com diferentes tempos de sepse abdominal

RACIONAL: Sepse é a principal causa de morbi-mortalidade nas vítimas de trauma e em pacientes cirúrgico e apesar de toda tecnologia e terapêutica disponível não há diminuição nestas estatísticas. OBJETIVOS: Avaliar as repercussões ácido-básicas e o grau de injúria pulmonar decorrentes de sepse abdominal em ratos após seis e 24 horas de peritonite fecal através da ligadura e punção do ceco. MÉTODOS: Foram utilizados 40 ratos Wistar, machos, adultos. A amostra foi dividida aleatoriamente em quatro grupos: grupo A (sham/6 h - n=5) submetidos à laparotomia mediana infra-umbilical sem nenhuma outra intervenção; grupo B (sham/24h - n=5) submetidos à laparotomia mediana infra-umbilical sem nenhuma outra intervenção; grupo C (LPC/6 h - n=15) submetidos à ligadura e punção do ceco e grupo D (LPC/24h - n=15) submetidos à ligadura e punção do ceco. Após seis ou 24 horas, conforme o grupo em estudo, os animais foram novamente anestesiados e submetidos as seguintes análises: observação clínica de sinais de sepse, laparotomia através do mesmo acesso anterior e realização de cultura do líquido peritoneal e punção cardíaca para obtenção de amostra sangüínea suficiente para gasometria arterial, hematócrito e leucometria. Procedeu-se eutanásia e os pulmões retirados para análise de edema pulmonar e o infiltrado inflamatório. RESULTADOS: Ocorreram quatro óbitos no grupo D. Verificou-se, em todos os grupos, a presença de acidose mista. Comparando os grupos experimento 6h versus controle 6h foram encontradas duas variáveis significativas - HCO3 (p=0,0015) e BE (p=0,0015) -, demonstrando acidose metabólica mais grave no grupo experimento. Nos grupos controle também se confirmou acidose mista, devido às alterações das variáveis HCO3 (p=0,0079), PO2 (p=0,0079) e SO2 (p=0,0079). A correlação entre o grau de comprometimento pulmonar e o estado metabólico confirma a existência de resposta inflamatória sistêmica evidenciada por aumento de neutrófilos e hemorragia alveolar difusa nos pulmões do rato séptico. CONCLUSÃO: O modelo de LPC foi método eficaz para indução de sepse. A laparotomia e a manipulação de alças intestinais são fatores desencadeantes de acidose mista em ratos, comprovado pelos resultados da gasometria, que demonstrou ser método confiável na detecção de alterações no metabolismo ácido-básico dos ratos estudados.

Role of mast cell degranulation in the neural correlates of the immediate allergic reaction in a murine model of asthma

Experimental airway allergy in mice leads to increased activity in specific hypothalamic and amygdaloid nuclei, and behavioral changes. The experiments described here were designed to determine the role of anaphylactic antibodies, mast cell degranulation, and lung inflammation in the neural and behavioral correlates of an experimental murine asthma-like response. Animals were sensitized intraperitoneally with ovalbumin adsorbed to alum, and challenged by intranasal ovalbumin instillation or aerosol. To induce immunological tolerance, animals were fed ovalbumin in the drinking water for 5 consecutive days, along with primary sensitization. Depletion of IgE was also accomplished with a non-anaphylactic anti-IgE antibody. Mast cell degranulation was inhibited by cromolyn. In addition to BALB/c animals, C3H/HeJ mice were used for their relative resistance to lung allergic inflammation. We confirmed that ovalbumin challenge in allergic mice leads to increased activity in the paraventricular nucleus of the hypothalamus and central nucleus of the amygdala, and avoidance behavior towards an allergen-associated compartment. Moreover, these responses were precluded by oral tolerance or anti-IgE treatment, even in the presence of IgG1. Cromolyn abrogates both responses in the presence of anaphylactic antibodies. Finally, although sensitized C3H/HeJ mice did not develop airway inflammation, they exhibited brain and behavioral changes similar to BALB/c animals. The repercussions of murine allergic asthma on brain and behavior are IgE-dependent, mediated by mast cell degranulation, and do not require a pulmonary inflammatory infiltrate, suggesting that the early phase of this immediate allergic response suffices for the brain activation associated with avoidance behavior towards exposure to the allergen.

Non-ruptured hydatid cyst can lead to death by spread of cyst content into bloodstream: an autopsy case

Hydatid disease is a parasitic infestation caused by a tapeworm of the genus Echinococcus, and it is common in Mediterranean regions. Cystic lesions cause symptoms via compressing adjacent organs or may be totally silent. Morbidity is usually secondary to free rupture of the echinococcal cyst with or without anaphylaxis, infection of the cyst or dysfunction of affected organs. The cyst of Echinococcus granulosus is commonly located in the liver and frequently causes no symptoms. Anaphylactic reactions as a result of cyst perforation generally occur during interventions such as needle aspiration or open surgery; however, the spillage of cyst fluid with intravascular spread resulting from trauma may also trigger anaphylaxis, and rare case reports of this kind are present in the literature. We report the case of a 17-year-old man who was admitted to the public hospital with a sudden onset of nausea, vomiting and fainting. After a short period of intervention in the emergency department he died. As the cause of his sudden death was unknown, a forensic autopsy was carried out by the Forensic Council of Turkey. The autopsy revealed a macroscopically non-ruptured hydatid cyst in the liver and laryngeal oedema. In histopathological examination, two scolices in the pulmonary artery and inflammatory infiltration mainly composed of mast cells in the larynx were detected. Sudden death in this case was attributed to anaphylactic shock caused by intravascular spread of the cyst contents.

Respiratory syncytial virus induces pneumonia, cytokine response, airway obstruction, and chronic inflammatory infiltrates associated with long-term airway hyperresponsiveness in mice.

Respiratory syncytial virus (RSV) infection is associated with acute morbidity (e.g., pneumonia and airway obstruction [AO]) and long-term complications (e.g., airway hyperresponsiveness [AHR]). We present a comprehensive evaluation of the acute and chronic phases of RSV respiratory tract infection, using a mouse model. BALB/c mice were inoculated with RSV and monitored for 154 days. RSV loads and cytokines were measured in bronchoalveolar lavage (BAL) samples. Pneumonia severity was assessed using a standard histopathologic score, and pulmonary function was determined by plethysmography. RSV-infected mice exhibited viral replication that peaked on day 4-5 and became undetectable by day 7. These mice developed acute pneumonia (peak days, 4-5) and chronic pulmonary inflammatory infiltrates that lasted up to 154 days after inoculation. BAL concentrations of tumor necrosis factor- alpha, interleukin (IL)-6, interferon- gamma, IL-4, IL-10, KC (an IL-8 homologue), MIG (CXCL9), RANTES, macrophage inflammatory protein-1 alpha, and eotaxin were significantly higher in RSV-infected mice than in control mice. RSV-infected mice developed acute AO during the first week of infection that persisted for 42 days. RSV-infected mice also showed significant AHR in response to methacholine up to 154 days. This model provides a means to investigate the immunopathogenesis of RSV infection and its association with reactive airway disease.

Pancreatitis-induced lung injury: mechanism of injury involves hepatic NF-KB and cytokine mediated pathways

Introduction: The liver has been suggested as a source of NF-kB related inflammatory cytokines involved in the regulation of pancreatitis induced lung injury. The mechanisms and timing of this interaction are not well defined. Methods: Severe acute pancreatitis (SAP) was induced in female C57Bl/6 mice by feeding a choline-deficient ethionine supplemented (CDE) diet for 48 hours. They were followed for 96 hours from diet initiation and sacrificed at 12 hour intervals (5 mice per time point). NF- B activation was determined in lung and liver tissue nuclear protein extracts using p65 ELISA (Active Motif). TNF-a, IL-6, MIP-2, and KC levels in liver and lung homogenates were evaluated using the sandwich ELISA method. Results: Pancreatitis was confirmed by elevated plasma amylase and by histologic evidence of injury. Liver NF- B activation was present by 36 hours (p < .05), with IL-6, MIP-2, and KC levels increasing sharply by 72 hours and remained elevated (p < .05). Pulmonary MIP-2 and KC levels were elevated at 72 hours (p < .05), and correlated with increased MPO activity in the lung. Pulmonary chemokine release and inflammatory cell infiltrate were not associated with increased NF-?B activation in the lung. Conclusions: CDE-induced SAP is associated with acute lung injury. The lack of increased pulmonary NF-kB activation suggests a remote source of increased lung chemokines. The liver appears to play a significant role in SAP associated lung injury and may be the source of NF- B dependent chemokines active in remote organ inflammation.

Steroid hormone synthesis by vaccinia virus suppresses the inflammatory response to infection.

The 3β-hydroxysteroid dehydrogenase (3β-HSD) isoenzymes play a key role in cellular steroid hormone synthesis. Vaccinia virus (VV) also synthesizes steroid hormones with a 3β-HSD enzyme (v3β-HSD) encoded by gene A44L. Here we examined the effects of v3β-HSD in VV disease using wild-type (vA44L), deletion (vΔA44L), and revertant (vA44L-rev) viruses in a murine intranasal model. Loss of A44L was associated with an attenuated phenotype. Early (days 1–3) after infection with vΔA44L or control viruses the only difference observed between groups was the reduced corticosterone level in lungs and plasma of vΔA44L-infected animals. Other parameters examined (body weight, signs of illness, temperature, virus titres, the pulmonary inflammatory infiltrate, and interferon [IFN]-γ levels) were indistinguishable between groups. Subsequently, vΔA44L-infected animals had reduced weight loss and signs of illness, and displayed a vigorous pulmonary inflammatory response. This was characterized by rapid recruitment of CD4+ and CD8+ lymphocytes, enhanced IFN-γ production and augmented cytotoxic T lymphocyte activity. These data suggest that steroid production by v3β-HSD contributes to virus virulence by inhibiting an effective inflammatory response to infection.

Systemic Inflammatory Response Secondary to Abdominal Compartment Syndrome: Stage for Multiple Organ Failure

The abdominal compartment syndrome (ACS) has been implicated in the pathogenesis of postinjury multiple organ failure. The ACS is defined as intra-abdominal hypertension causing adverse physiologic response. This study was designed to determine the effects of IAH on the production of interleukin-1b (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor (TNF-alpha), and the effects on remote organ injury. IAH was induced in Sprague-Dawley rats which were divided into 5 groups, 10 animals each. Intra-abdominal pressure (IAP) was increased to 20 mm Hg for 60 and 90 minutes in two different groups. In a third group following IAP of 20 mm Hg the abdomen was decompressed for 30 minutes before samples were collected. The other animals were used as controls. Hemodynamic response was monitored throughout the procedure. Cytokine levels were assessed in the plasma. Remote organ injury was assessed by histopathology and myeloperoxidase activity. IAH caused a significant decrease in MAP. After abdominal decompression MAP returned to baseline levels. A significant decrease in arterial pH was also noted. Increase in the levels of TNF-alpha and IL-6 was noted 30 minutes after abdominal decompression. Plasma concentration of IL-1b was elevated after 60 minutes of IAH. Abdominal decompression, however, did not cause a significant increase in the levels of this cytokine. Lung neutrophil accumulation was significantly elevated only after abdominal decompression. Histopathological findings showed intense pulmonary inflammatory infiltration including atelectasis and alveolar edema. IAH provokes the release of pro-inflammatory cytokines which may serve as a second insult for the induction of MOF.

Microarray profile of differentially expressed genes in a monkey model of allergic asthma.

Inhalation of Ascaris suum antigen by allergic monkeys causes an immediate bronchoconstriction and delayed allergic reaction, including a pulmonary inflammatory infiltrate. To identify genes involved in this process, the gene-expression pattern of allergic monkey lungs was profiled by microarrays. Monkeys were challenged by inhalation of A. suum antigen or given interleukin-4 (IL-4) treatment; lung tissue was collected at 4, 18 or 24 h after antigen challenge or 24 h after IL-4. Each challenged monkey lung was compared to a pool of normal, unchallenged monkey lungs. Of the approximately 40,000 cDNAs represented on the microarray, expression levels of 169 changed by more than 2.5-fold in at least one of the pairwise probe comparisons; these cDNAs encoded 149 genes, of which two thirds are known genes. The largest number of regulated genes was observed 4 h after challenge. Confirmation of differential expression in the original tissue was obtained for 95% of a set of these genes using real-time PCR. Cluster analysis revealed at least five groups of genes with unique expression patterns. One cluster contained genes for several chemokine mediators including eotaxin, PARC, MCP-1 and MCP-3. Genes involved in tissue remodeling and antioxidant responses were also identified as regulated by antigen and IL-4 or by antigen only. This study provides a large-scale profile of gene expression in the primate lung following allergen or IL-4 challenge. It shows that microarrays, with real-time PCR, are a powerful tool for identifying and validating differentially expressed genes in a disease model.

Changes in alpha(1)-adrenergic vascular reactivity in monocrotaline-treated rats.

In rats, injection of monocrotaline (MCT) causes pulmonary hypertension that leads to right ventricular failure. The aim of the present study was to characterize the responses of various vessels (the pulmonary artery, the thoracic aorta and small mesenteric arteries) to noradrenaline (NA; 10(-10)-10(-5) M) and carbachol (10 microM) in MCT-treated rats. For this purpose 6-week-old male Wistar rats ( n=13) were treated with 60 mg/kg MCT i.p. After 4-6 weeks the rats were killed and the heart, lungs and vessels removed and compared with those from age-matched saline-treated control rats ( n=47). First, the alpha(1)-adrenoceptor subtype(s) involved in the vascular NA-responses were characterized in normal rats using the alpha(1)-adrenoceptor subtype-selective antagonists 5-methylurapidil (5-MU; competitive alpha(1A)-adrenoceptor antagonist; 10(-8)-10(-6) M), BMY 7378 (competitive alpha(1D)-adrenoceptor antagonist; 10(-7)-10(-6) M) and chloroethylclonidine (CEC; irreversible alpha(1B)-adrenoceptor antagonist; 30 microM). In the pulmonary artery the pA(2) for BMY 7378 was 7.93, while that for 5-MU could not be calculated. CEC suppressed the NA-induced contraction significantly. In the thoracic aorta, the pA(2) for BMY 7378 was 8.06, while 5-MU was less effective (pA(2) 7.31). CEC again suppressed the NA-induced contraction significantly. In mesenteric arteries, CEC was ineffective whereas 5-MU induced a significant, rightwards shift of the concentration/response curve for NA (pA(2) 8.05). BMY 7378 had a lower pA(2) (6.6). MCT-treated rats developed an increased right ventricular pressure, obliteration of pulmonary vessels and inflammatory lung infiltration. In the pulmonary artery, but not in the thoracic aorta or mesenteric artery of MCT-treated rats NA-induced contraction was attenuated. In addition, carbachol-induced relaxation was reduced in the pulmonary and mesenteric arteries. In conclusion, NA-induced contraction is mediated predominantly by alpha(1A)-adrenoceptors in small mesenteric arteries, by alpha(1D)-adrenoceptors in the thoracic aorta (with a contribution from alpha(1A)- and alpha(1B)-adrenoceptors) and by alpha(1D)- and alpha(1B)-adrenoceptors in pulmonary arteries. MCT leads to reduced NA-responsiveness exclusively in the pulmonary artery that does not, however, account for the development of pulmonary hypertension, and to a more generalized endothelial dysfunction which may contribute to the pathogenesis of pulmonary hypertension in this model.

Increased replication of respiratory syncytial virus (RSV) in pulmonary infiltrates is associated with enhanced histopathological disease in bonnet monkeys (Macaca radiata) pre-immunized with a formalin-inactivated RSV vaccine.

The pathology of respiratory syncytial virus (RSV) disease in bonnet monkeys parallels findings with human RSV disease. RSV-infected animals pre-immunized with a formalin-inactivated (FI) RSV vaccine develop inflammation in peribronchiolar, perivascular, interstitial and intra-alveolar sites with lung inflammation scores significantly higher than animals with a primary RSV infection and those pre-immunized with an FI-Vero cell control vaccine (P=0.05). Animals previously infected and re-exposed to RSV had significantly lower alveolar, interstitial and total lung inflammation scores than in primary infection (P=0.05). Immunization with two intra-muscular doses of 0.5 ml of the FI-RSV vaccine administered 21 days apart resulted in little serum-neutralizing and ELISA antibody, low levels of secretory IgA and a low lymphocyte proliferative response that was significantly lower than the response observed in animals that were previously infected with live RSV. Higher RSV virus titres were detected in the lungs and lung lavage fluid of monkeys immunized with the FI-RSV vaccine than in those with a primary infection (P=0.001). RSV was detected by in situ hybridization in pulmonary inflammatory infiltrates, where the single most abundant infiltrating cellular species was macrophages, so it may be these cells that support the enhanced virus replication that contributes to the enhanced pulmonary pathology of FI-RSV immunization.

The pulmonary environment promotes Th2 cell responses after nasal-pulmonary immunization with antigen alone, but Th1 responses are induced during instances of intense immune stimulation.

The purpose of this study was to determine the nature of the CD4(+) Th cell responses induced after nasal-pulmonary immunization, especially those coinciding with previously described pulmonary inflammation associated with the use of the mucosal adjuvant, cholera toxin (CT). The major T cell population in the lungs of naive mice was CD4(+), and these cells were shown to be predominantly of Th2 type as in vitro polyclonal stimulation resulted in IL-4, but not IFN-gamma, production. After nasal immunization with influenza Ag alone, Th2 cytokine mRNA (IL-4 and IL-5) levels were increased, whereas there was no change in Th1 cytokine (IL-2 and IFN-gamma) mRNA expression. The use of the mucosal adjuvant, CT, markedly enhanced pulmonary Th2-type responses; however, there was also a Th1 component to the T cell response. Using in vitro Ag stimulation of pulmonary lymphocytes, influenza virus-specific cytokine production correlated with the mRNA cytokine results. Furthermore, there was a large increase in CD4(+) Th cell numbers in lungs after nasal immunization using CT, correlating with the pulmonary inflammatory infiltrate previously described. Coincidentally, both macrophage-inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta mRNA expression increased in the lungs after immunization with Ag plus CT, while only MIP-1beta expression increased when mice were given influenza Ag alone. Our study suggests a mechanism to foster Th1 cell recruitment into the lung, which may impact on pulmonary immune responses. Thus, while Th2 cell responses may be prevalent in modulating mucosal immunity in the lungs, Th1 cell responses contribute to pulmonary defenses during instances of intense immune stimulation.

Type I IFN modulates innate and specific antiviral immunity.

IFNs protect from virus infection by inducing an antiviral state and by modulating the immune response. Using mice deficient in multiple aspects of IFN signaling, we found that type I and type II IFN play distinct although complementing roles in the resolution of influenza viral disease. Both types of IFN influenced the profile of cytokines produced by T lymphocytes, with a significant bias toward Th2 differentiation occurring in the absence of responsiveness to either IFN. However, although a Th1 bias produced through inhibition of Th2 differentiation by IFN-gamma was not required to resolve infection, loss of type I IFN responsiveness led to exacerbated disease pathology characterized by granulocytic pulmonary inflammatory infiltrates. Responsiveness to type I IFN did not influence the generation of virus-specific cytotoxic lymphocytes or the rate of viral clearance, but induction of IL-10 and IL-15 in infected lungs through a type I IFN-dependent pathway correlated with a protective response to virus. Combined loss of both IFN pathways led to a severely polarized proinflammatory immune response and exacerbated disease. These results reveal an unexpected role for type I IFN in coordinating the host response to viral infection and controlling inflammation in the absence of a direct effect on virus replication.

Efficacy of RD3-0028 aerosol treatment against respiratory syncytial virus infection in immunosuppressed mice.

RD3-0028, a benzodithiin compound, has antiviral activity against respiratory syncytial virus (RSV) in cell culture. We used a mouse model of RSV infection to determine the in vivo effect of RD3-0028. Cyclophosphamide (CYP)-treated, immunosuppressed mice were inoculated intranasally. The lungs of the mice were removed on day 4. The virus titers of the lungs of RD3-0028-treated mice were compared to the virus titers of the lungs of virus-inoculated, untreated control mice. In an effort to increase the therapeutic effectiveness of this compound, RD3-0028 was administered by aerosol to RSV-infected mice by using a head-exposure system. Aerosols generated from reservoirs containing RD3-0028 (7 mg/ml) administered for 2 h twice daily for 3 days significantly reduced the pulmonary titer of RSV-infected mice. It is clear that the minimal effective dose of RD3-0028 for RSV-infected mice is significantly less than that of ribavirin, the only compound currently available for use against RSV disease. Furthermore, the RD3-0028 aerosol administration appeared to protect the lungs of infected, CYP-treated mice against tissue damage, as evidenced by the preservation of the lung architecture and a reduction in pulmonary inflammatory infiltrates. RD3-0028 aerosol was not toxic for mice at the therapeutic dose. The present study demonstrates the effectiveness of aerosol administration of RD3-0028 for RSV-infected mice.

Experimental study of partial liquid ventilation in the setting of acute respiratory failure induced by sea water lung lavage in rabbits.

To study the effect of partial liquid ventilation (PLV) with perfluorocarbon on acute respiratory failure, 3 groups of 17 rabbits were examined to compare. After acute respiratory failure was induced by lung lavage with sea water in 12 of the 17 rabbits, 7 of the 12 rabbits were treated with conventional mechanical ventilation (AC group) and 5 of the 12 rabbits were treated with PLV using perfluorocarbon (AP group). The remaining 5 normal rabbits without acute respiratory failure were treated with PLV with perfluorocarbon as a control group (PL group). In the PL group, PaO2, PaCO2, blood pH, pulmonary compliance or pathological findings were not so changed after PLV. In the AC and AP groups, PaCO2 significantly increased, and in contrast, PaO2 and pulmonary compliance significantly decreased after lung lavage. However, these findings improved to almost the same levels as those of a control group within 2 h after the PLV treatment in the AP group, but in the AC group, these gradually deteriorated over time. As for the pathological findings, pulmonary vascular congestion, alveolar hemorrhage and inflammatory infiltration were observed in the AC group. However, these findings were not observed in the specimens of the AP group. From these results, PLV with perfluorocarbon was shown to be useful to improve gas exchange and pulmonary functions without major side effects.

The role of CD4+ and CD8+ T cells in the protective inflammatory response to a pulmonary cryptococcal infection

Moderately virulent strains of Cryptococcus neoformans, inoculated via the trachea, cause a pulmonary infection in BALB/c mice that was gradually resolved by T lymphocyte-dependent mechanisms. The current studies, using monoclonal antibodies to deplete T cell subsets, demonstrated that CD4+ and CD8+ T cells combined to mediate a prominent pulmonary inflammatory infiltrate that included lymphocytes, macrophages, neutrophils, and eosinophils. The inflammatory response peaked 2 weeks after infection and coincided with the beginning of gradual pulmonary clearance of the infection. CD4/CD8 double deficiency (4-8-) markedly reduced the influx of all cells into the lungs. A CD4 deficiency had a more profound effect on the total number of inflammatory cells recruited to the lungs than a CD8 deficiency. Depletion of either CD8+ or CD4+ T cells significantly decreased pulmonary macrophages and neutrophils, but only a CD4 deficiency prevented the influx of eosinophils. Recruitment of CD8+ T cells occurred independently of CD4+ T cells, but CD4+ T cell recruitment to the lungs was significantly reduced in CD8-deficient mice. Mitogen-stimulated infiltrating lung lymphocytes from infected 4+8+ mice secreted both T helper cell type 1 (Th1) [interferon-gamma (IFN-gamma) and interleukin-2 (IL-2)] and Th2 (IL-4, IL-5, and IL-10) cytokines. CD4 deficiency resulted in loss of T cells secreting IL-4, IL-5, and IL-10. However, residual CD8+ T cells still secreted IL-2 and IFN-gamma. Lung T cells from CD8-deficient mice secreted similar levels of IL-4, IL-5, and IL-10 on a per lung basis compared with 4+8+ mice despite decreased numbers of CD4+ T cells, but secreted reduced levels of IFN-gamma. These experiments indicate that (1) CD4+ T cells play a dominant role in recruiting macrophages and granulocytes to the lung and (2) CD8+ T cells also mediate cellular recruitment, increase the magnitude of CD4+ T cell numbers in the infiltrate, and contribute to the local secretion of IFN-gamma. Thus, these studies demonstrate that CD8+ T cells can independently mediate an inflammatory response to a large, particulate, extracellular antigen, a role heretofore attributed almost solely to CD4+ T cells.

Perceptions of pain relief after surgery

The purpose of this study was to determine the nature of the CD4⁺ Th cell responses induced after nasal-pulmonary immunization, especially those coinciding with previously described pulmonary inflammation associated with the use of the mucosal adjuvant, cholera toxin (CT). The major T cell population in the lungs of naive mice was CD4⁺, and these cells were shown to be predominantly of Th2 type as in vitro polyclonal stimulation resulted in IL-4, but not IFN-γ, production. After nasal immunization with influenza Ag alone, Th2 cytokine mRNA (IL-4 and IL-5) levels were increased, whereas there was no change in Th1 cytokine (IL-2 and IFN-γ) mRNA expression. The use of the mucosal adjuvant, CT, markedly enhanced pulmonary Th2-type responses; however, there was also a Th1 component to the T cell response. Using in vitro Ag stimulation of pulmonary lymphocytes, influenza virus-specific cytokine production correlated with the mRNA cytokine results. Furthermore, there was a large increase in CD4⁺ Th cell numbers in lungs after nasal immunization using CT, correlating with the pulmonary inflammatory infiltrate previously described. Coincidentally, both macrophage-inflammatory protein-1α (MIP-1α) and MIP-1β mRNA expression increased in the lungs after immunization with Ag plus CT, while only MIP-1β expression increased when mice were given influenza Ag alone. Our study suggests a mechanism to foster Th1 cell recruitment into the lung, which may impact on pulmonary immune responses. Thus, while Th2 cell responses may be prevalent in modulating mucosal immunity in the lungs, Th1 cell responses contribute to pulmonary defenses during instances of intense immune stimulation.