RESUMO
Granulocyte macrophage-colony stimulating factor (GM-CSF) is a cytokine with the capacity to promote inflammation in a wide variety of infectious and inflammatory diseases. These conditions include allergic airway inflammation, which is driven by T-helper 2 (Th2) cells. Because of the importance of Th2 cells in parasite infections, we have investigated the role of GM-CSF in mice infected with the nematode Nippostrongylus brasiliensis. The effect of primary and secondary infection was investigated in mice lacking functional genes for GM-CSF (CSF2 genes) (ΔGM-CSF mice), and in mice lacking the cytokine receptor common ß chain (Δß mice), the latter being unable to signal in response to GM-CSF and interleukin (IL)-5. ΔGM-CSF mice showed no significant defect in parasite immunity, measured by larval numbers in the lungs, worm numbers in the intestine or egg numbers in the faeces, in either primary or secondary infection. By contrast, the Δß mice showed increased parasite burden, with higher numbers of lung larvae after secondary infection and higher numbers of intestinal worms and faecal eggs after both primary and secondary infection. Unexpectedly, there were increased numbers of circulating eosinophils in the ΔGM-CSF mice, associated with significantly reduced larval numbers in the lungs. These results indicate that GM-CSF is redundant in protection against N. brasiliensis infection, and that the increased susceptibility of Δß mice to infection is likely to be attributed to the lack of IL-5 signalling in these mice. The results suggest that clinical use of agents that neutralise GM-CSF may not be associated with increased risk of parasite infection.
Assuntos
Subunidade beta Comum dos Receptores de Citocinas/metabolismo , Eosinófilos/imunologia , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Nippostrongylus/imunologia , Infecções por Strongylida/imunologia , Infecções por Strongylida/prevenção & controle , Animais , Subunidade beta Comum dos Receptores de Citocinas/genética , Subunidade beta Comum dos Receptores de Citocinas/imunologia , Fator Estimulador de Colônias de Granulócitos e Macrófagos/genética , Fator Estimulador de Colônias de Granulócitos e Macrófagos/imunologia , Imunoglobulina E/sangue , Intestinos/imunologia , Intestinos/parasitologia , Larva , Pulmão/imunologia , Pulmão/parasitologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Carga Parasitária , Células Th2/imunologiaRESUMO
Complement may be important for immunity to infection with parasitic helminths, by promoting the recruitment of leukocytes to infected tissues and by modulating the function of cytotoxic effector leukocytes. However, the importance of complement in vivo during helminth infection is poorly understood. In this study, mice lacking classical (C1q-deficient), alternative (factor B-deficient) or all pathways of complement activation (C3-deficient) were used to assess the role of complement in immunity to the nematode Nippostrongylus brasiliensis. Double-mutant complement-deficient/IL-5 transgenic (Tg) mice were used to determine if complement is required for the strong eosinophil-dependent resistance to this parasite. Complement activation on larvae (C3 deposition), extracellular eosinophil peroxidase activity, larval aggregation and eosinophil recruitment to the skin 30 min post-injection (p.i.) of larvae were reduced in factor B-deficient mice. Inhibition of the C5a receptor with the antagonist PMX53 impaired eosinophil and neutrophil recruitment to the skin. C3 deposition on larvae was minimal by 150 min p.i. and at this time cell adherence, larval aggregation, eosinophil recruitment and degranulation were complement-independent. Factor B and C3 deficiency were associated with higher lung larval burdens in primary infections. Complement-deficient/IL-5 Tg mice were highly resistant to N. brasiliensis, suggesting that eosinophils can limit infection in a complement-independent manner. Potent secondary immunity was similarly complement-independent. In conclusion, although the alternative pathway is important for parasite recognition and leukocyte recruitment early in N. brasiliensis infections, the parasite soon becomes resistant to complement and other factors can compensate to promote eosinophil-dependent immunity.
Assuntos
Proteínas do Sistema Complemento/imunologia , Eosinófilos/imunologia , Imunidade Celular/imunologia , Imunidade Inata/imunologia , Nippostrongylus/imunologia , Animais , Basófilos/citologia , Basófilos/imunologia , Basófilos/parasitologia , Adesão Celular , Degranulação Celular/imunologia , Movimento Celular , Complemento C3/imunologia , Eosinófilos/citologia , Eosinófilos/parasitologia , Eosinófilos/fisiologia , Feminino , Fertilidade , Intestinos/imunologia , Intestinos/parasitologia , Larva/citologia , Pulmão/imunologia , Pulmão/parasitologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Infiltração de Neutrófilos/imunologia , Nippostrongylus/citologia , Pele/imunologia , Pele/parasitologia , Infecções por Strongylida/imunologiaRESUMO
Eosinophils are an important feature of immune responses to infections with many of the tissue-invasive helminth parasites. The cytokine IL-5 and a high-affinity double GATA-binding site within the GATA-1 promoter are critical for eosinophilopoiesis. In this study, we believe we demonstrate for the first time that defects in eosinophilopoiesis are associated with impaired resistance to Nippostrongylus brasiliensis. Primary and secondary infections were established in wildtype (WT), IL-5(-/-) and DeltadblGATA mice. Resistance to secondary infections was impaired in IL-5(-/-) and DeltadblGATA mice, with significantly more larvae able to reach the lungs 2 days p.i. Pulmonary inflammation was minimal in all strains in the first 2 days of both primary and secondary infections, suggesting that eosinophil-dependent resistance occurred before larvae reached this site. Intestinal worm burdens and/or parasite egg production in primary infections were greater in animals with defective eosinophilopoiesis. While larvae did reach the gut by day 3 of secondary infections of WT and IL-5(-/-) mice, worms were expelled by day 7, even in the complete absence of eosinophils in tissues of the small intestine. This and our previous studies indicate that N. brasiliensis are likely to be exquisitely sensitive to attack by eosinophils soon after entry into the skin. Eosinophils in the gut may make a modest contribution to resistance on first exposure to the parasite, but are not required for expulsion in either primary or secondary infections. In order to mount an effective immune response it may be vital for the host to identify and attack the parasite before it implements immune evasion strategies and migrates to other anatomical sites. These observations may be of particular significance for the development of successful vaccines against hookworms and other nematodes.
Assuntos
Eosinófilos/imunologia , Interleucina-5/imunologia , Enteropatias Parasitárias/imunologia , Nippostrongylus/imunologia , Infecções por Strongylida/imunologia , Animais , Eosinófilos/parasitologia , Feminino , Interleucina-5/genética , Enteropatias Parasitárias/genética , Pulmão/imunologia , Pulmão/parasitologia , Masculino , Camundongos , Camundongos Endogâmicos CBA , Nippostrongylus/genética , Contagem de Ovos de Parasitas , Pele/imunologia , Pele/parasitologia , Estatística como Assunto , Infecções por Strongylida/genética , Infecções por Strongylida/parasitologiaRESUMO
Complement activation and C3 deposition on the surface of parasitic helminths may be important for recruitment of leukocytes and for damage to the target organism via cell-mediated mechanisms. Inhibition of complement activation would therefore be advantageous to parasites, minimizing damage and enhancing migration through tissues. The aim of this study was to determine ex vivo if complement activation by, and leukocyte adherence to, the nematode Nippostrongylus brasiliensis change as the parasite matures and migrates through the murine host. Pathways of activation of complement and the mechanism of adherence of leukocytes were also defined using sera from mice genetically deficient in either C1q, factor B, C1q and factor B, C3, or C4. Substantive deposition of C3 and adherence of eosinophil-rich leukocytes were seen with infective-stage (L3) but not with lung-stage (L4) larvae. Adult intestinal worms had low to intermediate levels of both C3 and leukocyte binding. For L3 and adult worms, complement deposition was principally dependent on the alternative pathway. For lung-stage larvae, the small amount of C3 detected was dependent to similar degrees on both the lectin and alternative pathways. The classical pathway was not involved for any of the life stages of the parasite. These results suggest that in primary infections, the infective stage of N. brasiliensis is vulnerable to complement-dependent attack by leukocytes. However, within the first 24 h of infection, N. brasiliensis acquires the ability to largely avoid complement-dependent immune responses.