Local and systemic immune mediators of Morada Nova lambs with divergentHaemonchus contortusresistance phenotypes

Aims Local and systemic immune mediators of Morada Nova lambs with divergentHaemonchus contortusresistance phenotypes were evaluated. Methods and Results Lambs were ranked through faecal egg counts (FEC) after two parasitic challenges with 4,000H.contortusL(3). After the second challenge, the lambs underwent a third artificial infection and were euthanized 7 days later. Immune-related genes were quantified locally in abomasal mucosa and lymph nodes (CD4,IFN gamma,IL4,IL5,IL13,IL2RAandMS4A2) and systemically in the whole blood (IL4andIL13). Anti-H. contortusIgG and IgA antibodies and eosinophils and mast cells counts were also investigated. Resistant animals presented higher systemic IgG and IgA titres, both negatively correlated with FEC. Susceptible animals had higher blood levels ofIL4transcripts. At the local level, resistant lambs had higher eosinophils counts and superiorMS4A2levels in abomasal fundic mucosa, besides higher IgA levels in abomasal mucus, while susceptible lamb had superiorIL4expression in abomasal lymph nodes. Conclusion These data indicate that resistant lambs had an immune response mediated by antibody-mediated cytotoxicity. Also, the systemic humoral profile, particularly IgA isotype, seems to be a good resistance marker for Morada Nova sheep, as we found differences between groups even when FEC did not differ. (AU)