Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes

Aims Local and systemic immune mediators of Morada Nova lambs with divergent Haemonchus contortus resistance phenotypes were evaluated. Methods and Results Lambs were ranked through faecal egg counts (FEC) after two parasitic challenges with 4,000 H.contortus L3. 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, IFNγ, IL4, IL5, IL13, IL2RA and MS4A2) and systemically in the whole blood (IL4 and IL13). Anti‐H. contortus IgG 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 of IL4 transcripts. At the local level, resistant lambs had higher eosinophils counts and superior MS4A2 levels in abomasal fundic mucosa, besides higher IgA levels in abomasal mucus, while susceptible lamb had superior IL4 expression 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.