Differences in immune parameters are associated with resistance to Haemonchus contortus in Caribbean hair sheep

P>Caribbean hair sheep are more resistant to gastrointestinal nematodes than conventional wool breeds, but mechanisms that confer resistance are not fully understood. This study compared immune effector cell populations and antibody concentrations in 12 hair and 12 wool lambs infected with the abomasal parasite Haemonchus contortus and sacrificed at 3 or 27 days post-infection (p.i.) and 14 uninfected animals of each breed. Faecal egg counts were over 2 center dot 5-fold higher (P = 0 center dot 12) and packed cell volumes approximately 8% lower (P < 0 center dot 10) in infected wool lambs. Abomasal lymph nodes were heavier in infected animals (P < 0 center dot 05) and infected hair sheep had larger lymph nodes than infected wool sheep (P < 0 center dot 05). Tissue eosinophil concentrations were likewise larger (P = 0 center dot 07) in hair compared with wool sheep at 3 days p.i. Circulating levels of IgE and IgA in uninfected lambs were higher in hair sheep (P < 0 center dot 05) and during infection, hair sheep had higher serum IgA than wool sheep at 3, 5, and 21 days p.i. (P < 0 center dot 05). Serum IgE in infected lambs did not differ between breeds, but concentrations of IgE in lymph nodes were higher (P < 0 center dot 01) at 27 days p.i. in infected hair sheep.