Association of Ovar-DRB1 alleles with innate immune responses in sheep.

Background: Major histocompatibility complex (MHC) is the best characterised genetic region associated with adaptive immune responses, including humoral and cell-mediated immunities.

Objectives: In this study, the association of MHC class II alleles with inflammatory cytokines and acute-phase proteins was evaluated in sheep population.

Methods: Allelic diversity of second exon of ovine DRB1 locus (Ovar-DRB1.2) was determined in 100 indigenous Iranian Lori-Bakhtiari fat-tailed sheep using restriction fragment length polymorphism and direct sequencing methods. The association of DRB1.2 alleles with inflammatory cytokines (interleukin-1β, IL-1β; IL-6 and tumour necrosis factor-α) and acute-phase proteins (serum amyloid A, alpha-1-acid glycoprotein and haptoglobin) was examined using generalised linear model and multivariate regression analysis.

Results: Seven distinct RsaI restriction patterns and fourteen alleles were identified in this population. Allele DRB1*2101 showed a negative influence on the IL-6 response and was associated with lower serum level of IL-6. DRB1.2 heterozygous individuals also showed higher haptoglobin concentration than homozygotes.

Conclusions: These results provide additional support for the association between Ovar-DRB1 alleles and regulation of immune responses in sheep population. Description of MHC polymorphism and its role in the controlling of immune responses will increase our understanding of host-pathogen interactions, and ultimately facilitate the selection of disease-resistant flocks in genetic breeding programs.