MHC-I provides both quantitative resistance and susceptibility to blood parasites in blue tits in the wild
Major histocompatibility complex (MHC) genes are central for the adaptive immune response against parasites. Here, we investigated potential associations among MHC-I alleles and blood parasite infections in a natural breeding population of a passerine bird, the blue tit Cyanistes caeruleus, in central Spain. We screened both infection status (presence/absence of infection) and infection intensity