“…Amino acid changes near or within the functional domains of immune system proteins are one of the main molecular mechanisms underlying adaptations to environmental pathogens [4,120]. Mutations giving rise to habitat-specific functional adaptive variation in immune system genes (IGHM, IGHE IGH, CD14, CD40, CD80, IFNAR2, LY96, TAB 1, TICAM1, TLR4, MDA5, chicken type lysozyme, and pIGR) have been observed in different vertebrates and can happen through insertions (e.g., MUC7 in primates) or gene duplications [121][122][123][124][125][126][127][128]. For the pIGR specifically, research suggests that the observed mutations occurred through an insertion of transposable elements [127].…”