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The Authors investigated polymorphism of the bovine BoLA‑DRB3 gene in connection with resistance or susceptibility to brucellosis of two Kazakh meat breeds, Auliekol and Kazakh Whiteheaded breeds, using PCR‑RFLP. In Auliekol cattle (n = 158), 22 alleles were detected in the brucellosis group, and 24 alleles were shown in the healthy group. BoLA-DRB3 alleles *3, *4, *19, *21 were more common in healthy animals, while Brucella‑positive cattle were more frequently carriers of alleles *7, *10, *18. In Kazakh Whiteheaded cattle (n = 146), 21 alleles were detected in infected and 23 alleles in healthy cattle. Alleles *3, *8, *21 significantly predominate in healthy cattle, while alleles *7, *11, *16 are typical for animals with brucellosis. This study identified BoLA-DRB3 alleles associated with genetic resistance (*3 and *21) and susceptibility (*7) to brucellosis; remarkably, resistance alleles are shared by two important meat breeds of Kazakhstan.

Expression analysis of immune response genes in the mammary gland tissues of both healthy and infected animals help to explain the genetic basis of differential immune response. This study was conducted to analyze the differential expression of MHC class II DRB3 gene, in mastitis-affected and healthy animals of indicus (Sahiwal) and crossbred (Karan Fries) cattle. Real-time PCR was performed on the cDNA synthesized from the RNA isolated from PBMCs of the mastitis and healthy animals. However, no significant difference was observed in the expression of DRB3 in the two populations. The results point towards polymorphism supposed to be playing major role in differential immune response, rather than the expression of DRB3 gene as far as state of udder health is concerned.