Lenina, Kyzyl, Tyva Republic, 667000 Russia, e-mail kuularg@mail.ru A b s t r a c t Humoral and cellular factors of natural resistance of animals are represented by diverse proteins, peptides, lysosomal enzymes, and immunocompetent cells contained in blood. <...> The natural resistance factors possessing antimicrobial properties additionally activate the other humoral and cellular immunity mechanisms. <...> The natural resistance system formed during the process of evolution and microevolution of domesticated animals determines their fitness to biotic and abiotic stresses caused by the action of pathogens, unfavorable natural-climatic conditions that is most importantly for animals under all-year-round pasture keeping conditions. <...> Nevertheless, the region is thought favorable for rearing native breeds of horses ( ), and highland yaks ( ), sheep ( ), goats ( ), which are well fit to such complex conditions. <...> A comparative study on natural resistance parameters in native Tuvinian horses, highland yaks, Tuvinian short-fat-tailed sheep and goats of Tuvinian population was performed by us for the first time. <...> Thus, the native Tuvinian horses are superior to goats of Tuvinian population and Tuvinian short-fat-tailed sheep in phagocytosis activity as much as 1.38 and 1.43 times, respectively (P < 0.001). <...> The maximum phagocytal index was observed in horses of native breeds (P < 0.001 and P < 0.01). <...> Highland yaks showed parameters of phagocytosis activity and phagocytal index higher than those in goats and sheep (P < 0.001). <...> The determination of the content of lysosomal-cationic proteins showed interspecific distinctions, which were most expressed in native Tuvinian horses and highland yaks. <...> Concentration of lysosomal-cationic proteins in blood serum of horses and yaks was characterized by the maximum values, while this index in goats and sheep was lower (P < 0.001). <...> Positive correlation ( = 0.86-0.98) between phagocytosis activity, phagocytal index and the level of lysosomal-cationic proteins was found to be in the all animals studied. <...> We also revealed interspecific diversity in the content of immunoglobulins of primary isotypes (IgG, IgM, IgA), the high values of which were observed in goats and sheep. <...> Keywords: natural resistance, local Tuva horses, high-mountain yak, Tuva goat population, Tuva short-fat-tailed sheep. <...> Humoral and cellular factors of natural resistance of animals are <...>