Female Scent Activated Expression of Arginase1 and Inducible NO-Synthetase in Lung of BALB/c Male Mice

SIMPLE SUMMARY: The scent of receptive females stimulates the breeding behavior of male mice. However, searching for breeding partners is associated with an increased risk of sniffing contaminated fecal and urinary marks containing various infectious agents, activating males’ immunity to protect them from infection. We found that the scent of specific pathogen-free (SPF) females stimulated male mouse immunity but was not associated with changes in the hormonal background. The percentage of T-cells decreased after the female scent treatment, affecting a specific immune reaction. The female scent caused an activation of the Nos2 and Arg1 genes in the macrophages in the lungs of male mice, which could increase resistance to potentially infectious agents. Our data showed activation of nonspecific immunity in male mice in response to the sniffing SPF female scent. We suggest that our study may impact future multidisciplinary behavioral and immunological studies and veterinary practice. ABSTRACT: Scent signals play an important role in the life of rodents. The scent of the opposite sex can modulate immunity. In mice populations with natural specific pathogens, in males, the scent of a female leads to a redistribution of leukocytes between the lung and the blood, resistance to the influenza virus, and a decrease in antibody production, but not in the development of inflammation induced by bacterial endotoxins. This study demonstrates the effect of the scent of soiled bedding of specific pathogen-free (SPF) status female mice on the percentage of different types of leukocytes in the blood, the expression of Nos2, Arg1, and Foxp3 genes, and the presence of M1/M2 macrophages in the lungs of male BALB/c mice. The scent of the female SPF mice caused a redistribution between T- and B-cells in the blood, the increase in the expression of Nos2, Arg1 genes, and the percentage of M1 type macrophages in the lung, but did not affect the different types of T-cells in the periphery or the lungs. Activation of macrophages in the lung is part of mucosal immunity, which is necessary for males as an adaptive mechanism to prevent potential infection during the search for a sexual partner.