Since scent marks of mice are harbored by parasites, their sniffing during olfactory search of the mating partner leads to increase of the infection risk. A hypothesis that sexual signals can induce, along with the reproductive behavior, non-specific immune defense against respiratory infections is tested in the present paper. It was found in the experiments on outbred ICR mice that the scent of soiled bedding from cages with mature females stimulated leukocyte intervention to the upper air-ways. Migration of the white blood cells to lung tissue was accompanied with a more prominent immune and endocrine responeses to intranasal application of the bacterial lipopolysacharide (LPS). In particular, LPS administration to male mice treated by female scent was resulted in much greater amount of leukocyte aggregations in the peribronchial areas than that was found in the males kept isolated from the female signals. The female scent also enhanced adrenocortical response to LPS administration, which was coincided with statistically significant increase of IL-1beta concentration in hypothalamus. So, chemical signals of the mature female induce travel of white blood cells to the upper air-waya in the scent treated male mice. It can increase resistance to respiratory infections, on the one hand, and aggravates stress response to inhalation of the bacterial compounds, on the other hand.