IL-1β-independent activation of lung immunity in male mice by female odor

In previous studies, we showed that long-term perception of female odor increases flu virus resistance in male mice. To expand on this finding, we examined the ability of female chemical cues to rapidly induce leukocyte mobilization into male lung tissue as a critical condition of signal-derived respiratory infection risk reduction, which is usually associated with sniffing scent marks. Here, we compared the immune and endocrine effects of female chemical cues and lipopolysaccharide (LPS) as common triggers of innate immunity. The number of leukocytes in the lung tissue, concentrations of IL-1β in lung and hypothalamus, and plasma corticosterone and testosterone levels were assessed in ICR male mice 2h after the intranasal application of female urine, LPS or urine and LPS. Both stimuli induced leukocyte mobilization but, in contrast to LPS, female urine alone did not stimulate increased IL-1β levels in lung and hypothalamus. Plasma corticosterone increased and plasma testosterone decreased in response to LPS, whereas the concentrations of these hormones did not change in response to female chemical cues. Thus, the present study gives additional evidence for an anticipatory adaptation of male mice to potential breeding risks. Appreciable mobilization of leukocytes to the lungs requires less than 2h and develops through an IL-1β-independent pathway.