Immunization of Male BALB/c and C57BL/6 Mice Alters the Composition of Their Urine and the Response of Females to Its Odor

Odors play a key role in animal communication and mate choice. Male urinary odor becomes less attractive to mature females when males get infected or have their immune system activated. The development of the immune response at early stages is related to the production of both pro- and anti-inflammatory cytokines. To explore the chemical basis of the observed differences and analyze the effects of female interactions with the urinary odor of antigen-stimulated males, the males of inbred BALB/c (Th1) and C57BL/6 (Th2) mice were immunized with keyhole limpet hemocyanin (KLH). The odor of male urine collected 3 days after immunization proved to be less attractive to females of both strains compared to the odor of control males. Herewith, BALB/c females sniffed the urine of immunized males less frequently, while C57BL/6 females demonstrated a shorter duration of grooming in olfactory tests with urine of immunized males. The altered response of females to the odor of male urine collected on day 3 after KLH immunization matched antigen-induced modulation of relative levels of volatile organic compounds detected in urine samples by gas chromatography/mass spectroscopy (GC-MS). Males of both strains, after KLH immunization, exhibited an increase in the content of nonanal, benzothiazole, 2-sec-butyl-4,5-dihydrothiazole, and [1,4,5]-oxadithiepane. At the same time, no compounds were found, whose content changed multidirectionally in the urine of males after immunization in a strain-dependent manner.