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 whenmales get infected or have their immune system activated. The developmentof the immune response at early stages is related to the productionof both pro- and anti-inflammatory cytokines. To explore the chemicalbasis of the observed differences and analyze the effects of femaleinteractions with the urinary odor of antigen-stimulated males,the males of inbred BALB/c (Th1) and C57BL/6 (Th2) mice were immunizedwith keyhole limpet hemocyanin (KLH). The odor of male urine collected3 days after immunization proved to be less attractive to femalesof 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 groomingin olfactory tests with urine of immunized males. The altered responseof females to the odor of male urine collected on day 3 after KLHimmunization matched antigen-induced modulation of relative levelsof volatile organic compounds detected in urine samples by gas chromatography/massspectroscopy (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 afterimmunization in a strain-dependent manner.