Interactions between innate immunity, steroid hormones, and body condition in female fence lizards (Sceloporus undulatus)

Abstract

This study tests for potential interactions between innate immunity, the steroid hormones corticosterone (CORT) and progesterone, and body condition in female Eastern fence lizards (Sceloporus undulatus). Seasonal changes were investigated during the active season and we tested for an affect of one-hour confinement on innate immunity. Innate immunity was measured by an individual's plasma bacterial killing capacity, total circulating leukocyte counts, and differential circulating leukocyte percentages. Baseline circulating blood or plasma CORT concentrations positively correlated with percent monocytes but not the other immune measures. CORT increased with confinement but failed to elicit a change in immune function. We observed a seasonal change in percent lymphocytes, which peaked in the spring, percent heterophils, which peaked in the summer, and ectoparasitic mites, which peaked in late spring. Overall, our predictions that baseline steroid hormones would be immune suppressing and that one-hour confinement would be immune enhancing were not strongly supported.