The acute phase response in bats (Carollia perspicillata) varied with the time and dose of the immune-challenge

The acute phase response (APR) is a core component of the innate immune response and represents the first line of immune defense used in response to infections. Although several studies with vertebrates reported fever, decrease in food intake and body mass, as well as increase in neutrophil/lymphocyte ratio and total white blood cell count after lipopolysaccharide (LPS) inoculation there was great variability in the magnitude of these responses. Some of these differences might reflect, to some extent, differences in time of endotoxin inoculation (during activity or resting periods) and dose; however, no study in the literature has evaluated the synergistic effect of these two factors in vertebrates. Therefore, our study tested the interplay between LPS dose and time of injection on selected physiological (fever and increase in total white blood cell count and neutrophil/lymphocyte ratio), and behavioral (food intake) components of APR using a Neotropical fruit-eating bat (Carollia perspicillata) as a model organism. We predicted that LPS would trigger a dose- and time-dependent response on APR components. APR components were assessed in resting and activity periods after injection of three doses of LPS (5, 10 and 15 mg/kg LPS). The results showed that LPS-evoked changes in skin temperature, food intake, neutrophil lymphocyte ratio depend markedly on the LPS dose and/or time that LPS is administered.