Varying intensity of simulated infection partially affects the magnitude of the acute‐phase immune response in the subterranean rodent Ctenomys talarum

CARRIZO, MARÍA C.; ZENUTO, ROXANA R.; LUNA, FACUNDO; CUTRERA, ANA P.

Journal of Experimental Zoology Part A: Ecological and Integrative Physiology

Wiley

Año: 2023 p. 253 - 268

2471-5638

The acute phase response (APR), coordinated by a complex network of componentsof the immune and neuroendocrine systems, plays a key role in early immunedefense. This response can be elicited by a wide variety of pathogens at differentintensities (frequencies and doses), hence experimental immune challenges withantigen gradients makes it possible to evaluate sickness progression with a betterrepresentation of what occurs in natural systems. However, how infection intensitycould shape the APR magnitude in wild species is still poorly understood. Here, theimmune response was activated in the subterranean rodent Ctenomys talarum with agradient of lipopolysaccharide (LPS) doses (0.5, 1, 1.5, and 2 mg/kg of body mass).Changes in body temperature, body mass, and energetic costs were evaluated overtime. We also assessed cortisol levels, white blood cells counts and neutrophil:lymphocyte ratios, before and after injection. Results indicated that during the APR,C. talarum shows a hyperthermic response, which is maintained for 6 h, with slightdifferences among antigen doses in the pattern of thermal response and body masschange. A maximum increase in body temperature of 0.83°C to 1.63°C was observedduring the first hour, associated with a metabolic cost that ranged from 1.25 to1.41 ml O2/gh. Although no clear effects of treatment were detected on leukocyteabundance, we found increments in neutrophil: lymphocyte ratios and gradualincreases in cortisol levels corresponding to the intensity of simulated infection,which may indicate redistribution of immune cells and enhancement of immunefunction. An evident sickness syndrome was observed even at the lowest LPS dosethat was characterized by an increase in body temperature, energy expenditure, andN: L ratio, as well as a dose‐dependent increase in cortisol levels. Although in nature,other constraints and challenges could affect the magnitude and costs of immuneresponses, C. talarum mounts an effective APR with a low increase in their dailyenergy expenditure, regardless of LPS dose.