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Assessment of energetic costs associated to inflammatory response to phytohaemagglutinin in tuco-tucos
Jornada; XXIV Jornadas Argentinas de Mastozoología; 2011
Variability in immune defenses can arise from differential allocation of resources to immunity vs. other costly physiological processes. Relative to innate immunity, adaptive defense arms (both humoral and cell-mediated) are expected to be more expensive and slower, though they have the major advantage of generating memory of prior infections. “Slow-living species” (with low reproductive outputs, high investment per offspring, long developmental times and long adult lifespans) would rely more heavily on an adaptive immune response that, in spite of being relatively more costly and slower, would favor survival and maintenance of immune defenses over current reproduction when a trade-off is met. In Ctenomys talarum (tuco-tucos), a humoral response to a novel antigen represented an increment in the resting metabolic rate (RMR) of 20-35%, possibly leading to trade-off decisions during energetically demanding periods. Our goal in this study was to assess the energetic costs of the cell-mediated immune arm in tuco-tucos. We compared the RMR of tuco-tucos of both sexes injected with phytohemagglutinin (PHA), a vegetal lectin expected to trigger a local T-cell stimulation that results in significant swelling, to the RMR of those injected with phosphate buffered saline (PBS) during the breeding season. The magnitude of the inflammation response was significantly higher in the PHA-injected group compared to the PBS group (two-way ANOVA: df=1, F=31,78, p˂0,0001). Contrary to expected, PHA-injected animals (n=10) did not show a significant increase in their RMR in comparison to those injected with PBS (n=11, two-way ANOVA: df=1, F=3,81, p=0,06). We compare and discuss our findings regarding the energetic costs associated with the cell-mediated immune response with the results on the humoral response obtained in a previous study for the same species.