Meeting Abstract
Infectious pathogens are ubiquitous in natural environments, and coping with them involves physiological, immunological, and behavioral responses. Expression of immune responses may vary with age, within the context of immune system development and immunosenescence. Immature and elderly individuals often experience more severe illness in response to infection than those in young adulthood. Ontogenetic differences in immune response may result in differential contribution of age classes to disease transmission. Whether these host responses are aimed at preventing infection (resistance) and/or mediating damage caused by pathogens (tolerance) may also play a significant role in mediating disease dynamics. Cytokines are important agents in both host resistance and tolerance, but anti-inflammatory cytokines in particular have been identified as mediators of host tolerance, mitigating damage due to inflammation. Here, we investigated the balance of pro-inflammatory and anti-inflammatory cytokine responses, representative of tolerance, of three age groups of Zebra finches. Pro-inflammatory cytokines IFN-γ and IL-6 and anti-inflammatory cytokines TGF-β and IL-10 were tested. We hypothesized that tolerance would be reduced in very young and very old individuals. Specifically, we predicted that fledged and old-aged finches would have a higher level of pro-inflammatory cytokines relative to anti-inflammatory cytokines. We further predicted that recently matured individuals would have a relatively higher level of anti-inflammatory cytokines, and therefore higher tolerance. Because pathogen load is typically unaffected by tolerance, recently matured individuals may be highly competent and experience increased transmission efficiency. Ultimately, this study aimed to elucidate the age-dependent role of cytokine expression in mediating disease dynamics in natural ecosystems.
