Post-mating disparity between potential and realized immune response inDrosophila melanogaster

Abstract

Reproductive costs are an essential component of evolutionary theory. For instance, an increase in reproduction is generally coupled with a decrease in immunocompetence shortly after mating. However, recent work in Drosophila melanogaster suggests that the potential to mount an immune response, as measured by the levels of immune gene expression, increases after mating. These data are in contrast to previous studies, which suggest that mating can reduce a fly's ability to survive an actual bacterial challenge (realized immunity). This pattern may be driven by some aspect of mating, independent of resource limitation, which reduces immune function by inhibiting the effective deployment of immune gene products. Though several studies have examined both the potential and the realized immunity after mating, none have examined these immune measures simultaneously. Here, we examined the link between the potential and the realized immunity in a sterile mutant of D. melanogaster. Shortly after mating, we found that female immune gene expression was high, but survival against infection was low. Surprisingly, this pattern was reversed within 24 h. Thus, estimates of immunity based on gene expression do not appear to reflect an actual ability to defend against pathogens in the hours following copulation. We discuss the possible mechanisms that may account for this pattern.

Female and male genetic contributions to post-mating immune defence in female Drosophila melanogaster

“…Other studies have measured overall defence as a function of mating in the context of experimental infection (McKean & Nunney 2001Shoemaker et al 2006;Fedorka et al 2007;Wigby et al 2008). Three of the cited studies have been performed using female D. melanogaster (McKean & Nunney 2005;Fedorka et al 2007;Wigby et al 2008), but no clear consensus has emerged even from those as to whether females suffer a meaningful reduction in immune defence after mating. Two of these studies (McKean & Nunney 2005;Wigby et al 2008) show no change owing to mating in the ability of females to clear non-pathogenic bacteria, while Fedorka et al (2007) demonstrated that females infected with a pathogenic bacterium suffer higher mortality if they have mated.…”

“…We also determined whether the change in defence is dependent on the particular combination of male and female genotypes engaging in copulation. We measured genetic variation in both sexes because we were particularly interested in assessing the potential for ongoing sexual conflict in this system, as it has been suggested in the literature that the fitness of males and females may be affected differently depending on the level of immunosuppression females experience after mating, and that this could lead to sexual conflict (Fedorka et al 2007;Lawniczak et al 2007). This hypothesis could be provisionally supported by data we have collected, which suggest that the male ejaculate plays a role in reducing female defence (S. M. Short, M. F. Wolfner & B. P. Lazzaro 2010, unpublished data).…”

The effects of temperature on host–pathogen interactions in D. melanogaster: Who benefits?

“…For the experiments, females were collect as virgins from the culture vials and then were aged for 3 days. This controlled for both age and mating status, which have both been shown to affect immune function (Fedorka et al, 2007;Fedorka and Zuk, 2005;Lawniczak and Begun, 2004;McGraw et al, 2004;Zerofsky et al, 2005).…”

Mating induces an immune response and developmental switch in theDrosophilaoviduct

“…18, or, more intriguingly, a mating-induced shift in the focus of the immune response from whole-body to the RT, as has also been suggested in ref. 19.…”