Metcalf, C.J.E. & Graham, A.L. Nat.Commun. 9, 4391 (2018)

There are trade-offs to the responsiveness of one’s immune system. Detect and react quickly to nip illness in the bud, but risk overreactions and autoimmune complications to benign situations. Save the bug-fighting energy until it’s really needed, but risk the establishment of a pathogen that the body could’ve fought off earlier. Females of various species, including humans, tend towards the former strategy; males, the latter. A new mathematical framework from researchers at Princeton attempts to explain the immune discrepancies between the sexes.

Authors Metcalf and Graham define variables that drive sensitivity to pathogens versus the magnitude of immune response, and then evaluate those against life history. Reproduction seems to be a big driver—because females are more limited in their reproductive capacity than males, infections pose a greater risk to their reproductive success, thus pushing the offspring-bearing sex towards more precautionary sensitivity.