On sex differences in optimal immunity.

Sex biases in immunity have generated much interest because of their possible connection with sex differences in reproductive strategies. Researchers have often argued that males should invest less in immunity than should females. In a recent paper, Stoehr and Kokko challenge this reasonably substantiated view of 'susceptible males'. Their model, and another by Medley, helps highlight relevant tests that could explain other important sources of within-species variation in immunity and its importance to parasitism.