Vertebrates exhibit sexual dimorphism in response to infectious diseases and in morbidity and mortality rates to various pathogens. Females are generally more immunocompetent than males, despite their increased reproductive burden and the immunosuppressive effects of gestation. In addition, females generally have lower incidences of cancer compared to males; however, they have higher rates of autoimmune disorders. These sex differences may be a result of life history differences, sexual selection, genetics, and/or the physiological effects of hormones. As highly social mammals with complex life histories, primates offer a unique opportunity to investigate the evolution of enhanced female immunocompetence. This review aims to examine the evidence of this immunity gap, understand current hypotheses for its evolution, and explore the potential role of X chromosome specific genes and heterozygosity within this framework.
Keywords: X chromosome; evolution; genetics; immune system; life history; selection; sexual dimorphism.
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