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Sex differences in immune responses: Hormonal effects, antagonistic selection, and evolutionary consequences
Jacob Roved1, Helena Westerdahl1, Dennis Hasselquist1
1Department of Biology, Lund University, Ecology Building, 223 62 Lund, Sweden.
Hormones and Behavior
|December 14, 2016
Summary
Sex hormones influence immune responses, with females showing stronger differences in type 2 immunity than type 1. This suggests sexually antagonistic selection may impact immune genes, particularly those linked to type 2 responses.
Area of Science:
- Immunology
- Endocrinology
- Evolutionary Biology
Background:
- Sex differences in parasite load and immune responses are observed across vertebrates.
- Sex hormones like testosterone (immunosuppressive) and estrogen (immunoenhancing) modulate immune activity.
- T-helper cells (Th1 for cell-mediated, Th2 for humoral immunity) play key roles in adaptive immunity.
Purpose of the Study:
- To review literature on sex hormone effects on Th1/Th2 immune responses.
- To hypothesize how these effects contribute to sex differences in immunity.
- To propose a novel hypothesis on sexually antagonistic selection acting on immune genes.
Main Methods:
- Literature review of studies on sex hormones and immune responses.
- Analysis of sex hormone effects on Th1 and Th2 immune pathways.
- Synthesis of findings to propose evolutionary hypotheses.
Main Results:
- Estrogen and progesterone enhance type 2 and suppress type 1 responses in females.
- Testosterone suppresses type 2 responses and has variable effects on type 1 in males.
- Sex differences in immunity are predicted to be stronger for type 2 than type 1 responses.
Conclusions:
- Hormone-mediated sex differences in immunity may drive genetic conflicts.
- Sexually antagonistic selection is hypothesized to be stronger on type 2-associated immune genes than type 1-associated genes.
- Ecological and behavioral factors (mating systems, parasite load) influence these sex differences.
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