Immunological clues to sex differences in parasitic diseases

Immune responses to parasitic infections differ between males and females as the result of distinct sex chromosomal complement and sex hormones – particularly testosterone has been shown to influence the immune response and modulate the outcome of parasitic diseases.Many tropical parasitic diseases, including Chagas’ disease, leishmaniasis, amebiasis, malaria and certain helminth infections, exhibit a bias towards the male sex, whereas a female bias exists in tapeworm infection.Selected murine models accurately mirror the male predominance in human parasitosis, including the modulation by sex hormones, and can thus be used as tools for the study of sex differences in infection. Since comprehensive knowledge of these differences is still lacking for many diseases, the availability of these models is particularly valuable. The effect of sex on the prevalence and severity of parasitic diseases is an emerging area of research. Several factors underlie sex-based differences, including sociocultural influences that affect exposure to parasites, and physiological disparities linked to biological sex. Hence, human studies must be interpreted cautiously; however, studies conducted under controlled laboratory conditions are important to validate findings in humans. Such research can more effectively elucidate the role of sex-determining physiological factors (particularly their impact on immune responses), as well as the role of sex-specific differences in resistance to, or severity of, parasitic diseases. This review focuses on the overarching impact of biological sex variables on immunity. Both human and rodent experimental data are discussed, with a focus on selected protozoan and helminth infections. The effect of sex on the prevalence and severity of parasitic diseases is an emerging area of research. Several factors underlie sex-based differences, including sociocultural influences that affect exposure to parasites, and physiological disparities linked to biological sex. Hence, human studies must be interpreted cautiously; however, studies conducted under controlled laboratory conditions are important to validate findings in humans. Such research can more effectively elucidate the role of sex-determining physiological factors (particularly their impact on immune responses), as well as the role of sex-specific differences in resistance to, or severity of, parasitic diseases. This review focuses on the overarching impact of biological sex variables on immunity.