The article discusses the significant sex-based differences in immune responses, which are crucial for understanding and managing diseases. These differences are influenced by X-linked genes, hormones, and societal contexts. Despite these differences, health research and clinical practice often overlook them, leading to suboptimal disease management for both sexes. The article highlights that males generally have higher rates of infection and severity compared to females, while females are more susceptible to sexually transmitted infections and certain autoimmune diseases. The X chromosome plays a key role in these differences, with X-inactivation providing dosage compensation and influencing disease susceptibility. Estrogens also significantly impact immune responses, affecting cell-mediated and humoral immunity, and influencing the menstrual cycle. The article emphasizes the need for sex-based differences to be considered in drug development and clinical trials to ensure effective and safe treatments for both sexes.The article discusses the significant sex-based differences in immune responses, which are crucial for understanding and managing diseases. These differences are influenced by X-linked genes, hormones, and societal contexts. Despite these differences, health research and clinical practice often overlook them, leading to suboptimal disease management for both sexes. The article highlights that males generally have higher rates of infection and severity compared to females, while females are more susceptible to sexually transmitted infections and certain autoimmune diseases. The X chromosome plays a key role in these differences, with X-inactivation providing dosage compensation and influencing disease susceptibility. Estrogens also significantly impact immune responses, affecting cell-mediated and humoral immunity, and influencing the menstrual cycle. The article emphasizes the need for sex-based differences to be considered in drug development and clinical trials to ensure effective and safe treatments for both sexes.