A person’s biological sex, gender role and sex hormones all influence susceptibility to contracting infections, the immune responses to these, the clinical features of the disease, the response to treatment and even to vaccination. The differences in these three factors make the immune system response stronger and more effective in women than in men. This means infections in women are usually milder, but also that women are more prone to developing autoimmune or inflammatory diseases, such as lupus or rheumatoid arthritis.
The immune system protects against infections and external agents which are theoretically harmful to the body. Although the immune systems of women and men are similar, women develop a much stronger immune response than men. Both the initial response to the pathogen (innate immunity) and the subsequent formation of antibodies to it (adaptive immunity) are stronger and more effective in women than in men. This means women are much less susceptible to infection while their body fights it more effectively. Also, in general, women have a greater response to vaccination. An example of this is the greater severity and mortality in men, especially those under 60 years of age, towards SARS-CoV-2 infection, seen in countries where both men and women had equal access to the health system.
Conversely, this intense response means women are more prone to developing autoimmune or inflammatory diseases, such as lupus or rheumatoid arthritis. In fact, 80% of autoimmune diseases occur in women. In autoimmune and inflammatory diseases, the immune system gets out of control and begins to "attack" the body itself, causing damage and inflammation.
Among the factors that play an important role in this different immune response is biological sex. Understood as the sex assigned at birth, biological sex causes the expression of chromosomes or genetic material to be different in women and men. These genetic differences lead to a different formation of components in the immune system. For example, the number of different types of immune cells is different between women and men. This difference in the number of immune system cell types means the immune response between sexes is different.
Another important factor is the expression of sexual hormones between both sexes. Sex hormones have been observed to have an effect on the modulation of the immune system. For example, testosterone has an immunosuppressive effect; that is, it reduces the proliferation of specific immune system cells. This means that men are more sensitive to certain infections as they have more marked testosterone peaks.
Finally, gender, defined as the role established by the social and cultural context, increases or decreases exposure to certain pathogens and the access to healthcare, which is determinant in the evolution and prognosis of certain pathologies.
Occupational and recreational activities related to sex can affect the exposure of pathogens. For example, as women tend to assume caregiving functions, they tend to be more exposed to childhood infections; while men, dominating in certain professions, tend to have an increased risk of developing certain diseases, such as silicosis in mining. In addition, the role of gender has also affected the development of disease throughout history, due to the impact on therapeutic decisions. For example, prioritising visiting a doctor and having better access to the health system.
Despite increasing knowledge about the differences in immune system functioning between men and women, there are few studies that analyse data referring to the development of diseases by sex. These differences should continue to be studied in order to provide adequate individual treatment for each person.