ABSTRACT
Before the advent of antibiotics there was an increase in prevalence of infectious disease (morbidity) and mortality in male children compared with females and while the mortality has decreased, morbidity is still greater in male children. In recent years a better understanding of the effect of gender on the immune system has thrown some light on the basis of these findings. The effects are seen at the level of the genes inherited on sex chromosomes, the different reproductive anatomy of females versus males, and the influence of sex hormones on immunity. At the genetic level, several of the genes important for immune responses (e.g., CD40L) have been localized on the X chromosome and several X-linked primary immunodeficiency diseases have been described that primarily affect males (Section J2). However, in addition to the role of the X chromosome, females generally have a higher absolute number of CD4+ T cells in their circulation and show a more robust cell- and antibody-mediated response to many infections compared with males. For example, there is a tendency for levels of serum IgG and IgM antibodies to 298be higher throughout life in females compared with males. Furthermore, increased specific primary and secondary responses to microbial infections such as Escherichia coli, Brucella, measles, rubella, and hepatitis B have been reported in females. This could contribute to the decreased susceptibility to infection and general trend in heightened immune response to microbial infections compared with males (Table 1).
