Women have a higher proportion of key immune cells between puberty and menopause, which may be linked to the sex hormone oestrogen and explain why they are less susceptible to certain infectious diseases than men, according to a new study led by researchers at UCL. The study, published in the Journal of Experimental Medicine , is one of the first to explore how sex chromosomes and sex hormones combine to influence the immune systems of healthy individuals across a wide range of ages and gender