Oestrogens affect both innate and adaptive immune function. Oestradiol can have bipotential effects with low doses enhancing and high doses reducing proinflammatory cytokine production [126] . Low E2 concentrations promote helper T cell type 1 (Th1) responses and cell-mediated immunity and high concentrations of E2 augment helper T cell type 2 (Th2) responses and humoral immunity which may be responsible for some female as well as pregnancy-associated changes in immune responses [126] .