[Deacon]

another Nandi post;

Hormonal influences. T helper 1 (TH1) cells secrete proinflammatory cytokines and promote cell-mediated immune responses, whereas TH2 cells trigger antibody production. In multiple sclerosis (MS) and rheumatoid arthritis (RA), there are features characteristic of a TH1 immune response directed against autoantigens in the central nervous system and joints, respectively. Pregnancy and systemic lupus erythematosus (SLE) favor a TH2 environment. Sex hormones (such as progesterone) that promote the development of a TH2 response antagonize the emergence of TH1 cells. This may explain why in multiple sclerosis and rheumatoid arthritis disease symptoms improve during pregnancy, whereas in lupus, they do not.