It is suggested that pathogen and parasite avoidance act as a driving force for kin selection. Preferential association with relatives decreases the probability of infection with unfamiliar pathogens. Altruistic behavior towards kin will further decrease the danger of infection by increasing the representation of relatives in a group. Such a behavioral strategy could evolve if pathogen resistance were heritable. Highly polymorphic major histocompatibility (MHC) genes largely determine heritable resistance to particular pathogens.
Steroidal estrogens can regulate inflammatory immune responses and may be involved in the suppression of multiple sclerosis (MS) during pregnancy. However, the risks and side effects associated with steroidal estrogens may limit their usefulness for long-term MS therapy. Selective estrogen receptor modulators (SERMs) could provide an alternative therapeutic strategy, because they behave as estrogen agonists in some tissues, but are either inert or behave like estrogen antagonists in other tissues.