Peripheral immune cell composition may be partially regulated by circulating hormone levels given the expression of estrogen, progesterone, and androgen receptors found on many immune cells and the sexually dimorphic responses to immune challenges (including brain injury).24–27 Whereas sampling sex hormone levels on all study participants would be ideal, a feasible alternative for females could be to implement self-reported menstrual cycle surveys to investigate associations between menstrual regularity and timing and the inflammatory variables in question. The gene discussed is AR; the disease is brain injury.