Sex differences in immune responses and immune reactivity to stress in adolescents

The immune system is the body's major defense mechanism against disease. However, psychosocial factors, such as stress, can modulate various immune responses. Although they have been examined in adult humans and other animals, sex differences in immune responses and immune reactivity to stress have rarely been examined in adolescents, particularly comparing healthy and asthmatic adolescents. In 151 healthy and asthmatic high school adolescents (91 females and 60 males), natural killer cell (NK) cytotoxicity, polymorphonuclear leukocyte (PMN) superoxide release, lymphocyte proliferative responses, and CD subsets were measured twice: once during mid-semester and again during final examinations. There was little difference in these measures between healthy and asthmatic adolescents. Similarly, only sex difference was noted in NK cytotoxicity at a 25:1 effector-to-target cell ratio, with males showing significantly higher responses than females. For PMN superoxide release, females significantly increased their responses during final examinations, whereas males demonstrated no changes. For lymphocyte proliferative responses, both females and males increased their responses during final examinations, but the magnitude of increase was much greater in males. Furthermore, racial comparisons indicated that African American adolescents (n = 16), as compared with Caucasian adolescents (n = 128), had significantly higher responses in PMN superoxide release to N-Formyl-Met-Leu-Phe (FMLP) activation during mid-semester and lymphocyte proliferative responses at both time points. Nevertheless, the overall findings indicate limited differences in immune responses and immune reactivity to stress in adolescents between males and females, healthy and asthmatic adolescents, and Caucasians and African Americans. However, further investigations with larger samples are warranted.