Increased natural killer-cell mobilization and cytotoxicity during marital conflict

Natural killer (NK) cells are reproducibly mobilized into the circulation in response to intense physical exercise or acute psychological stress, and altered expression of adhesion molecules potentially contributes to NK-cell mobilization. Studies of leukocyte mobilization during acute stress have used psychological stressors which facilitate tight experimental control but have limited applicability to everyday life. We therefore used a laboratory model of marital conflict as an experientially meaningful acute stressor to elucidate relationships among conflict, cardiovascular reactivity, and altered leukocyte phenotype and function. Forty-one ethnically diverse, nondistressed, healthy married couples were asked to discuss a specific problem in their marriage for 15 min. Blood pressure and heart rate were measured before, during, and after the discussion, and blood was remotely drawn at the same time points to quantify numbers of specific leukocyte subsets, NK-cell adhesion molecule expression, and NK cytotoxicity. Couples responded to the conflict task with cardiovascular reactivity; increases in the percentages of circulating NK cells and CD8(+) T cells and decreases in the percentage of circulating CD4(+) T cells; decreases in the percentage of NK cells that express L-selectin; and increases in NK-cell cytotoxicity without a commensurate increase in per-cell cytotoxicity. Rapid downregulation or shedding of L-selectin (CD62L) from NK cells did not contribute to their mobilization during conflict. Instead, CD62L(-) NK cells were mobilized while CD62L(+) NK cells were selectively retained in the vascular marginating pool and/or in extravascular tissue. From a broader perspective, the data support the hypothesis that altered trafficking of specific leukocyte subsets is an integral component of the fight-or-flight response to an acute stressor.