Plasma beta-endorphin levels and natural-killer cells in two cases of congenital indifference to pain.

We have investigated plasma beta-endorphin (beta-E), ACTH, and cortisol in two cases of congenital indifference to pain (CIP), a rare syndrome characterized by unresponsiveness to painful stimuli. As the two patients had frequent skin infections, we also studied lymphocyte response to mitogens in the absence or presence of beta-E. In addition, we explored a series of lymphocyte membrane antigens related to different aspects of the immune response, such as CD3+, CD4+, CD8+, B, NK Leu 7, Leu 9, and Leu 19, anti-interleukin-2 receptor (anti-TAC). Plasma beta-E levels in the two patients were significantly higher than in controls, whereas plasma ACTH and cortisol levels were normal. Lymphocyte response to the mitogen phytohemagglutinin was normal. The expression of Leu 7, Leu 9, and Leu 19, three antigens related to natural killer cells, was decreased by about 50%. The results indicate that in the two cases of CIP studied, high plasma beta-E levels are associated with a reduction in the expression of natural killer cells. This suggests that the two phenomena are specifically related to each other. These data represent further evidence of the possible pathophysiological relevance of the neuroendocrine-immune feedback.