"Results: The results confirmed transient increases in adrenaline and prolactin plasma concentrations. Sexual arousal and orgasm increased the absolute number of leukocytes, in particular natural killer cells (CD3-CD16+CD56+), in the peripheral blood. In contrast, T cell (CD3+) and B cell (CD3-CD20+) subpopulations as well as the production of interleukin 6 and tumor necrosins factor alpha remained unaffected by sexual activity. Conclusion: These findings demonstrate that components of the innate immune system are activated by sexual arousal and orgasm."