Comment: Interestingly, the immunoglobulin A, or IgA, immunity measure changed depending upon genital sexual activity frequency. Men and women who engaged in such activity 3 or more times per week had the lowest IgA readings, but the progression wasn’t linear:

IgA is an antibody that responds to foreign invaders in the mucus membranes, such as the vagina, mouth, lungs, etc.

Psychological Reports

94(3), 839–844.

Charnetski, C. J., & Brennan, F. X. (2004). Sexual Frequency and Salivary Immunoglobulin A (IgA)

112 college students reported the frequency of their sexual encounters and were divided into four categories: none, infrequent (less than once a week), frequent (one to two times per week), and very frequent (three or more times per week). Participants also described their overall sexual satisfaction. Saliva samples were collected and assayed for salivary immunoglobulin A (IgA). Individuals in the frequent group showed significantly higher levels of IgA than the other three groups, which were comparable. Data on length of relationship and sexual satisfaction were not related to the group differences.