Mononucleosis
Kissing disease or mononucleosis occurs only in young adults. Epstein-Barr virus in the mononuclear cells may stimulate the growth of these cells. Since the effect of the assumed natural specific clone inhibitor is believed to be strongly reduced in young adulthood the infection may lead to abnormal growth stimulation of infected mononuclear cells in this age group and development of symptoms of mononucleosis.
The fact that the incidence of mononucleosis drops significantly after young adulthood indicates an increase of the effect of the assumed specific natural clone inhibitor