Natural Killer Activity and Its Changes among Participants in a Smoking Cessation Intervention Program. A Prospective Pilot Study of 6 Months' Duration

We examined the effect of smoking cessation on natural killer (NK) activity of peripheral blood lymphocytes in terms of a prospective study of 27 Japanese subjects who participated in a smoking cessation intervention program. This program was delivered by means of groupcounseling offering 7 sessions of about 2 hours over 6 months to help smokers to discontinue the habit. Thirteen subjects ceased smoking (quitters), while 14 continued to smoke (cigarette smokers). NK activity before the intervention was correlated positively with age (correlation coefficient=0.46, P