probably T-cells. The cells that fight off bacteria and stuff. Anyhow, I like to smoke while i'm sick. It takes my mind off being sick, and lets me relax. If I have a cough, i'll smoke a bowl or two, and the coughing subsides for alittle while. Of course, when you have a cough, smoking isn't going to help cure it. That's the cost of smoking while sick. It slows your recovery.