Changes in serum IgD in cigarette smokers.

Serum IgD levels in 83 healthy adults were measured by a radioimmunoassay technique and analysed according to each subject's smoking habit. The IgD geometric mean in cigarette smokers was twice as high as in non-smokers (408.6 vs 202.0 micrograms/dl). Serum IgD levels of 1,000 micrograms/dl or greater were noted in 22% of smokers but in none of the rare smokers or non-smokers. In the smokers group, the highest mean IgD level was found in those who did not actively inhale the smoke (762.6 micrograms/dl), followed by that in moderate smokers (563.8 micrograms/dl), and was lowest in heavy smokers who inhaled the smoke (283.0 micrograms/dl). The number of years a person smoked did not appear to have a significant effect on IgD levels. In ex-smokers, the mean IgD level (199.8 micrograms/dl) was similar to that in non-smokers, suggesting reversibility of the IgD changes following cessation of smoking. It seems prudent that the smoking habit should be taken into consideration in the interpretation of serum IgD levels.