Further studies of sensitivity to avian and human old tuberculin in man

Abstract

Summary It has previously been shown that, among non-BCG-vaccinated Royal Air Force apprentices aged 18–19, those who reacted to small doses of tuberculin tended to give larger reactions to human than to avian tuberculin; in those who reacted only to large doses of tuberculin, the reverse was found. This finding of a ‘cross-over’ in passing from small to large doses has now been confirmed in a further group of 130 non-BCG-vaccinated R.A.F. apprentices. No such cross-over was found in 147 old people aged 60–91, indicating that the cross-over in the young men was unlikely to be related to a long interval since previous infection. No cross-over was found in 37 young men, believed to have been infected with mammalian tubercle bacilli, and tested simultaneously with two doses of the human and two of the avian tuberculin; this indicated that the cross-over in the R.A.F. apprentices was unlikely to be inherent in the behaviour of these two tuberculins in man. It is concluded that in the R.A.F. apprentices the reactions to the small doses indicated past infections with human (or bovine) tubercle bacilli, whereas reactions only to the large doses indicated infection with avian (or related) tubercle bacilli.