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Comparison of the biologic activity of tuberculins by the use of lymphocyte cultures.

Four lots of purified protein derivative of tuberculin with different potencies in skin testing were studied for their capacity to induce synthesis of deoxyribonucleic acid in cultures of lymphoctyes from human subjects vaccinated with bacillus Calmette-Guerin. When the uptake of [14C] thymidine by the lymphocytes was compared with the response to a reference preparation, 2 of the lots were found to be significantly stronger than the others. The results were essentially the same in 12 consecutive experiments and were in good agreement with results from skin tests in guinea pigs vaccinated with bacillus Calmette-Guerin. When used in this system in concentrations of 0.1 to 10 μg per ml, another lot of purified protein derivative of tuberculin had the same potency as the International Standard for PPD of Mammalian Tuberculin in contrast to results from skin tests in guinea pigs. The lymphocyte culture system appears to be useful for comparisons of the potency of tuberculins and other skin test reagents.