[Antigen L, a new antigen from tubercle bacilli active in delayed hypersensitivity in animals sensitized with living bacilli (B.C.G.)]. / L'antigène L, nouvel antigène tuberculeux actif en réaction d'hypersensibilité retardée chez l'animal sensibilisé par des bacilles vivants (Bacille B.C.G.).

This report described the occurrence of an antigen in the tubercle bacilli. The antigen, designated antigen L, was mainly active in delayed hypersensitivity reaction in Guinea Pigs sensitized with living bacilli such as the B.C.G. strain. It was found in cultures filtrates of bovine strains as well as the human strains of tubercle bacilli.

Search of a standard for the titration of antigen L.

The Antigen L is made of the 10 p.100 TCA precipitable proteins that remained after 2 p.100 TCA proteins precipitation of a live BCG culture filtrate. It is 6 times more active in guinea pigs sensitized by living BCG than by inactivated BCG. The reference tuberculin (BR6) is the fraction retained by DEAE-Cellulose chromatography of the purified TP tuberculin described elsewhere (2). The kinetic study of BR6 using guinea pigs sensitized by live or inactivated BCG showed that between the 2nd and 4th month, BR6 had the same activity in both cases in respect to the diameter of the erythema reactions. Therefore, BR6 may serve as reference for the Antigen L between the 2nd and 4th month of sensitization.

Evaluation of difficulties in the standardization of human and bovine tuberculins.

The tuberculins are made of mixtures of antigens. Certain elements are common to all tuberculins, others are particular to each one. Bovine and human tuberculins are widely different. This is the reason why the activities of a bovine tuberculin using a human tuberculin standard will be in a ratio of 1 to 5 according to whether the guinea-pigs were sensitized with human or bovine mycobacteria. Also, the activities measured for a given tuberculin might be different if the mycobacteria used in sensitization were inactivated or not, depending on the amount of Antigen L in the tuberculin or in the standard. Because BCG is well defined and used worldwide we propose that a new standard be prepared from BCG cultures, and that the animals be sensitized by live BCG. Two new units are proposed: Bovine Clinical Unit (B.C.U.) and Human Clinical Unit (H.C.U.).

[Comparative dose-effect relationship of a tuberculin standard on guinea pig sensitivity, using living and dead tuberculosis bacilli]. / Loe dose-effet comparative d'une tuberculine étalon sur cobayes sensibilisés soit par bacilles tuberculeux vivants, soit par bacilles tués

The sensitization of guinea pigs utilized for tuberculin titration may be obtained by a BCG primo-vaccination followed by an inoculation of live, virulent Myc. tuberculosis. This method, which results in a sub-evolutive form of tuberculosis, gives a satisfactory sensitization level but has the disadvantage of utilizing animals which are germ carriers and therefore dangerous. A method has been tested employing killed germs (Jamaica strain) coated with Freund's complete adjuvant H37Ra which utilizes animals presenting no danger in handling. The results of 105 titrations made on 453 guinea pigs during two years show that the reactions obtained are clear, easy to read and remain stable over a long period (F equals 0.1). The comparison of values thus obtained shows that in the case of killed bacilli in relation to live bacilli: the mean dimensions of the reaction with 5, 10 and 20 IU are significantly more important (P is less than 0.0001) and the dose-response slope is significantly steeper (P is less than 0.01) which offers more precise results. Sensitization by killed germs therefore offers the double advantage of handling non-dangerous animals and obtaining results which are more precise and easier to read.