Lepromin hypersensitivity induced by integral lepromin in persons presumably free from leprosy

RESUMO

1- A study has been made of the results of two successive lepromin tests in residents of San Miguel de Tucumán aged 20 years or more, supposedly healthy (except for various dermatologic conditions) and without known contacts with leprosy. The second-test injections were made 21 days after the first ones, at the time of reading of the Mitsuda reaction. The reactions of hypersensitivity (Fernandez) and of resistance (Mitsuda) are compared. 2- In the first test the frequency of the reaction of hypersensitivity in the 214 persons in whom it was read was 11.7 per cent, and the frequency of the reaction of resistance in the 92 persons who returned for that reading was 96.7 per cent - results which are not uncommon for noncontact adults. 3- In the second test special attention was paid the Fernandez reaction, because so few had been MItsuda negative that there could be no significant numerical changes in the retesting. Of the 57 original Fernandez negatives, 56.1 per cent now gave positive reactions, as did 6 of the 7 in whom the first reactions had been of doubtful grade. 4- A comparative study of the reactions of hypersensitivity anc of resistance among those in whom both reactions were read shows that (a) Those who gave negative results with both reactions were relatively few in both tests, 5.6 per cent in the first one and 3.9 per cent in the second. (b) Those who in the first test gave negative hypersensitivity but positive resistance reactions were many, 73.2 per cent, but in the second test only 15.7 per cent, a large proportion of the Fernandez negatives having been sensitized by the first injection. (c) The proportion of cases showing both reactions positive in the first test was not high, only 21.1 per cent, but it increased greatly, to 81.4 per cent, in the second test because of the large number who had acquired hypersensitivity. 5- The great discordance between the two reactions in the first test (73.2%), cjhanged to marked concordance (84.3%) in the second one. In other words, the persons under study reacted to the second injection of lepromin in much the same way as do leprosy contacts on first test. (3). 6- From the results observed it is concluded that, in persons without known contact and presumably free from leprosy, a single injection of integral lepromin can sensitize an appreciable proportion (well over 50%) of Fernandez-reaction negatives so that they become positive reactors.