Immunologic shin titration in leprosy patients and contacts.

A method of studying delayed-type hypersensitivity was developed with specific antigen in leprosy patients and contacts, measuring the dose-response curve at different lepromin concentrations. This "immunologictitration" is highly efficient for discriminating the degree of hypersensitivity reactions among the groups tested. With respect to the Fernandez reaction, the results obtained showed that there was a similar behavior in all groups studied, except in the tuberculoid group which had a more intense response, four times higher than that yielded by contacts of lepromatous patients. In the Mitsuda reaction, a similar behavior was also found among the different groups, except with respect to the reactivity intensity of contacts of lepromatous patients. Here it was demonstrated that this group had a significant depression in response to M. leprae antigen when compared with that from the other groups, independent of the degree of consanguinity or closeness to bacilliferous cases. In order to explain this immunosuppression in contacts of lepromatous patients, a hypothesis is proposed. It is suggested that changes could occur in M. leprae derived from lepromatous patients, diminishing their capacity to produce an adequate immune response.