Tuberculin reaction in children treated with isoniazid.

This study involved 370 children infected by Mycobacterium tuberculosis. Follow-up tests, three to nine years after a course of isoniazid treatment, showed that the tuberculin reactions remained strongly positive, although some fluctuation in size was observed. The persistence of tuberculin hypersensitivity in these patients was considered an asset, as delayed-type hypersensitivity and cell-mediated immunity are related closely, according to recent studies on antituberculosis immunology. With the risk of endogenous disease removed by isoniazid treatment, the patients gained a bonus of cell-mediated immunity to protect them from future exogenous reinfection.