Factors of delayed hypersensitity in pulmonary tuberculosis

In a study of delayed hypersensitivity in 54 patients with pulmonary tuberculosis who were on specific treatment, 33 patients could not be sensitized to dinitrochlorobenzene (DNCB) although 25 of these were tuberculin (PPD) positive. The majority of the patients also had positive skin reactions to another recall antigen, streptokinase-streptodornase. To exclude a drug effect on DNCB reactivity, 40 untreated patients were studied. Twenty-six (65 per cent) of these did not show DNCB reactivity. The cause for nonsensitization to DNCB was not clear. There was no abnormality in the number of T lymphocytes in the peripheral blood of 28 patients.