Experimental study on the mechanisms of delayed hypersensitivity reaction, with special reference to emigration and function of mononuclear cells.

Abstract

Delayed hypersensitivity reaction is characterized by Infiltration of mononuclear cells (macrophages and lymphocytes). The mechanisms of emigration and function of mononuclear cells in local skin lesions were studied in experimental tuberculosis. A chemotactlc activity for mononuclear cells was found in the extract of tuberculin skin sites, and proteases active at pH 3, 6, and 9 were found in the extract and partially purified using ammonium sulfate and column chromatography. Relationship between chemotactlc activity and protease activities was discussed. Similar protease activities were found in the extract of sensitized lymph node cells, and proteases active at pH 6 and 9 were increased when homo‐genate of sensitized lymph node cells was Incubated with PPD for 3 hours at 37°C. It appears that PPD could concern to release protease from sensitized lymphocytes and involve in delayed hypersensitivity reactions. The role of mononuclear cells in tuberculous skin lesions were studied in the sense of bacteriocidal activity for tubercle bacilli. Certain macrophages in the skin lesions were produced locally by cell division. Macrophages in granulation tissue around necrotic foci were specifically matured and strongly active for/9‐galactosidase, and the number of acid fast bacilli in macrophages and the intensity of staining for /3‐galactosidase were reversely correlated. This was also confirmed in irradiated rabbits with 400 rads of whole body radiation. These findings suggest that high levels of lysosomal enzymes are involved in destruction of bacilli.