A Histochemical Analysis of Mononuclear Cell Infiltrates of the Skin with Particular Reference to Delayed Hypersensitivity in the Guinea Pig

Abstract

Mononuclear cells in exudates in the skin due to delayed type hypersensitivity have been subdivided into 2 groups on the basis of their content of lysosomes. Lysosomes were demonstrated in the cytoplasm by their content of the enzyme acid phosphatase. Macrophages were found to contain many lysosomes but these cytoplasmic structures were scanty in lymphocytes. It was therefore possible to compare the number of roacrophages with the number of lymphocytes in mononuclear cell exudates in the skin. Four systems were studied, delayed hypersensitivlty induced by the intradermal injection of tuberculin, diphtheria toxoid and human gamma globulin and contact sensitivity due to the application of the chemical sensitizing agent dinitrochlorobenzene. In all 3 delayed hypersensitivity reactions due to the intradermal injection of antigen macrophages and small lymphocytes were present in equal numbers at the peak of the reaction 24 hr. after injection whereas in the contact sensitivity reaction at 24 hr. lymphocytes formed 80% of the mononuclear cells.