The inflammatory exudate in delayed hypersensitivity

Abstract

So far, the delayed immune reactions have been the least understood of all antigen-antibody reactions. Recent investigations have shown that they have profound biological functions in conditions in which the defense against macromolecules recognized as foreign is a central factor. The histological changes have been studied, particularly by biopsy, but the cellular exudate has been almost ignored. The exudate in delayed immune reactions had not, before the present investigation, been the subject of systematic studies by the skin window technique. All the experiments were carried out on human subjects. Delayed hypersensitivity reactions were produced experimentally by using heteroantigens (DNCB, tuberculin, and diphtheria toxoid), normal homologous lymphocytes, and autoantigen from thyroid extract in patients with Hashimoto's thyroiditis. The exudate in the delayed cellular processes was found to differ considerably from the nonspecific inflammatory exudate-basophilic and to a lesser extent eosinophilic leukocytes being a new and constant finding, especially during the second day of reaction. They were not observed in concurrent control experiments on the same subject with physiological saline or in nonsensitized subjects. In Walzer's immediate reaction the exudate did not differ in cellular sequence from that in nonspecific reactions. On the basis of these experiments it may be permissible to advance the hypothesis that the basophilic leukocyte acts as a biological amplifier in delayed immune reactions, which are constantly taking place in the organism, in which cellular integrity is to be maintained and foreign antigens appear. The basophilic cells may convert certain stimuli, induced by antigen-antibody reactions, to chemical responses. Persistent liberation of histamine affords the possibility of an afflux of immunologically competent cells. A supply of acid mucopolysaccharides increases the connective tissue content of amorphous compounds and possibly organizes edema fluid into a gel. The aim of the reactions appears to be, in particular, limitation and, if possible, elimination of the foreign antigens from the organism.