The role of delayed hypersensitivity in granulomatous reactions to mycobacteria: 1. Relationship of delayed reaction size to severity of granulomatous reactions after intradermal injections of mycobacteria

Effect of antimacrophage serum on dermal tuberculin sensitivity and allergic pulmonary granuloma formation in rabbits

Anti-rabbit alveolar macrophage goat serum (AMS), adsorbed of hemolysins and hemagglutinins, exhibited complement-dependent cytotoxicity for the following rabbit target cells: alveolar macrophages, thymocytes, and kidney (RK-13) cells. The intravenous injection of AMS, sufficient to reduce markedly the dermal tuberculin reaction in BCG-sensitized rabbits, did not suppress the development of BCG-induced chronic and accelerated pulmonary granulomas. These observations are discussed in relation to delayed sensitivity, allergic granuloma formation, and cell-associated immunity.

Experimental granulomatous inflammation: the ultrastructure of the granuloma induced by injection of tubercle bacilli into Freund adjuvant-sensitised guinea-pigs

Injection of killed tubercle bacilli into a sensitised guinea pig produces a characteristic biphasic response with the development of an organised epithelioid cell granuloma in the second phase. Previous sensitisation to tubercle bacilli is a requirement for development of the organised granulomatous response. The main components of the granuloma are epithelioid cells, although multinucleate cells of both Langhans and foreign-body type are present. Epithelioid cells appear to evolve from monocytes, probably in the sequence: (a) monocyte, (b) monocytic transition form, (c) immature epithelioid cell, (d) mature epithelioid cell, although some may possibly develop through a macrophage stage. Differentiation of monocytes into epithelioid cells is a continual process in the experimental tuberculous granuloma with monocytes migrating into the lesion at all stages examined. Epithelioid cells are not obviously phagocytic. Their differ4ntiation has a phase suggestive of biosynthesis during which RER is the predominant cytoplasmic component. This is followed by a storage/secretory phase in which the cytoplasm contains membrane-lined vesicles and prominent Golgi apparatus. The vesicles and, where distended, the RER laminae contain a lightly staining, finely granular material the biological activity of which is unknown.

Experimental granulomatous inflammation: II. Effect of injection of intact and disrupted killed tubercle bacilli into Freund adjuvant-sensitized Cavies

The reaction of Freund adjuvant-immunized cavies to subsequent injection of Mycobacterium tuberculosis H37Ra is confirmed as an immunologically mediated phenomenon. Ultrasonic disruption of mycobacteria to be injected as "challenge" markedly increases the intensity of the consequent 24-48 h reaction and subsequent fibrosis in Freund adjuvant-sensitized cavies and has an apparently inhibiting effect on the extent of subsequent granuloma formation with marked reduction of the density of epithelioid cells. From this study, the 24-48 h reaction to injection of M. tuberculosis into sensitized animals appears clearly to be separable from subsequent granuloma formation depending upon the integrity or otherwise of the injected myocobacteria used as the challenge injection material.

Experimental granulomatous inflammation: I. Gross and light microscopical observations in freund adjuvant-sensitized Cavies following the injection of killed tubercle bacilli

The tuberculous granuloma, induced by injection of microgram doses of killed mycobacteria into guinea pigs sensitized by injection of Freund adjuvant is immunologically mediated. Formation of the granuloma is preceded by development within 24 h of a lymphocyte-dominated mononuclear cell response typical of a delayed hypersensitivity (type IV immune response) reaction. About the sixth day, following a marked decrease in intensity of the cellular reaction, a nodule containing monocytes and macrophages develops at the injection site. With increasing numbers of monocytes and macrophages the nodule forms a non-caseating granuloma with giant cells but dominated by epithelioid cells and reaching a maximum size about 3 wk after injection. Thereafter the granuloma undergoes gradual demolition being replaced and surrounded by fibroblasts and collagen deposition. The very delayed nature of this immune response as well as its histological character appear clearly to separate it from classical cell-mediated and humoral immune responses. These facts justify the hypothesis of a third type of (usually protective) immune response characterized histologically by the development of an epithelioid cell granuloma and determined by the nature of the antigenic material and the reactivity of the host. The initial polymorphonuclear leucocyte reaction to injection of mycobacteria, being similar in sensitized and control animals, does not appear to be under immunological control.