Summary. An improved model of granulomatous inflammation in skin was developed by second passage skin grafting of isolated, lyophilized skin granulomas, originally elicited in naive mice by inoculations of lyophilized hepatic schistosome egg granulomas. The tissue reaction is caused by a single exposure to a noninfectious, acellular granulomagenic stimulus and occurs in healthy mice free of systemic disease. The model should prove useful for isolation of granuloma initiation factor(s). Furthermore, because there is a time lag before new granuloma formation begins, a window exists for analytical dissection of the initiation process. In this study we described the responses of host cells by autoradiography, and light and electron microscopy. The activity of angiotensin-converting enzyme and proline-specific endopeptidase showed a modulation during granuloma formation. In addition we found that severe immunosuppression with high dose cyclosporine therapy did not alter granuloma formation, supporting the idea that initiation of organized granulomas is T-cell independent.Key words. Skin granuloma model; granulomatous inflammation; T-cell independent; granuloma; angiotensin-converting enzyme; proline-specific endopeptidase.Granulomatous inflammation is a characteristic pathological feature of certain diseases such as sarcoidosis, tuberculosis and leprosy. The most representative animal model has been hepatic lesions of experimental murine schistosomiasis, which has been widely used for morphological, immunological and biochemical studies 1,2. Recently, Nishimura et al. a and Okamoto et al.4 established a skin model by transplanting fresh and lyophilized hepatic granulomas, respectively, into the skin of naive mice. The skin model has distinct advantages over the hepatic model since the mice with skin granulomas do not suffer from systemic effects of the ongoing parasitic infection, and the granulomagenic stimulus is introduced only once, allowing examination of a time course of the changes. However, the lyophilized hepatic granulomas contain parasite products, such as soluble egg antigen, which might influence tissue reactions. We now report an improved model in which skin granulomas appearing after first passage in mice are isolated, lyophilized and grafted into the skin of a second generation of naive host mice.
Material and methodsFemale C57BL/6 strain mice (5-6 weeks old) were infected with Schistosoma mansoni and hepatic granulomas isolated from mice after nine weeks by the method of Nishimura et al. 3.5 The granulomas were frozen in an acetone/dry ice mixture and thawed in running tap water. After repeating the process for 2 cycles they were frozen and dried using a Unitorap II (Virtis, New York). The lyophilized sample was wet with distilled water and about 50 mg inoculated into first passage subcutaneous tissue of the dorsum of healthy naive mice. Five weeks later, granulomas which developed in the skin were separated from surrounding tissue, minced, lyophilized, and grafted into the skin of naive mice. The ski...
