Studies on granuloma formation in Syrian hamsters experimentally infected with Schistosoma mansoni

The formation of granuloma in Syrian hamsters was studied. The granulomatous reaction started with accumulation of T-cells which subsequently attract the eosinophils by their products, then aggregation of eosinophils and neutrophils around the living egg(s) to destroy egg shell. Consequently, the eosinophils immediately attack the miracidium and release their cytotoxic products to dissolve it. Later on, the macrophages accumulate, in cooperation with eosinophils, release their fibrogenic factors, stimulate the formation of granulomatous tissue and ultimately fibrosis takes place. The dissolving of both egg shell and miracidium by eosinophilic products proves their ability to deal with both egg shell (hard part) and the miracidium itself (soft part) and this confirms their great ability to play a main role in the immunity against helminthic infection. The different morphological variations of the granuloma are included and the role of other inflammatory cells is also discussed.