MAST-CELLS IN ONCHOCERCOMAS FROM PATIENTS WITH HYPERREACTIVE ONCHOCERCIASIS (SOWDA)

In onchocerciasis, variations of the host's immune responsiveness prod uce a spectrum of clinical manifestations ranging from the common gene ralized to the rare hyperreactive form (sowda). For further characteri zation of the immune response, the localization and frequency of mast cells in onchocercomas from untreated and ivermectin-treated patients with hyperreactive onchocerciasis from Liberia and the Yemen were anal ysed and compared to the generalized form by immunohistochemistry with antibodies specific for human mast cell tryptase and chymase, histami ne and IgE. The nodules were selected with special regard to only one pair of live, microfilariae-producing Onchocerca volvulus. Throughout the nodular tissue of the hyperreactive form, mast cells accumulated i n the strong inflammatory infiltrates, especially near eosinophils and around cellular attacks on microfilariae as well as perivascularly. T heir number was significantly higher in the whole nodular tissue compa red to the generalized form. The highest numbers occurred in the nodul e centre. Mast cells carried IgE and appeared activated. No mast cells were observed in the cystic parts or attached to adult worms or micro filariae. In onchocercomas, 1 and 3 days after treatment with ivermect in, microgranuloma formation by eosinophils and macrophages around dam aged microfilariae was enhanced and accompanied by numerous mast cells . Attacks of neutrophils were also pronounced, but attacks by mast cel ls were not observed. In conclusion, hyperreactivity against microfila riae in onchocercomas clearly correlates with a strong mastocytosis an d IgE production parallel to tissue eosinophilia. (C) 1998 Elsevier Sc ience B.V. All rights reserved.