Immunopathologic aspects in human onchocercal lymphadenitis.

Lymph nodes (LN) from 50 patients with generalized onchocerciasis with or without diethylcarbamazine treatment and LN of patients with untreated localized onchocerciasis were studied. Light and electron microscopic examinations and immunostaining (PAP) were performed. In both forms of the disease the majority of microfilariae were degenerated and surrounded either by eosinophils or macrophages. In addition increased number of mast cells and plasma cells was observed. A direct contact between eosinophils and microfilariae, degranulation of eosinophils and free eosinophil granules in the electron dense material around the degenerating microfilariae were registered. The majority of plasma cells produced IgE or IgG. A positive staining for IgE was also present on the surface of mast cells. An extensive hyperplasia of the follicles was a characteristic feature in localized as well as treated generalized onchocerciasis. After anti-IgE staining a heavy intercellular deposition suggesting trapping of immune complexes by dendritic reticular cells developed in the light parts of the germinal centres. Not seldom, IgE producing blast cells were found in the follicles.