ACETYL CHOLINESTERASE IS EXPRESSED IN THE FOLLICULAR DENDRITIC CELLS OF GERMINAL-CENTERS - DIFFERENCES BETWEEN NORMAL AND NEOPLASTIC FOLLICLES

Acetyl cholinesterase (AcChE) was demonstrated by histochemistry in th e follicular dendritic cells (FDCs) of the germinal centres of lymph n odes, tonsils, and bowel lymphoid tissue. Its presence in the FDCs was confirmed by double immunostaining for CD21 or DRC-1. AcChE-positive FDCs are concentrated in the inner portion of the light zone of the ge rminal centre, being absent from the dark zone. In the lymphoid tissue surrounding the germinal centres are AcChE-positive blood vessels; do uble staining shows that the AcChE is present in the pericytes surroun ding the endothelium of the blood vessels. In contrast to the reactive follicle, the AcChE reactivity in FDCs of follicle centre lymphoma is absent or minimally expressed, although the dense FDC mesh is well st ained with CD21 or DRC-1. This suggests that the AcChE is not constitu tively expressed in FDCs but that its expression is influenced by the state and activity of the lymphoid cells in the germinal centre. The r educed level of AcChE staining can be profitably employed in the diagn osis of follicle centre lymphoma.