Immunohistochemical study of low affinity Fc receptor for IgE in reactive and neoplastic follicles.

The distribution of low affinity IgE Fc receptors (FceR2, FceRII) in reactive and neoplastic follicles was studied by an indirect immunoperoxidase method with monoclonal antibody specifically reacting to FceRII (H107). The tissues examined in this study included lymph nodes, extranodal tissues of divergent diseases, and follicular lymphomas. In the germinal centers (GCs) of the lymph follicles. FceRII showed a lace-like pattern irrespective of the distribution of IgE. In general, FceRII was positive only in the light zone and not in the dark zone of GCs. The distribution of FceRII was different from that of DRC1(+) FDC which were FceRII(+) and FceRII(-). FceRII was seen by immunoelectron microscopy on the cell surface of follicular dendritic cells (FDCs). IgE-positive GCs in Kimura's disease and Warthin's tumor were intensely positive for FceRII in their entire portion. In IgE-positive GCs, an increased number of FceRII-positive lymphoid GC cells was recognized by immunoelectron microscopic observation. In follicular lymphoma, there were also two types of FDC which were FceRII(+) and FceRII(-). These findings indicated that FceRII on FDCs was closely related to the IgE immune response and also was a marker for functional phase or differentiation of FDCs.