FcγRIIB is differentially expressed during B cell maturation and in B‐cell lymphomas

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Abstract
Summary: FcγRIIB, a low affinity receptor for the Fc portion of immunoglobulin G (IgG), is thought to drive negative selection of B cells in germinal centers (GC) by inducing apoptosis upon interaction with immune complexes. Its expression was investigated by immunohistochemistry in 22 reactive lymphoid tissues and 112 B‐cell lymphomas. Pre‐GC mantle cells, marginal zone cells and their neoplastic counterparts expressed FcγRIIB. The B chronic lymphocytic leukaemia (B‐CLL)/small lymphocytic lymphomas were also positive. Not detected in GC, FcγRIIB was expressed in 52% of follicular lymphomas and in 20% of diffuse large B cell lymphomas (DLBCL). In DLBCL, FcγRIIB expression was linked to transformation (P < 0·001). Re‐analysis of a gene profile data set from the Lymphochip microarrays showed that FcγRIIB expression in the activated B‐like DLBCL subgroup was higher than in the GC‐like one (P < 0·04), and was associated with an adverse prognostic both in univariate (P < 0·003) and in multivariate analysis including the International Prognostic Indicator (IPI) (P < 0·01). Thus these results challenge the potential role of FcγRIIB during B‐cell selection in GC, and suggest a prognostic value of FcγRIIB expression in DLBCL.