BAFF-R is expressed on B-cell lymphomas depending on their origin, and is related to proliferation index of nodal diffuse large B-cell lymphomas.

Abstract

B-cell activating factor receptor (BAFF-R) is one of three known receptors for BAFF. BAFF-R is required for B-cell maturation and survival. We tried to determine the normal pattern of BAFF-R expression in non-neoplastic and neoplastic B- and T-cells. We used immunohistochemistry to evaluate the expression pattern of BAFF-R in non-neoplastic and neoplastic lymphoid tissues of routinely fixed paraffin-embedded samples, and examined the relationships among BAFF-R and expressions of CD10, bcl-6, MUM-1, and MIB-1. BAFF-R expression was detected on B-cells of the mantle zones, some cells within germinal centers, and scattered cells in the interfollicular areas of reactive lymph nodes. BAFF-R expression was only found in B-cell lymphoma (60/120, positive samples/examined samples), but not in T/NK cell lymphoma (0/10) or Hodgkin lymphoma (0/10). The proportions were as follows : follicular lymphoma (14/16), diffuse large B-cell lymphoma (DLBCL) (27/61), mantle cell lymphoma (4/4), and Burkitt lymphoma (0/4). According to Hans' criteria, DLBCLs were subclassified into germinal center B-cell-like (GCB) and non-germinal center B-cell-like (non-GCB) types. Interestingly, in nodal lymphomas, in the GCB subgroup (n=12), 9 of 12 (75%) were positive for BAFF-R, while 6 of 20 (30%) were positive in the non-GCB subgroup (n=20) (p < 0.05). In addition, expression of BAFF-R related to lower MIB-1 index was associated with GCB-type DLBCL. In conclusion, BAFF-R was only found in some B-cell lymphomas, which was closely associated with the expression pattern in normal counterparts, although BAFF-R expression on follicular lymphoma is different from that on germinal center cells, which is similar to bcl-2. BAFF-R was rather specifically related to low growth activity of GCB-type DLBCL of nodal origin.