Detection of B lymphocytes (CD20+) in renal allograft biopsy specimens.

Acute allograft rejection represents an important complication after transplantation with significant impact on long-term graft survival. The involvement and relevance of B lymphocytes in this process is still not clear. The aim of this study was to quantify in renal allograft biopsy specimens the number of cells positive for CD20, a specific marker for B lymphocytes. Immunohistochemical techniques using monoclonal anti-CD20 antibody was used on paraffin sections from 38 renal allograft biopsy specimens. The biopsy specimens were classified into 3 groups, according to clinical and histological criteria: normal kidney, acute rejection, and chronic allograft nephropathy (CAN). In the normal kidney, no CD20(+) cells were detected. In contrast, in all cases of acute rejection and CAN, there were CD20(+) cells. The CD20(+) cells occurred in the infiltrate in 2 distinct patterns: scattered or nodular. In cases of acute rejection, the number of CD20(+) cells was significantly higher than in CAN cases (137.0 +/- 57.2 vs 45.4 +/- 9.8 cells/mm(2); P < 0.05). The nodular pattern was observed in 4 of 11 cases (36%) in the acute rejection group, and in 4 of 20 cases (20%) in the CAN cohort. In the acute rejection group, the presence of B-cell clusters tender to be associated with a higher level of serum creatinine (3.7 +/- 1.8 mg/dL vs 2.8 +/- 0.1 mg/dL in the scattered pattern group; not significant [ns]). In conclusion, these preliminary results demonstrated B lymphocytes in cases of renal allograft dysfunction, which were more pronounced in acute allograft rejection. Further analyses are required to determine whether the detection of CD20(+) cells in renal allograft biopsy specimens can be used as a prognostic marker.