Expansion and somatic hypermutation of B-cell clones in rejected human kidney grafts.
BACKGROUND
B-cell infiltrates are common in rejected kidney allografts, yet their composition is still unclear. The aim of our study was to characterize the clonal composition of B-cell infiltrates of rejected human kidney grafts.


METHODS
We used a molecular approach to characterize the partial B-cell repertoires of 5 failed human kidney grafts with detectable B-cell infiltrates. A comparison between the intragraft and blood repertoire was also conducted for 1 case.


RESULTS
Redundant sequences were observed in both blood and graft, although the level of clonal amplification was significantly higher for the graft. Somatic hypermutations (SHMs) were also more frequent in sequences found in the graft compared to the blood. The rate of nonsilent mutations was significantly higher in complementarity determining regions (CDRs) compared to framework regions in blood sequences as well as in graft sequences found at low frequency. In contrast, this preferential distribution was lost in sequences found at high frequency in the graft, suggesting a lack of affinity maturation in situ. Lastly, follicular dendritic cells were undetectable in CD20 infiltrates in all samples examined.


CONCLUSIONS
We provide here evidence that B-cell clones expand and undergo SHMs in situ. However, the even distribution of nonsilent SHM in high-frequency graft sequences together with the absence of follicular dendritic cells do not support the view that infiltrating B cells are part of functional germinal centers.
1 Transplant Center, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA. 2 Transplant Center, First Hospital of Jilin University, Changchun, China. 3 Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA. 4 Division of Transplant Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA. 5 Renal Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA. 6 Address correspondence to: Emmanuel Zorn, Ph.D., Massachusetts General Hospital, Transplant Center, Thier 807, 55 Fruit St, Boston, MA 02114.
Jack
J
Ferdman
Fabrice
F
Porcheray
Baoshan
B
Gao
Carolina
C
Moore
Julie
J
DeVito
Sarah
S
Dougherty
Margaret V
MV
Thomas
Evan A
EA
Farkash
Nahel
N
Elias
Tatsuo
T
Kawai
Sayeed K
SK
Malek
Stefan G
SG
Tullius
Waichi
W
Wong
Emmanuel
E
Zorn
D000293:Adolescent; D000328:Adult; D064591:Allografts; D018951:Antigens, CD20 / Q000378:metabolism; D001402:B-Lymphocytes / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D002478:Cells, Cultured; D002648:Child; D003713:Dendritic Cells / Q000166:cytology; D005260:Female; D006084:Graft Rejection / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012189:Retrospective Studies; D055815:Young Adult
D018951:Antigens, CD20