Ectopic B-cell clusters that infiltrate transplanted human kidneys are clonal

Abstract

B cells and their immunoglobulin products participate in allograft rejection of transplanted human kidneys in which an interesting feature is the presence of a germinal center like B-cell clusters in the allograft. We report here that the immunoglobulin repertoires of these infiltrating B cells are highly restricted and the B cells within a cluster are clonal. Antibody libraries made from the infiltrating B cells of individual patients unexpectedly revealed that each patient utilizes a particular set of dominant germ line genes as well as dominant complementarity determining region 3. Comparison of kidney and peripheral blood from the same patient showed that the immunoglobulin genes from both compartments had dominant clones, but they differed. The lymphocytes that infiltrate the kidneys express the immunoglobulin gene somatic recombination machinery usually restricted to highly activated lymphocytes in germinal centers and lymphomas. An analogy can be made between the inescapable antigenic drive in chronic infection versus that in an allograft, both of which may lead to emergence of dominant B-cell clones and even lymphoid malignancy.

Fig. 1.

The infiltrating B cells in biopsy tissues and RT-PCR of rag1, rag2, and TdT genes. (A) Section stained by hematoxylin and eosin. (B–D) The clusters of infiltrating mononuclear cells stained by hematoxylin and eosin. (E) The infiltrating B cells stained by anti-human CD20 monoclonal antibody. (F) PCR products of rag1 gene. (G) PCR products of rag2 gene. (H) PCR products of TdT gene. Lanes: 1, DNA marker; 2, 3, and 4 were three lymphomas genome DNAs as positive controls; 5, TX biopsy; 6, TX peripheral blood; 7, CAN biopsy; 8, CAN peripheral blood; 9 and 10 were negative controls. Neither lanes 9 nor 10 contained any cDNA, whereas lane 9 contained primers only.

Fig. 2.

In situ hybridization with the dominant CDR3 probe from CAN. (A) Nuclei were stained blue by DAPI. (B) Positively bound infiltrating B cells stained red by mouse anti-biotin-phycoerythrin monoclonal antibody. (C) The merge of A and B. (D) Another stained region of the same tissue section. (E) The nucleotide sequence of CDR3 probe and somatic mutations.