Clinical relevance of low levels of preformed alloantibodies detected by flow cytometry in the first year post-kidney transplantation.
OBJECTIVE
To determine the prevalence of transplants performed with a false-negative cytotoxicity cross-match and to analyze the clinical relevance of alloantibodies (Ab) detected only by flow cytometry (flow).


METHODS
We studied 66 patients undergoing kidney transplantation from a cadaveric donor. All patients had a simultaneous negative T+AHG+DTT and B+DTT. Pretransplant sera were retrospectively analyzed by flow cytometry according to an Emory University protocol: (1) T+ and B-: Ab anti-class I; (2) T- and B+: anti-class II; (3) T+B+: anti-class I + II. Chi-square, Fisher exact, Student t test, and Kaplan Meier analyses were employed with significance assigned at P < or = .05.


RESULTS
The overall incidence of false-negative cytotoxicity was 33.3% (22/66), namely, 6.1% (n = 4) anti-class I; 9.1% (n = 6) anti-class II; and 18.2% (n = 12) anti-class I + II. Primary nonfunctioning grafts occurred in 6.8% (3/44) and 13.6% (3/22) negative and positive flow patients (two anti-class I + II and one class II; P = .39). The incidence of graft loss in the first year was respectively, 13.6% (6/44) and 18.2% (4/22; two anti-class II and two anti-class I + II; P = .72). Compared to flow-negative grafts, creatinine levels were significantly higher among flow-positive patients at 8 and 12 weeks. One-year graft survivals were 86.4% among negative versus 81.8% for the positive group (P = .67).


CONCLUSIONS
We observed that 33% of kidney transplant recipients had low levels of alloantibodies detected only by flow. This single factor was associated with the worst graft function in the first trimester with a suggestion of a higher risk for non-functioning graft.
Michelon
T
T
Pathology Department Graduate Studies, FFFCMPA and Transplant Immunology Laboratory, Santa Casa Hospital, Porto Alegre, Brazil. tatimich@yahoo.com
Schroeder
R
R
Fagundes
I
I
Canabarro
R
R
Sporleder
H
H
Rodrigues
H
H
Silveira
J
J
Montagner
J
J
Garcia
V
V
Neumann
J
J
Graudenz
M
M
D002102:Cadaver; D003602:Cytotoxicity, Immunologic; D005188:False Negative Reactions; D005434:Flow Cytometry; D005500:Follow-Up Studies; D006084:Graft Rejection / Q000453:epidemiology; D006085:Graft Survival / Q000276:immunology; D006681:HLA-D Antigens / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D007518:Isoantibodies / Q000097:blood*; D016030:Kidney Transplantation / Q000276:immunology* / Q000401:mortality; D016019:Survival Analysis; D014019:Tissue Donors; D016896:Treatment Outcome
D006681:HLA-D Antigens; D015395:Histocompatibility Antigens Class I; D007518:Isoantibodies