Determination of acceptable HLA mismatches in highly sensitized patients by soluble HLA class I ELISA inhibition.
BACKGROUND
Acceptable HLA mismatches for highly sensitized patients are determined so as to increase their chances of receiving transplants. The disadvantage of the current procedures is that the antibody reactivity of the patients' sera is tested against HLA antigens expressed on cells or HLA antigens isolated from cell lysates. Therefore, two (homozygous for HLA-A and -B) to four (heterozygous for HLA-A and -B) different HLA class I antigens are present in the test. This might cause reactivity toward nonacceptable mismatches to mask the determination of acceptable mismatches.


METHODS
Recently we observed that the detection of soluble HLA class I antigens is inhibited by HLA-specific antibodies. In the present study, inhibition of soluble HLA-specific ELISAs (anti-soluble HLA-A2, -B7, -B12) was evaluated as a tool used to determine acceptable mismatches. The results were compared with current determination of acceptable mismatches (which is by complement-dependent cytotoxicity and/or fluorescence-activated cell sorter analysis).


RESULTS
In the case of acceptable mismatches determined by conventional methods, sera from the patients were not interfering in these ELISAs, whereas in the case of nonacceptable mismatches (thus specific antibodies), significant inhibition was observed in most instances. Among the nonacceptable mismatches, the test showed significant inhibition in 20 of 24 cases, whereas among acceptable mismatches, no inhibition was observed (in eight of eight), indicating the lack of specific antibodies.


CONCLUSIONS
In highly sensitized patients, the introduction of soluble HLA-specific ELISAs is of additional and confirmatory value for the determination of acceptable mismatches. The major advantage of this approach is that antibody reactivity is tested against single antigens only.
Koelman
C A
CA
Department of Immunohematology and Blood Bank, Leiden University Medical Center, The Netherlands. Koelman@rullf2.medfac.leidenuniv.nl
van Beelen
E
E
Witvliet
M D
MD
Doxiadis
I I
II
Claas
F H
FH
D000906:Antibodies / Q000276:immunology; D000918:Antibody Specificity; D001788:Blood Grouping and Crossmatching; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006680:HLA Antigens / Q000097:blood*; D015395:Histocompatibility Antigens Class I / Q000097:blood*; D006650:Histocompatibility Testing; D006801:Humans; D007114:Immunization; D012995:Solubility
D000906:Antibodies; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I