7 8 Abstracts C-6.1 #143 STRATEGIES OF ANTIBODY CHARACTERIZATION, RA Gomez, EM Menchaca, WW Ward, TM Freeman, Transplant Immunology Section, Immunology Branch, Departments of Pathology and Medicine, Wilford Hall USAF Medical Center, Lackland AFB, TX. When faced with the "challenge" of highly sensitized patients on the cadaveric renal transplant waiting list, the HLA lab uses a variety of techniques to characterize the patient's antibody in order to determine transplantability. A small percentage of our patients have been awaiting renal transplant for years with PRA's consistently >90%. When attempts to reduce with DTT or autoadsorption offer no decrease in PRA, analysis for specificity is an impossibility. In light of this, we perform adsorptions with selected lymphocytes possessing certain HLA CREG or HLA antigens shared with previous grafts. By analyzing the removal of each separate antibody, we can attempt to decipher the puzzle of a > 90% PRA. The puzzle can then be put together piece by piece to determine acceptable and unacceptable antigens of possible organ donors. A strategic use of this technique along with other techniques available to HLA technologists can help characterize antibody specificities of patients with PRA's > 90%. Although we do not participate in a broad organ sharing program, the use of this information is a key factor in locating potentially compatible donors. C-6.1 #144 SIGNIFICANCE OF A B-CELL CROSSMATCH OVER A SIX-ANTIGEN MATCH. EM Menchaca, RA Gomez, WW Ward, TM Freeman, Transplant Immunology Section, Immunology Branch, Departments of Pathology and Medicine, Wilford Hall USAF Medical Center, Lackland AFB, TX. "KH" is a 50 year old oriental male awaiting a second renal transplant with a diagnosis of HTN. His HLA type is A2,11; B55; Cwl; DR4,8; DR53; DQ1,4. His previous graft was from a living related donor with Class I typing A26; B54,61; Cw1,3, transplanted in July 1983. In May 1992 the patient's T-cell percent reactive antibody was 68% and specificities found were A26, B40 and B18. A B-cell PRA done with platelet adsorbed sera showed 33% positive reactions. The specificity of the antibody was to DR5, DQ3(7). While most positive B-cell crossmatches are not caused by HLA-DR-DQ antibodies but by non-HLA antibodies, in the studies where HLA-DR-DQ antibodies have been implicated, most have shown a deleterious effect. Therefore, we believe this antibody to be a significant observation. Because of differences in racially associated HLA antigens, KH's HLA-DR4 antigen is associated with DQ4 (probably Dw15 as described in Japanese). This HLA-DR-DQ linkage has not been observed in caucasians. According to UNOS statistics, >80% of cadaveric donor kidneys are from whites. Because of the patient's DQ3 specificity, "KH" will crossmatch positive with a UNOS 6 antigen (A,B and DR) match offered with the usual DR4-DQ3 combination. Much information can be derived from B-cell screenings. Having good characterization of a B-cell antibody can be crucial to crossmatch interpretation in this setting.

Significance of a B-cell crossmatch over a six-antigen match

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Page 1: Significance of a B-cell crossmatch over a six-antigen match

7 8 Abstracts

C-6.1 #143

STRATEGIES OF ANTIBODY CHARACTERIZATION, RA Gomez, EM Menchaca, WW Ward, TM Freeman, Transplant Immunology Section, Immunology Branch, Departments of Pathology and Medicine, Wilford Hall USAF Medical Center, Lackland AFB, TX.

When faced wi th the "chal lenge" of h ighly sensit ized pat ients on the cadaveric renal t ransplant wai t ing list, the HLA lab uses a var iety of techniques to characterize the pat ient 's ant ibody in order to determine t ransplantabi l i ty .

A small percentage of our pat ients have been awai t ing renal t ransplant for years wi th PRA's consis tent ly > 9 0 % . When at tempts to reduce wi th DTT or autoadsorpt ion offer no decrease in PRA, analys is for speci f ic i ty is an impossibi l i ty. In l ight of this, we perform adsorpt ions wi th selected lymphocytes possessing certain HLA CREG or HLA ant igens shared wi th previous grafts. By analyzing the removal of each separate ant ibody, we can at tempt to decipher the puzzle of a > 90% PRA. The puzzle can then be put together piece by piece to determine acceptable and unacceptable antigens of possible organ donors.

A strategic use of this technique along wi th other techniques available to HLA technologis ts can help characterize ant ibody specif ic i t ies of patients w i th PRA's > 90%. A l though we do not part icipate in a broad organ sharing program, the use of this informat ion is a key factor in locat ing potent ial ly compat ib le donors.

C-6.1 #144

SIGNIFICANCE OF A B-CELL CROSSMATCH OVER A SIX-ANTIGEN MATCH. EM Menchaca, RA Gomez, WW Ward, TM Freeman, Transplant Immunology Section, Immunology Branch, Departments of Pathology and Medicine, Wilford Hall USAF Medical Center, Lackland AFB, TX.

"KH" is a 50 year old oriental male awaiting a second renal transplant with a diagnosis of HTN. His HLA type is A2,11; B55; Cw l ; DR4,8; DR53; DQ1,4. His previous graft was from a living related donor with Class I typing A26; B54,61; Cw1,3, transplanted in July 1983.

In May 1992 the patient's T-cell percent reactive antibody was 68% and specificities found were A26, B40 and B18. A B-cell PRA done with platelet adsorbed sera showed 33% positive reactions. The specificity of the antibody was to DR5, DQ3(7).

While most positive B-cell crossmatches are not caused by HLA-DR-DQ antibodies but by non-HLA antibodies, in the studies where HLA-DR-DQ antibodies have been implicated, most have shown a deleterious effect. Therefore, we believe this antibody to be a significant observation.

Because of differences in racially associated HLA antigens, KH's HLA-DR4 antigen is associated with DQ4 (probably Dw15 as described in Japanese). This HLA-DR-DQ linkage has not been observed in caucasians.

According to UNOS statistics, >80% of cadaveric donor kidneys are from whites. Because of the patient's DQ3 specificity, "KH" will crossmatch positive with a UNOS 6 antigen (A,B and DR) match offered with the usual DR4-DQ3 combination.

Much information can be derived from B-cell screenings. Having good characterization of a B-cell antibody can be crucial to crossmatch interpretation in this setting.