QUANTIFICATION OF PERIPHERAL BLOOD MICROCHIMERISM AND CORRELATION WITH DONOR ANTIGEN-SPECIFIC HYPOREACTIV1TY IN LUNG AND KIDNEY TRANSPLANT RECIPIENTS. C McSherrv, AM Jackson, K Butters, M Diko, and NL Reinsmoen, Department of Surgery, University of Minnesota, Minneapolis, MN. The identification of peripherally located donor cells in individuals who have undergone solid-organ transplantation has lead to speculation as to the tolerogenic role of circulating donor cells and to the possible significance of persistent donor alloantigen-presenting cells in inducing and maintaining an alloantigen-specific unresponsive state. Previously, we have shown that donor antigen-specific hyporeactivity (DASH) is a useful marker for identification of recipients with improved long-term graft function. The purpose of this study was to determine whether observed levels of peripheral blood microchimerism (PBMC) correlate with DASH and with clinical outcome in lung and in kidney transplant (tx) recipients. Detection of PBMC was accomplished with a PCR-based limiting detection assay utilizing HLA-DR sequence-specific primers. We studied 19 lung recipients (recips) > 12 mo posttx and 22 kidney recips ([email protected]
12-18 mo posttx, and [email protected]
3-6 yr posttx). PBMC was found in 55% of lung recips and 24% of kidney recips. To determine whether the level of PBMC correlates with development of DASH and with clinical outcome, a method for quantification of allogeneic microchimerism has been developed. Amplification occurs in the presence of 33p, and is followed by autoradiography and direct scintillation counting (enabled through utilization of 3rd party calibration curves). PBMC+ lung recips who were hyporesponsive had higher levels of circulating donor cells ( > 1:6,000) than those who were responsive. PBMC Level [range] # Lung Recips DASH+ Chronic Rej. > 1:6,000 [1:770 --, 1:5,400] 6 6 0 < 1:6,000 [1:8,300 --, 1:17,000] 4 0 2 PBMC not detected 9 0 3 In kidney recipients, the level of PBMC detected was generally much lower than that observed in lung recips; therefore correlation with DASH and clinical outcome was more difficult to discern. We are currently testing additional recipients at serial time points. Our data in lung recipients suggest that a minimum level of circulating donor antigen correlates with maintenance of donor antigen-specific hyporeactivity and a chronic rejection-free state.
MICROCHIMERISM IN R E N A L A L L O G R A F T R E C I P I E N T S . BF Duffy, Y Alevy, D Phelan, L Jones, S Shenoy, C Anderson, M W Flye and T Mohanakumar, Barnes Hospital H L A Laboratory and Washington University School of Medicine, Depts. of Surgery and Pathology, St. Louis, MO In order to investigate the role of chimerism in renal allografi survival and to determine whether donor specific blood transfusion provides any advantage towards induction o f chimerism we retrospectively analyzed renal allografi recipients who received different protocols of immunosuppression ie, DST with prednisone and imuran or non-DST with cyclospofine, prednisone and imuran. Donor H L A - D R was examined in recipient blood lymphocyte genomic D N A using PCR amplification and Southern Blot Analysis. Five DST recipients (7-10 years post tx) and 10 non-DST recipients (2-4 years post tx) were studied. The number of H L A antigens matched in both groups were similar, 0-4/6 and 0-3/6 respectively for DST and non-DST. All five DST recipients demonstrated chimefism. Three of five recipients had reversible rejection episodes during the early post transplant period. However, two & t h e s e DST recipients are undergoing chronic rejection. In contrast to the DST recipients, chimerism was found in only 5 of 10 o f the non-DST recipients and there was no correlation between number of rejection episodes and chimefism (2/5 for chimeric, 3/5 for non-chimeric). Thus, this preliminary analysis suggests DST regimen may provide an advantage in the induction of chimerism. The detection ofchimefism in the circulation does not correlate with long term function of allografi in DST or number &rejection episodes in both DST and non-DST recipients. H L A disparity has no apparent bearing in the development o f chimerism.