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OR23 Antibodies to MICA, AT1R and endothelial cells occur independently in transplant patients and in sera
Abstracts / Human Immunology 77 (2016) 1–39
OR23
ANTIBODIES TO MICA, AT1R AND ENDOTHELIAL CELLS OCCUR INDEPENDENTLY IN TRANSPLANT PATIENTS AND IN SERA. Nicole M. Valenzuela, Jennifer Zhang, Michelle Hickey, Elaine F. Reed. UCLA, UCLA Immunogenetics Center, Los Angeles, CA, United States. Aim: We sought to understand the incidence of antibodies (Ab) to HLA, MICA, AT1R or endothelial cells (EC) in pre- and post-transplant patients, and whether such Ab present concurrently in patients and in single serum samples. Methods: We retrospectively analyzed clinical results from pre- and post-transplant patients tested for AT1R, MICA, HLA, and EC Ab, and evaluated single serum samples tested for multiple types of Ab to determine whether these Ab occur together. AT1R Ab were measured by quantitative ELISA; HLA and MICA Ab were detected by Luminex single antigen; Ab to EC were detected in a flow cytometric crossmatch against mature primary aortic EC (ECXM). Results: In transplant patients, the overall incidence of patients with Ab to EC was 43.2%, MICA Ab were seen in 9.9%, and 57.1% had AT1R Ab in at least one test. Regraft patients were more likely to exhibit EC or MICA Ab, particularly those with a deceased donor transplant compared with a living donor. HLA Ab were also correlated with anti-EC and MICA Ab. 78 serum samples were tested for all 3 non-HLA Ab. 26.9% of sera were negative for all three tests, while 1.3% were positive for all. There was no correlation between Ab to MICA and anti-EC Ab tested in the same serum. However, a majority of samples positive for ECXM also had AT1R Ab. AT1R Ab were significantly higher in sera that were positive for ECXM (28.8U/mL in ECXM+ vs. 19.4U/mL in ECXM-); however, 21.9% of samples without AT1R Ab were positive in ECXM, while 19% of samples negative for ECXM had very strong (>40 U/mL) AT1R Ab. Finally, in patients who had both ECXM testing and XMONE against potential donors, there was no apparent correlation between Ab to mature EC and donor specific endothelial precursors. Conclusion: HLA sensitized patients and regraft patients were more likely to have either EC or MICA Ab. The incidence of AT1R Ab was high; however, testing tended focus on high risk patients and may not reflect true incidence in the general transplant population. Serum with high AT1R Ab also tended to be positive for ECXM, but there were cases with strong AT1R Ab but negative ECXM. These results suggest that Ab to MICA, AT1R and EC are manifestations of different immune responses and a panel of non-HLA Ab testing is informative to identify different types of non-HLA Ab that may be detrimental graft survival.
OR24
RECIPIENT FCGR3A-158V HOMOZYGOUS GENOTYPE IS ASSOCIATED WITH AN INCREASED RISK OF CHRONIC LUNG ALLOGRAFT DYSFUNCTION. Haibo Sun 1, John R. Greenland 2,3, Dessislava Kopchaliiska 1, David D. Gae 1, Jonathan P. Singer 2, Jeffrey A. Golden 2, Steven R. Hays 2, Daniel Calabrese 2, Jasleen Kukreja 4, Raja Rajalingam 1.1Immunogenetics and Transplantation Laboratory, Department of Surgery, University of California San Francisco, San Francisco, CA, United States; 2Department of Medicine, University of California San Francisco, San Francisco, CA, United States; 3Medical Service, San Francisco VA Medical Center, San Francisco, CA, United States; 4Division of Cardiothoracic Surgery, Department of Surgery, University of California San Francisco, San Francisco, CA, United States. Aim: Chronic lung allograft dysfunction (CLAD) is a major obstacle in the long-term success of lung transplantation. Recipient natural killer (NK) cells substantially influence the immune response to the allografts. NK cells can respond to allograft via three distinct mechanisms: missing-self, induced-self, and antibody dependent cell cytotoxicity (ADCC). NK cell ADCC is regulated by CD16 (FcRIIIa), a low-affinity cell-surface receptor for the Fc portion of IgG antibodies. CD16 is encoded byFCGR3A, which carries a functional single nucleotide polymorphism that substitutes phenylalanine (F) for valine (V) at residue 158. Despite identical levels of CD16 expression, 158V homozygotes have higher binding affinity for IgG compared with 158F homozygotes. We hypothesized that the recipients carrying high binding FCGR3A-158V variants would have worse outcome compared to the weakly binding FCGR3A-158F carriers. Methods: We developed a melting curve based q-PCR method to analyze FCGR3A-V158F variants in a cohort of 252 lung transplant recipients. CLAD was determined by date of FEV1 or FVC drop to <80% of baseline and survival date were obtained from UNOS. CLAD-free survival was compared across FF, VV, and VF genotype recipients using Kaplan-Meier and Cox proportional hazard modeling methods. Results: Numbers of recipients with FCGR3A-158 FF, VV, and VF genotypes are 107 (42%), 30 (12%) and 115 (46%), respectively. CLAD-free survival was shorter in the 158VV group (3.0 median years) than the 158FF group (6.0 median years, HR 1.6, 95% CI 1.0-2.7, P = 0.05) and VF group (5.3 median years, ns) (Figure). Conclusions: We observed an association between theFCGR3A-158 VV genotype and worse CLAD-free survival. Recipients with this genotype would presumably have more NK cell-mediated ADCC activity and could be at increased risk of graft dysfunction in the context of donor-specific antibodies. Mechanistic studies and validation in other cohorts will be needed to determine the significance of this finding to lung transplant outcomes.
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OR23
ANTIBODIES TO MICA, AT1R AND ENDOTHELIAL CELLS OCCUR INDEPENDENTLY IN TRANSPLANT PATIENTS AND IN SERA. Nicole M. Valenzuela, Jennifer Zhang, Michelle Hickey, Elaine F. Reed. UCLA, UCLA Immunogenetics Center, Los Angeles, CA, United States. Aim: We sought to understand the incidence of antibodies (Ab) to HLA, MICA, AT1R or endothelial cells (EC) in pre- and post-transplant patients, and whether such Ab present concurrently in patients and in single serum samples. Methods: We retrospectively analyzed clinical results from pre- and post-transplant patients tested for AT1R, MICA, HLA, and EC Ab, and evaluated single serum samples tested for multiple types of Ab to determine whether these Ab occur together. AT1R Ab were measured by quantitative ELISA; HLA and MICA Ab were detected by Luminex single antigen; Ab to EC were detected in a flow cytometric crossmatch against mature primary aortic EC (ECXM). Results: In transplant patients, the overall incidence of patients with Ab to EC was 43.2%, MICA Ab were seen in 9.9%, and 57.1% had AT1R Ab in at least one test. Regraft patients were more likely to exhibit EC or MICA Ab, particularly those with a deceased donor transplant compared with a living donor. HLA Ab were also correlated with anti-EC and MICA Ab. 78 serum samples were tested for all 3 non-HLA Ab. 26.9% of sera were negative for all three tests, while 1.3% were positive for all. There was no correlation between Ab to MICA and anti-EC Ab tested in the same serum. However, a majority of samples positive for ECXM also had AT1R Ab. AT1R Ab were significantly higher in sera that were positive for ECXM (28.8U/mL in ECXM+ vs. 19.4U/mL in ECXM-); however, 21.9% of samples without AT1R Ab were positive in ECXM, while 19% of samples negative for ECXM had very strong (>40 U/mL) AT1R Ab. Finally, in patients who had both ECXM testing and XMONE against potential donors, there was no apparent correlation between Ab to mature EC and donor specific endothelial precursors. Conclusion: HLA sensitized patients and regraft patients were more likely to have either EC or MICA Ab. The incidence of AT1R Ab was high; however, testing tended focus on high risk patients and may not reflect true incidence in the general transplant population. Serum with high AT1R Ab also tended to be positive for ECXM, but there were cases with strong AT1R Ab but negative ECXM. These results suggest that Ab to MICA, AT1R and EC are manifestations of different immune responses and a panel of non-HLA Ab testing is informative to identify different types of non-HLA Ab that may be detrimental graft survival.
OR24
RECIPIENT FCGR3A-158V HOMOZYGOUS GENOTYPE IS ASSOCIATED WITH AN INCREASED RISK OF CHRONIC LUNG ALLOGRAFT DYSFUNCTION. Haibo Sun 1, John R. Greenland 2,3, Dessislava Kopchaliiska 1, David D. Gae 1, Jonathan P. Singer 2, Jeffrey A. Golden 2, Steven R. Hays 2, Daniel Calabrese 2, Jasleen Kukreja 4, Raja Rajalingam 1.1Immunogenetics and Transplantation Laboratory, Department of Surgery, University of California San Francisco, San Francisco, CA, United States; 2Department of Medicine, University of California San Francisco, San Francisco, CA, United States; 3Medical Service, San Francisco VA Medical Center, San Francisco, CA, United States; 4Division of Cardiothoracic Surgery, Department of Surgery, University of California San Francisco, San Francisco, CA, United States. Aim: Chronic lung allograft dysfunction (CLAD) is a major obstacle in the long-term success of lung transplantation. Recipient natural killer (NK) cells substantially influence the immune response to the allografts. NK cells can respond to allograft via three distinct mechanisms: missing-self, induced-self, and antibody dependent cell cytotoxicity (ADCC). NK cell ADCC is regulated by CD16 (FcRIIIa), a low-affinity cell-surface receptor for the Fc portion of IgG antibodies. CD16 is encoded byFCGR3A, which carries a functional single nucleotide polymorphism that substitutes phenylalanine (F) for valine (V) at residue 158. Despite identical levels of CD16 expression, 158V homozygotes have higher binding affinity for IgG compared with 158F homozygotes. We hypothesized that the recipients carrying high binding FCGR3A-158V variants would have worse outcome compared to the weakly binding FCGR3A-158F carriers. Methods: We developed a melting curve based q-PCR method to analyze FCGR3A-V158F variants in a cohort of 252 lung transplant recipients. CLAD was determined by date of FEV1 or FVC drop to <80% of baseline and survival date were obtained from UNOS. CLAD-free survival was compared across FF, VV, and VF genotype recipients using Kaplan-Meier and Cox proportional hazard modeling methods. Results: Numbers of recipients with FCGR3A-158 FF, VV, and VF genotypes are 107 (42%), 30 (12%) and 115 (46%), respectively. CLAD-free survival was shorter in the 158VV group (3.0 median years) than the 158FF group (6.0 median years, HR 1.6, 95% CI 1.0-2.7, P = 0.05) and VF group (5.3 median years, ns) (Figure). Conclusions: We observed an association between theFCGR3A-158 VV genotype and worse CLAD-free survival. Recipients with this genotype would presumably have more NK cell-mediated ADCC activity and could be at increased risk of graft dysfunction in the context of donor-specific antibodies. Mechanistic studies and validation in other cohorts will be needed to determine the significance of this finding to lung transplant outcomes.
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