Presented at:
XIX Int'l Congress
Transplantation, Miami, FL, Aug 25-30, 2002
Myeloid pDC1 is decreased as compared to plasmacytoid pDC2 lineage in peripheral blood of patients successfully withdrawn from immunosuppression after liver transplantation
G. Mazariegos, A. Zeevi, A. Zahorchak, L. Ostrowski, B. Flynn, A. Logar, I. Dvorchik, J. Reyes, A. Thomson
University of Pittsburgh, Thomas E. Starzl Transplantation Institute
Aim : To examine whether predominance of the putatively tolerogenic dendritic cell (DC) 2 subset correlates with clinical tolerance following liver transplantation (LTx).
Methods : PBMC from patients who have been successfully withdrawn from immunosuppression following LTx (Group A), those who are undergoing prospective drug weaning (Group B), and those in whom drug withdrawal failed or has not been attempted (Group C) were isolated from peripheral blood by Ficoll density centrifugation. Total DC were identified as HLA-DR + and lineage marker (CD3, CD14, CD19, CD20) negative on four-color flow cytometric analysis. Subpopulations of IL-3R alpha HLA-DR+ lin-{precursor (p)DC2} and CD4+ CD11c+ HLA-Dr+ lin-(pDC1) were further quantified. 10 adults served as healthy controls.
Results : 12 clinically stable patients with normal liver function were eligible for study. Mean age at transplantation was 12.7 years (range 0.4-48). Diagnoses at LTx included biliary atresia (n=2), metabolic disease (n=3), autoimmune disease (n=3), cholestatic syndromes (n=2), and Wilson's Disease and cryptogenic cirrhosis (n=2). Group A patients have been off immunosuppression for a mean of 2.2 yr. (range 0.2-7.1) and were weaned off drugs by physician direct protocol (n=1) or emergently for infectious disease indications (n=3). Group B patients are undergoing uninterrupted drug weaning for a mean of 1.8 yrs. Group C patients failed drug withdrawal due to rejection or recurrent autoimmune disease (n=2) or never had drug withdrawal attempted because of adverse rejection history or h/o autoimmune disease (n=2). Mean patient demographic data, % DC, and DC subsets with ranges are listed in Table 1. Statistical analysis was by Mann-Whitney U test with significance at p<0.05.
| Group | A. Off Immunosuppression | B. Prospective Weaning | C. Drug Withdrawal Failed or Not Attempted | Normal Adult Controls |
| # of pts | 4 | 4 | 4 | 10 |
| Age @ LTx (yr.) | 4.4 (0.4-7.3) | 2.1 (0.6-3.5) | 32 (19-48) | N/A |
| Time post LTx (yr.) | 9 (1.8-18) | 7.5 (4.5-9.7) | 10.3 (3-17) | N/A |
| Current age (yr.) | 13.4 (2.2-25) | 9.5 (8-12.9) | 42 (23-64) | 34 (25-53) |
| Current Time Off Drugs/Weaning (yr) | 2.2 (0.2-7.1) | 1.8 (0.2-4.6) | N/A | N/A |
| %pDC | 2.4 (1.1-3.9) | 1.3 (0.8-2.4) | 3.2 (2.2-3.8) | 2.9 (.8-5.6) |
| % DR+, lin-, CD11c-, CD123- |
24.7 (11-38.9) | 21.6 (13-29) | 11.3 (5-23) | 14 (3-37) |
| %pDC2 | 15.3 (6.3-24.6)# | 12.5 (0.1-19.1) | 6.1 (2.3-12.4) | 14 (8-33) |
| %pDC1 | 54.4 (45-61.6)* | 43.5 (0.3-66.4) | 78.1 (68.9-85.8) | 63 (21-85) |
| %pDC2/%pDC1 | 0.3 (0.1-0.4)^ | 0.3 (0.2-0.4) | 0.08 (0.03-0.17) | 0.3 (.1-.8) |
| ** Group A vs. Group C: *p<0.03; #p < 0.12; ^p<0.06 N/A= not applicable | ||||
Conclusion : This preliminary investigation suggests that the myeloid DC lineage (pDC1) is less prevalent in patients successfully withdrawn from immunosuppression as well as in those on low levels of immunosuppression undergoing prospective drug weaning as compared to those patients requiring ongoing maintenance immunosuppression. Further studies to confirm these findings and better characterize tolerant liver allograft recipients are ongoing in a larger patient population.
Acknowledgment This research was performed as a project of the Immune Tolerance Network, a seven year clinical research project headquartered at the University of California San Francisco and supported by the National Institute of Allergy and Infectious Diseases, the National Institute of Diabetes, and Digestive and Kidney Disease and the Juvenile Diabetes Research Foundation.