Immunological link between primary graft dysfunction and chronic lung allograft rejection

Abstract

Background: Primary graft dysfunction (PGD) in the immediate post-lung transplant period strongly increases the risk of chronic rejection (broncholitis obliterans syndrome). Here, we hypothesized that PGD-induced inflammation augments alloimmunity, thereby predisposing to broncholitis obliterans syndrome.

Methods: Primary graft dysfunction and broncholitis obliterans syndrome were diagnosed according to the established International Society for Heart and Lung Transplantation criteria. Anti-human leukocyte antigen (HLA) alloantibodies were analyzed using Flow-PRA. Donor HLA class II-specific T cells were analyzed using interferon (IFN)-gamma ELISPOT. Serum levels of 25 cytokines and chemokines were measured using LUMINEX.

Results: Of the 127 subjects, 29 (22.8%) had no PGD (grade 0), 42 (33.2%) had PGD-1, 36 (28.3%) had PGD-2, and 20 (15.7%) had PGD-3. Patients with PGD grades 1 to 3 (PGD(1-3)) had elevated proinflammatory mediators MCP-1, IP-10, interleukin (IL)-1 beta, IL-2, IFN-gamma, and IL-12 in the sera during the early posttransplant period compared with patients with PGD grade 0 (PGD(0)). On serial analysis, PGD(1-3) patients revealed increased development of de novo anti-HLA-II (5 years: 52.2% versus PGD(0) 13.5%, p = 0.008). However, no difference was found in anti-HLA-I alloantibody development (PGD(1-3) patients 48% versus PGD(0) 39.6%, p = 0.6). Furthermore, PGD(1-3) patients had increased frequency of donor HLA class II-specific CD4(+) T cells [(91.4 +/- 19.37) x 10(-6) versus (23.6 +/- 15.93) x 10(-6), p = 0.003].

Conclusions: Primary graft dysfunction induces proinflammatory cytokines that can upregulate donor HLA-II antigens on the allograft. Increased donor HLA-II expression along with PGD-induced allograft inflammation promotes the development of donor specific alloimmunity. This provides an important mechanistic link between early posttransplant lung allograft injury and reported association with broncholitis obliterans syndrome.

Figure 1

Upregulation of cytokines in the patients with PGD. Serum levels of 25 cytokines and chemokines were analyzed during the early post-transplant period in patients with and without PGD. A) Sampling time points for cytokine analysis were similar between the study groups (p=0.33). B) Pro-inflammatory chemokines IP-10 and MCP-1 and cytokines IFN-γ, IL-1β, IL-2, and IL-12 were found to be elevated in patients with PGD (black bars) compared to those without PGD (white bars). The difference in the serum levels of cytokines were statistically significant (p<0.05 for all). All values are expressed as pg/ml.

Figure 1

Upregulation of cytokines in the patients with PGD. Serum levels of 25 cytokines and chemokines were analyzed during the early post-transplant period in patients with and without PGD. A) Sampling time points for cytokine analysis were similar between the study groups (p=0.33). B) Pro-inflammatory chemokines IP-10 and MCP-1 and cytokines IFN-γ, IL-1β, IL-2, and IL-12 were found to be elevated in patients with PGD (black bars) compared to those without PGD (white bars). The difference in the serum levels of cytokines were statistically significant (p<0.05 for all). All values are expressed as pg/ml.

Figure 2

Development of alloantibodies in PGD patients. Serial analysis of A) HLA class I and B) II alloantibodies detected by Flow-PRA in study patients. The development of HLA antibodies was similar in patients with PGD, regardless of grade. Therefore, patients with PGD grades 1-3 were classified together (thick solid line) and compared with patients with no PGD (grade 0, thin short broken line). All patients included in the study were negative for HLA alloantibodies prior to transplant.

Figure 2

Development of alloantibodies in PGD patients. Serial analysis of A) HLA class I and B) II alloantibodies detected by Flow-PRA in study patients. The development of HLA antibodies was similar in patients with PGD, regardless of grade. Therefore, patients with PGD grades 1-3 were classified together (thick solid line) and compared with patients with no PGD (grade 0, thin short broken line). All patients included in the study were negative for HLA alloantibodies prior to transplant.