Increased plasma mannose binding lectin levels are associated with bronchiolitis obliterans after lung transplantation

Abstract

Background: Long-term lung allograft survival is limited by bronchiolitis obliterans syndrome (BOS). Mannose binding lectin (MBL) belongs to the innate immune system, participates in complement activation, and may predispose to graft rejection. We investigated mannose binding (MBL) during cold ischemia and in tissue samples from explanted lungs with BOS, and assessed MBL and complement proteins in plasma post-lung transplantation relative to BOS staging.

Methods: MBL was detected by immunohistochemistry lung tissue at the time of cold ischemia and in samples with BOS. MBL was assayed in the peripheral blood of 66 lung transplant patients transplanted between 1990-2007.

Results: MBL localized to vasculature and basement membrane during cold ischemia and BOS. Patients further out post-lung transplant > 5 years (n = 33), had significantly lower levels of MBL in the blood compared to lung transplant patients < 5 years with BOS Op-3 (n = 17), 1738 ± 250 ng/ml vs 3198 ± 370 ng/ml, p = 0.027, and similar levels to lung transplant patients < 5 years with BOS 0 (n = 16), 1738 ± 250 ng/ml vs 1808 ± 345 ng/ml. MBL levels in all BOS 0 (n = 30) vs. all BOS Op-3 (n = 36) were 1378 ± 275 ng/ml vs. 2578 ± 390 ng/ml, p = 0.001, respectively. C3 plasma levels in BOS 0 (n = 30) vs. BOS Op-3 (n = 36) were 101 ± 19.8 mg/ml vs. 114 ± 25.2 mg/ml, p = 0.024, respectively.

Conclusions: MBL localizes within the lung during graft ischemia and BOS, higher levels of plasma MBL are associated with BOS Op-3 and < 5 years post-transplant, and higher level of plasma complement protein C3 was associated with BOS Op-3 clinical status. MBL may serve as a biomarker for poorer outcome post-lung transplantation.

Figure 1

Immunohistochemistry for mannose binding lectin (MBL) in lung allograft tissue (10X) during cold ischemia as detected by anti-MBL antibody (mouse anti-human), DAB, and methylene green counterstain. MBL binds to airway basement membrane (star), A, alveolar capillary junctions (star), C, and endothelium (star) E. Isotype controls (mouse IgG1, κ) shown in B, D, and F, respectively.)

Figure 2

Immunohistochemistry for mannose binding lectin (MBL) in lung allograft tissue (10X) in explanted lung allograft tissue with bronchiolitis obliterans as detected by anti-MBL antibody (mouse-anti-human), DAB, and methylene green counterstain. MBL binds to remnant airway basement membrane(star), A and C, and vasculature (star), E. Isotype controls (mouse IgG1, κ) shown in B, D, and F, respectively.

Figure 3

Immunohistochemistry for mannose binding lectin (MBL) in lung allograft tissue (10X) in lung biopsies with non-transplant diffuse alveolar damage as detected by anti-MBL antibody (mouse-anti-human), DAB, and methylene green counterstain. MBL binds to airway basement membrane and alveolar spaces (star), A. Isotype control (mouse IgG1, κ) shown in B.

Figure 4

Mannose binding lectin levels in the peripheral blood of lung transplant patients transplanted > 5 years or < 5 years, with BOS 0 compared to BOS Op-3.Long-term > 5 years post-lung transplant patients (n = 33) had significantly lower levels of MBL in the blood compared to lung transplant patients < 5 years with BOS Op-3 (n = 10), 1738 ng/ml vs 3198 ng/ml, p = 0.027, A. Within the long-term > 5 years post-transplant cohort, patients with BOS 0 (n = 12) had significantly lower levels of MBL compared to those with BOS Op-3 (n = 21), MBL level 1,048 ng/ml vs 2186 ng/ml, p =0.007, B. Comparing all patients with BOS 0 (n = 29) vs. BOS Op-3 (n = 36), BOS 0 patients had significantly lower MBL and C3, 1378 ng/ml vs. 2578 ng/ml, p = 0.001, C.

Figure 5

Comparing all patients with BOS 0 (n = 29) vs. BOS Op-3 (n = 36), BOS 0 patients had significantly lower C3, 104 mg/ml vs. 114 mg/ml, p = 0.024, respectively, A. Within the long-term survivors cohort, patients with BOS 0 (n = 12) had significantly lower levels of MBL and C4 compared to those with BOS Op-3, C4 level 21.6 mg/ml vs 28.7 mg/ml, p = 0.038, B.