76-P

Abstract

Our previous results demonstrated that 200 μg complement fixing antibodies (Abs) to MHC class I (cfAbs) or non-complement fixing Abs (ncAbs) result in obliterative airway disease (OAD) in mouse model of intrabronchial anti-MHC administration. In human lung transplantation, recipients may develop both complement fixing and non-complement fixing DSA that may augment chronic rejection. The aim of this study was to test if low levels of cfAbs and ncAbs can synergize leading to OAD. Low dose anti-MHC class I ncAbs mouse IgG1 (100 μg) or cfAbs IgG2a (25 μg) were given alone or in combination intrabronchially in F1 C57Bl/6 × B.10 mice on day 0,1,2,6 and weekly after. Isotype IgG were given in control. Lungs analyzed by histopathology. Serum tested for Abs to Kalpha1Tubulin (K α 1T) and collagenV (ColV) by ELISA. IFNγ, IL17 and IL10 cells specific to Kα1T and ColV enumerated by ELISPOT. Cytokines and growth factors in lung determined by RTPCR. Low dose of ncAbs (100 μg) or cfAbs (25 μg) alone did not lead to OAD including isotype control. Combination of ncAbs and cfAbs at same low dose resulted in OAD with cellular infiltration, fibrosis and luminal occlusion of vessels and bronchioles. Mice given both ncAbs and cfAbs developed serum Abs to Kα1T (667 ± 63 μg/mL, p = 0.065) and ColV (323 ± 41, p = 0.0034) compared to ncAbs alone, cfAbs alone or isotype mice. This was associated with increased IFNγ (p = 0.002), IL17 (p = 0.004) specific to Kα1T and ColV and suppression of IL10 compared to other groups. Further, there was upregulation of TGFβ, MCP-1, IL-6, IL-1β and VEGF. High dose ncAbs and cfAbs to MHC lead to OAD, but low dose of ncAbs or cfAbs given alone did not induce OAD. However, low levels of ncAbs and cfAbs in combination, can synergize and potentiate each other resulting in activation of inflammatory and fibrotic cascades leading to OAD. Hence, in human lung transplant recipients low titers of de novo DSA which are cfAbs and ncAbs may synergize augmenting chronic lung allograft rejection.