Antibody-mediated rejection is well established for renal allografts but remains controversial for lung allografts. Cardinal features of antibody-mediated rejection in renal allografts include antibodies to donor human leukocyte antigen (HLA) and evidence for antibody action, such as complement activation demonstrated by C4d deposition. We report a lung allograft recipient with circulating antibodies to donor HLA who failed treatment for acute cellular rejection but responded to therapy for humoral rejection. To address the second criteria for antibody-mediated rejection, we determined whether complement activation could be detected by measuring C4d in bronchoalveolar lavage fluid (BALF) by ELISA. Airway allergen challenge of asthmatics activates the complement pathway; therefore, we used BALF from asthmatics pre-and postallergen challenge to measure C4d. These controls demonstrated that ELISA could detect increases in C4d after allergen challenge. BALF from the index patient had elevated C4d concomitant with graft dysfunction and anti-donor HLA in the absence of infection. Analysis of BALF from 25 additional lung allograft recipients showed that C4d concentrations > >100 ng/mL were correlated with anti-HLA antibodies (p = = 0.006), but were also observed with infection and in asyptomatic patients. The findings support the occurrence of anti-HLA-mediated lung allograft rejection and suggest that C4d measurement in BALF may be useful in diagnosis.

BackgroundFibrosing mediastinitis (FM) is an idiosyncratic reaction to infection with Histoplasma capsulatum with a prevalence of 3:100,000 people infected. The rarity of post-histoplasmosis fibrosing mediastinitis (PHFM) in areas where H. capsulatum is endemic suggests that an abnormal immunological host response may be responsible for the development of fibrosis. Our group previously reported an association between subjects with PHFM and human leukocyte antigen (HLA)-A*02. We sought to confirm or extend those findings with application of high resolution HLA typing in a cohort of subjects with PHFM.MethodsHigh-resolution HLA typing was performed on DNA samples from a new cohort 34 patients with PHFM. Control cohorts included 707 subjects from the “European American” subset of the National Marrow Donor Program® (NMDP) and 700 subjects from Dialysis Clinic, Inc. (DCI). The carriage frequencies of the HLA alleles identified in the PHFM, NMDP, and DCI cohorts were calculated and then all were compared.ResultsWe found an increase in the carriage frequency of HLA-DQB1*04:02 in PHFM subjects relative to the controls (0.15 versus 0.07 in DCI and 0.05 in NMDP; p = 0.08 and 0.03). Multiple logistic regression showed that DQB1*04:02 was statistically significant (p = 0.04), while DQB1*03:02 and C*03:04 had point estimates of OR > 1, though they did not reach statistical significance. The HLA-A*02 association was not replicated.ConclusionsHLA-DQB1*04:02 is associated with PHFM, which supports the premise that an aberrant host immune response contributes to the development of PHFM.

Antibody-mediated rejection (ABMR) is implicated in 45% of renal allograft failure and 57% of late allograft dysfunction. Peritubular capillary C4d is a specific but insensitive marker of ABMR. The 2013 Banff Conference ABMR revised criteria included C4d-negative ABMR with evidence of endothelial-antibody interaction. We hypothesized that endothelial activation and lymphangiogenesis are increased with C4d-negative ABMR, and correlate with intra-graft T-regulatory cells (Tregs) and T-helper 17 (Th17). Seventy-four renal transplant biopsies were selected to include: a) ABMR with C4d Banff scores ≥2 (n=35); b) variable microvascular injury (MI) and C4d score <2 (n=24); c) variable MI and C4d score=0 (n=15). Controls included normal pre-implantation donor kidneys (n=5). Immunohistochemistry for endothelial activation [P- and E- selectins (SEL)], lymphangiogenesis (D2-40), Tregs (FOXP3), and Th17 (STAT3) was performed. Microvessel and inflammatory infiltrate density was assessed morphometrically in interstitium and peritubular capillaries. All transplants had significantly higher microvessel and lymph vessel density compared to normal. Increased expression of markers of endothelial activation predicted transplant glomerulopathy (P-SEL, p=0.003). Increased P-SEL and D2-40 were associated with longer interval from transplant to biopsy (p=0.005). All three markers were associated with increased interstitial fibrosis, tubular atrophy and graft failure (P-SEL, p<0.001; E-SEL, p=0.0011; D2-40, p=0.012). There was no association with the intragraft FOXP3/STAT3 ratio. We conclude that endothelial activation and lymphangiogenesis could represent a late response to injury leading to fibrosis and progression of kidney damage, and are independent of the intragraft FOXP3/STAT3 ratio. Our findings support the therapeutic potential of specifically targeting endothelial activation.

BackgroundDesensitization with IVIG and rituximab allows acceptable graft survival in sensitized kidney transplant recipients with preexisting donor-specific antibodies (DSAs) and a positive crossmatch. There is little published data reporting the durability of DSA removal in kidney transplant recipients treated with IVIG and rituximab.MethodsWe conducted a 3-year prospective DSA monitoring study in living donor kidney recipients with preexisting DSA to assess the durability of DSA removal after a perioperative protocol of IVIG and rituximab. All recipients had flow crossmatch titers less than 1:32. Data were analyzed using linear mixed effects models and Kaplan-Meier survival methods.ResultsThe longitudinal database comprised 210 mean fluorescence intensity (MFI) determinations. Forty-two DSAs were identified in 29 patients. Pretreatment MFI averaged 4715 ± 3962 (range, 947-20 129). At 1 month posttransplant, 18 patients (62%) had a complete response (MFI < 1000) and an additional 9 patients (31%) had a partial response (MFI reduced but >1000). There was a 46% reduction (P < 0.001) in DSA MFI at 1 month posttransplant that was sustained throughout the 3-year follow-up period and was observed for both class I and II DSAs regardless of pretreatment MFI levels. With a mean posttransplant follow-up of 1048 ± 574 days, 3-year patient and graft survivals were 95% and 90%. Four patients (14%) had acute rejection between days 125 and 560.ConclusionsDesensitization with IVIG and rituximab results in early and sustained DSA removal over a 3-year posttransplant period in living donor kidney transplant recipients with pretransplant DSA and a positive crossmatch, excellent patient and graft survivals and a low incidence of acute rejection.

Some polymorphisms on HLA molecules are shared by different HLA types, which allows us to group HLA molecules into 'families' or groups based on the shared epitope. These cross-reactive epitope groups (CREGs) can be used as a basis for matching donors to recipients for renal transplantation. The current allocation system uses HLA-B,DR mismatching for assigning HLA points. Graft survival using newer immunosuppressive drugs still shows a significant improvement in graft survival for 0-mismatched donors (3-year survival approximately 90%) and a significantly worse graft survival for 5 and 6 HLA-mismatched donors (3-year graft survival approximately 75%). However, the difference in graft survival between 1-, 2-, 3- and 4-mismatched donors are nor significantly different from each other (80-85% survival at 3 year). This has led to a reassessment of the UNOS allocation system and the need to re-evaluate the role of HLA in graft survival, minority allocation, and HLA sensitization. One of the problems with the current algorithm is that very few recipients are actually getting well-matched kidneys (approximately 3% get 1 mismatch and 10% get 2 mismatch). Transplant centres using the UNOS CREG variance (10 points awarded for 0 CREG, 0 DR mismatches) were able to find matches at a sixfold higher rate over 0 BDR mismatches. The size of the list affects the likelihood of finding a good match and the CREG variance was more successful in larger transplant programs. The effect of HLA on equity in renal allocation is also being addressed. There is some concern that HLA points may be at least partially responsible for the decreased transplant rate in African Americans. The 1999 UNOS data showed that 46.9% of the list were Caucasian, while 55.2% of the transplants were in Caucasian recipients. Conversely, African Americans made up 35.8% of the list and only 27% of the transplants went to African Americans. Since most of the donors were Caucasian (75.9% vs. 11.2%), it has been speculated that the Black population may be disadvantaged because they have less chance of getting HLA points. The impact of HLA on transplant rate is still being disputed and may not be a major factor since so few recipients actually benefit from the points given for BDR mismatches. However, CREG matching has the advantage of equalizing the HLA effect since rare HLA antigens are grouped with common HLA antigens sharing the same public epitopes. Another advantage for CREG matching is the protection from sensitization to HLA. The effect of HLA matching on sensitization is increased with each HLA match. Black recipients are more likely to be sensitized than Caucasians with the same level of mismatch. Also, once sensitized, Black recipients are less likely to get transplanted than Caucasians because of greater difficulty in finding a well-matched donor. Of patients transplanted with 0 CREG-mismatched donors, 82% remained unsensitized to Class I, compared with less than 60% in recipients who received greater than 2 BDR mismatches. The use of CREG matching in rena...