Graft dysfunction in chronic antibody-mediated rejection correlates with B-cell-dependent indirect antidonor alloresponses and autocrine regulation of interferon-γ production by Th1 cells

Abstract

Chronic antibody-mediated rejection, a common cause of renal transplant failure, has a variable clinical phenotype. Understanding why some with chronic antibody-mediated rejection progress slowly may help develop more effective therapies. B lymphocytes act as antigen-presenting cells for in vitro indirect antidonor interferon-γ production in chronic antibody-mediated rejection, but many patients retain the ability to regulate these responses. Here we test whether particular patterns of T and B cell antidonor response associate with the variability of graft dysfunction in chronic antibody-mediated rejection. Our results confirm that dynamic changes in indirect antidonor CD4⁺ T-cell responses correlate with changes in estimated glomerular filtration rates, independent of other factors. Graft dysfunction progressed rapidly in patients who developed unregulated B-cell-driven interferon-γ production. However, conversion to a regulated or nonreactive pattern, which could be achieved by optimization of immunosuppression, associated with stabilization of graft function. Functional regulation by B cells appeared to activate an interleukin-10 autocrine pathway in CD4⁺ T cells that, in turn, impacted on antigen-specific responses. Thus, our data significantly enhance the understanding of graft dysfunction associated with chronic antibody-mediated rejection and provide the foundation for strategies to prolong renal allograft survival, based on regulation of interferon-γ production.

Keywords: B lymphocyte; ELISPOT; chronic allograft nephropathy; indirect alloresponses; interferon-γ.

Figure 1

ΔeGFR in PROTCL and BFC subgroups and combined group. Box plots show median and IQR, with whiskers representing data within 1.5 the IQR of the upper and lower quartiles, with outliers >1.5 and <3.0 IQR as + and >3.0 IQR as *. Horizontal lines to right of box plots indicate the mean value. Nine patients with BFC who either had missing follow-up data (n = 2), or eGFR <20 ml/min per 1.73 m² at time of biopsy (n = 7) have been excluded (Supplementary Table S1c). The “combined” group includes all patients with PROTCL and BFC, and have been split into “deteriorating” and “stable” subgroups, based on the relationship to the median ΔeGFR in each of the PROTCL and BFC subgroups. *Deteriorating group contains patients with ΔeGFR below or equal to the median in each of PROTCL and BFC groups (n = 27). The median ΔeGFR in this subgroup is −14.4 ml/min per 1.73 m² (IQR 15.5). Stable group contains patients with ΔeGFR above the median from each of the PROTCL and BFC groups (n = 25). The median ΔeGFR for this group is 0.3 ml/min per 1.73 m² (IQR 6.0). **Mann-Whitney U test.

Figure 2

Association between ELISPOT patterns and ΔeGFR over the course of the study in combined PROTCL and BFC group. Box plots show median and IQR, with whiskers representing data within 1.5 of the IQR of the upper and lower quartiles, with outliers >1.5 and <3.0 IQR as + and >3.0 IQR as *. Horizontal lines to right of box plots indicate the mean value. (a) Patterns grouped according to DSR versus NDSR status. Time point 1: Patients with ELISPOT showing DSR have median ΔeGFR of −8.0 ml/min (IQR 11.6) and mean ΔeGFR of −9.6 ml/min (SD ±12.6). Patients with NDSR have median ΔeGFR of −5.8 ml/min (IQR 17.9) and mean ΔeGFR of −8.0 ml/min (SD ±14.4). P = 0.70 Mann-Whitney U. Time point 2: Patients with ELISPOT showing DSR have median ΔeGFR of −10.1 ml/min (IQR 15.5) and mean ΔeGFR of −11.3 (±SD 10.9) ml/min. Patients with NDSR have median ΔeGFR of −3.1 ml/min (IQR 11.9) and mean ΔeGFR of −5.1 ml/min (SD ±13.4). P = 0.05 Mann-Whitney U. NB: Analysis with 2 outliers at time point 2 removed (ΔeGFR −33.7 [ID 392] and 44.2 [ID 958] both in NDSR group) and replaced with missing data reveal P = 0.015. (b) Patterns group according to evidence on ELISPOT of B-cell–dependent antidonor reactivity. Time point 1: Patients with ELISPOTs showing evidence of B-dependent antidonor IFN-γ production have median ΔeGFR of −8.3 ml/min per 1.73 m² (IQR 15.2) and mean ΔeGFR of −11.5 (SD ±15.0 ml/min per 1.73 m²). Patients with ELISPOT showing no evidence of B-dependent IFN-γ production have median ΔeGFR of −0.9 ml/min (IQR 17.9) and mean ΔeGFR of −4.0 (SD ±15.6) ml/min. P > 0.11 Mann-Whitney U. Time point 2: Patients with ELISPOTs showing evidence of B-dependent IFN-γ production have median ΔeGFR of −7.9 ml/min per 1.73m² (IQR 11.7) and mean ΔeGFR of −9.6 (SD ±10.9 ml/min per 1.73 m²). Patients with ELISPOT showing no evidence of B-dependent IFN-γ production have median ΔeGFR of −0.9 ml/min (IQR 11.6) and mean ΔeGFR of −4.1 (SD ±15.4) ml/min. P = 0.053 Mann-Whitney U. NB: Analysis with 3 outliers at time point 2 removed (ΔeGFR −33.7 [ID 392] and −44.2 [ID 958] both in “No evidence of B-dependency” group, and ΔeGFR −35.3 [ID 635] in “Evidence of B-dependency” group) and replaced with missing data reveal P = 0.01.

Figure 3

Multivariate logistic regression models in patient subgroups. ROC curves corresponding to the multivariate logistic regression models for linked groups of predictive variable in the PROTCL biopsy (a), BFC (b), and the optimized treatment BFC-CAMR subgroup with deteriorating creatinines (c), using generalized linear models to estimate each of the models, followed by elastic net estimate the optimal combined algorithm, with cross validation for parameter tuning. The predictive variables included in each of the models are listed in Supplementary Tables S5 and S6.

Figure 4

Associations between patterns on ELISPOT and changes in eGFR in BFC cohort. Box plots showing the association between the results of ELISPOT assays at time of biopsy and follow-up sample with graft outcome in patients who had viable PBMC samples after thawing at both times (n = 27). (a) Patients with BFC with NDSR at time of biopsy (n = 16), showing stability for those who remained NDSR (n = 11) compared with those who became DSR (n = 5, P = 0.003) and (b) patients with BFC with DSR at time of biopsy, showing stable eGFR for those patients who were DSR at time of biopsy (n = 11) but converted to NDSR (n = 8), compared with progressive decline among those who remained DSR (n = 3, P = 0.0001). (c,d) Box plots show median and IQR, with whiskers representing data within 1.5 the IQR of the upper and lower quartiles, with outliers >1.5 and <3.0 IQR as + and >3 IQR as *. Horizontal lines to right of box plots indicate the mean value. Graphs shows the association between the changes in ELISPOT assays from time point 1 to time point 2 with graft outcome in patients who had 2 viable PBMC samples that could be fully interpreted (i.e., had results from CD8-, CD19-, CD25-, and CD8–CD25-depleted PBMC) (n = 37). (c) Antidonor responses. Groups correspond to those shown in Table 6 and Supplementary Table S8. Patients at time point 1 with no evidence of B-dependent antidonor responses who maintained evidence of regulated responses at time point 2 had a median ΔeGFR of 1.8 ml/min per 1.73 m² (IQR 6.6) and mean ΔeGFR of 1.2ml/min per 1.73 m² (SD ±12.3). Patients with evidence of B-dependent antidonor responses at time point 1 who maintained evidence of regulated responses at time point 2 had a median ΔeGFR of −5.5 ml/min per 1.73 m² (IQR 12.9) and mean ΔeGFR of −8.6 ml/min per 1.73 m² (SD ±13.7). Finally, patients who had unregulated B-cell–dependent antidonor responses at time point 2 had a median ΔeGFR of −10.1 ml/min per 1.73 m² (IQR 13.7) and mean ΔeGFR of −14 ml/min per 1.73 m² (SD ±12) irrespective of the pattern they had at time point 1. P = 0.036. (d) Antiviral responses. Groups correspond to those shown in Supplementary Tables S9 and S10. Groups compared by Kruskal-Wallis test. MDRD, Modification of Diet in Renal Disease.

Figure 5

Flow cytometric analysis of Th-1 cytokine production. (a,b) Donor antigen-specific IFN-γ production by CD4+ T cells: comparison of subgroups according to functional B-cell phenotype on ELISPOT. CD8-depleted PBMCs were stimulated with donor antigen under same conditions as in ELISPOT, then assayed by flow cytometry by using a cytokine capture system. White bars: Samples (n = 8) from patients with ELISPOT pattern showing evidence of B-dependent antidonor IFN-γ production (with or without evidence of regulation). Black bars: Samples (n = 3) from patients with ELISPOT pattern showing only suppression of antidonor IFN-γ production by B cells with NO evidence of B-dependent responses. (a) Shows the percentage of CD4+ cells expressing only IFN-γ (IFN-γ + IL-10−) or coexpressing with IL-10 (IFN-γ + IL-10+). (b) Shows the comparison of the percentage of total cells expressing IFN-γ/% total cells expressing IL-10. (c–e) Polyclonal stimulation with anti-CD3/anti-CD46 monoclonal antibodies: comparison of subgroups according to functional B-cell phenotype on ELISPOT. White bars: Samples (n = 4) in which antidonor-specific ELISPOT showed only suppression of antidonor IFN-γ production by B cells with NO evidence of B-dependent responses. Black bars: Samples (n = 8) in which antidonor-specific ELISPOT showed evidence of a regulated B-dependent antidonor response. Gray bars: Samples (n = 4) in which antidonor-specific ELISPOT showed evidence of an unregulated B-dependent antidonor response. (c) Percentage of CD4+ cells staining for IFN-γ alone (IFN-γ + IL-10−) compared with cells staining for both (IFNγ + IL-10+). (d) Median fluorescence intensity of staining for IFN-γ or IL-10 in the single-positive (IFNγ + IL-10−) or double-positive (IFNγ + IL-10+) CD4+ populations as indicated. (e) Ratio of mean fluorescence intensity of IFN-γ staining to IL-10 staining in the double-positive (IFN-γ + IL-10+) population in (d). *P < 0.05 by Mann-Whitney U test.