Christian Bach

Supplemental Figures 1-24 and Tables 1-3

Supplemental Figures 1-24 and Tables 1-3

IgA isotype antibodies (Ab) against human leukocyte antigens (HLA) recognize their target with high affinity as well as high avidity. Little is known about the influence of these IgA isotype Abs on organ graft survival after transplantation (Tx). For this study, sera from 276 kidney re-Tx candidates were selected who lost their transplanted organ in the past, and were listed on the waitlist of Erlangen/Nuremberg for a second Tx. The time to first dialysis after Tx (TtD), median, measured in months, was used as a precise endpoint marker for loss of graft function. IgG and IgA Abs were investigated using Luminex technology on generic (Luminex mixed test) and Ab specification (Luminex Single Antigen test) level. Of the 276 sera, 89 were tested positive for IgA and 243 for IgG Abs. Interestingly, within 86/89 sera, the presence of IgA Ab was significantly linked to the presence of IgG (p < 0.0001). As expected, stratification by IgA and IgG status revealed the longest median graft survival in IgA/IgG double negative patients (TtD 127 months). Patients tested positive exclusively for IgG Abs displayed intermediate graft survival (TtD 116 months) whereas, IgA/IgG double positive patients had a significantly reduced median graft survival compared to any other subgroup (TtD 88 months, p < 0.001). Only three patients showed exclusively IgA Abs and were not possible to analyze statistically. In our previous study with 694 patients, we showed, that the presence of donor specific IgA (IgA-DSA) Abs correlated with a significant worse outcome (TtD 76 months) compared to IgA positive patients without showing IgA-DSA (TtD 82 months). The presence of serum anti-HLA-IgA Abs in conjunction with IgG Abs marks a high risk subgroup in kidney Tx patients with a significantly reduced graft survival compared to patients displaying exclusively IgG Abs. This influence of IgA may indicate a novel functional contribution for improved risk stratification in the post and potentially pre transplantation monitoring.

HLA-specific antibodies detected by solid phase assays are increasingly used to define unacceptable HLA antigen mismatches (UAM) before renal transplantation. The accuracy of this approach is unclear. Day of transplant sera from 211 complement-dependent cytotoxicity crossmatch-negative patients were retrospectively analyzed for donor-specific anti-HLA antibodies (DSA) using Luminex technology. HLA were defined as UAM if DSA had mean fluorescence intensity above (I) 3000 (patients retransplanted and those with DSA against HLA class I and II) or 5000 (all other patients), (II) 5000 for HLA-A, -B, and -DR and 10 000 for HLA DQ or (III) 10 000 (all HLA). We then studied the accuracy of these algorithms to identify patients with antibody-mediated rejection (AMR) and graft loss. UAM were also determined in 256 transplant candidates and vPRA levels calculated. At transplantation, 67 of 211 patients had DSA. Of these, 31 (algorithm I), 24 (II) and 17 (III) had UAM. Nine (I and II) and 8 (III) of 11 early AMR episodes and 7 (I), 6 (II) and 5 (III) of 9 graft losses occurred in UAM-positive patients during 4.9 years of follow-up. Algorithms I and II identified patients with persistently lower glomerular filtration rate even in the absence of overt AMR. Of the waiting list patients, 22-33% had UAM with median virtual panel reactive antibody of 69.2% to 79.1%. Algorithms I and II had comparable efficacy but were superior to Algorithm III in identifying at-risk patients at an acceptable false-positive rate. However, Luminex-defined UAM significantly restrict the donor pool of affected patients, which might prolong waiting time.

Macrophages are key mediators of the therapeutic effects exerted by monoclonal antibodies, such as the anti-CD38 antibody MOR202, currently introduced in multiple myeloma (MM) therapy. Therefore, it is important to understand how antibody-mediated effector functions of myeloma-associated macrophages (MAMs) are regulated. Here, we focused on the effects of vitamin D, a known regulator of macrophage effector functions. Consequently, it was the aim of this study to assess whether modulation of the vitamin D pathway alters the tumoricidal activity of MAMs. Here, we demonstrate that MAMs display a defective vitamin D pathway with reduced expression level of CYP27B1 and limited tumoricidal activity which can be restored by the IMiD lenalidomide in vitro. Furthermore, our data indicate that the vitamin D pathway of MAMs from MM patients does recover during an IMiD-containing therapy shown by an improved MOR202-mediated cytotoxic activity of these MAMs against primary MM cells ex vivo. Here, the ex vivo cytotoxic activity could be further enhanced by vitamin D supplementation. These data suggest that vitamin D holds a key role for the effector functions of MAMs and that vitamin D supplementation in IMiD combination trials could further increase the therapeutic efficacy of anti-CD38 antibodies such as MOR202, which remains to be investigated in clinical studies.

Summary: We reported previously on the widespread occurrence of anti‐HLA alloantibodies of the IgA isotype (anti‐HLA IgA) in the sera of solid‐organ re‐transplantation (re‐tx) candidates (Arnold et al., ). Specifically focussing on kidney re‐tx patients, we now extended our earlier findings by examining the impact of the presence and donor specificity of anti‐HLA IgA on graft survival. We observed frequent concurrence of anti‐HLA IgA and anti‐HLA IgG in 27% of our multicenter collective of 694 kidney re‐tx patients. This subgroup displayed significantly reduced graft survival as evidenced by the median time to first dialysis after transplantation (TTD 77 months) compared to patients carrying either anti‐HLA IgG or IgA (TTD 102 and 94 months, respectively). In addition, donor specificity of anti‐HLA IgA had a significant negative impact on graft survival (TTD 74 months) in our study. Taken together, our data strongly indicate that presence of anti‐HLA IgA, in particular in conjunction with anti‐HLA‐IgG, in sera of kidney re‐tx patients is associated with negative transplantation outcome.

Background. Pre-transplant donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA) have been associated with antibody-mediated rejection (AMR) and early kidney allograft loss. Uncertainties remain regarding the general applicability of these findings and the optimal induction therapy in DSA-positive patients. Methods. Pre-transplant sera from 174 patients receiving a crossmatch-negative kidney transplant were retrospectively analysed for DSA using Luminex technology. DSA with mean-fluorescence intensity (MFI) values above 500 were considered positive. All recipients received basiliximab induction and tacrolimus-based maintenance immunosuppression. DSA were monitored post-transplantation in patients with pre-transplant DSA. Antibody results were correlated with the incidence of rejection and graft loss. Results. In total, 61/174 patients had pre-transplant DSA. We found a strong correlation between the presence of DSA against class I and II HLA and DSA MFI greater than 10 000. Both DSA patterns independently predicted an increased risk of early AMR (odds ratio 4.24 and 4.75, respectively, P < 0.05). The risk for AMR in patients with intermediate MFI (3000–10 000) gradually increased with increasing MFI but group sizes were too small to allow for final conclusions. The risk for AMR was comparable to nonsensitized patients in patients with only class I or II HLA-DSA or MFI below 3000. 5-year allograft survival was lowest in patients with simultaneous presence of class I and II HLA-DSA and MFI above 10 000 (45%) but was comparable between patients with only HLA class I or II or no DSA (90.0, 90.0 and 88.1%, respectively). AMR was the only independent predictor of graft loss. Undetectable DSA 14 days post-transplant predicted excellent long-term outcome. Conclusion. The favourable outcome in the majority of DSA-positive patients despite non-depleting antibody induction and the poor outcome in patients with class I and II HLA-DSA and high DSA strength call for a differentiated therapeutic approach in this patient population.