FC 128NON-HLA ANTIBODIES AND EPLET MISMATCHES IN KIDNEY TRANSPLANT RECIPIENTS WITH A HISTOLOGICAL PICTURE OF ANTIBODY-MEDIATED REJECTION WITH AND WITHOUT HLA DONOR-SPECIFIC ANTIBODIES

Background and Aims

Correlation between antibody-mediated rejection (ABMR) and HLA donor-specific antibodies (DSA) is strong but imperfect in kidney transplant (KT) recipients, raising the possibility of other detrimental antibodies contributing to ABMR. The role of non-HLA antibodies on outcomes is not well known.

Method

We retrospectively assessed KT biopsies scored according to Banff’15 classification. Pre- and post-KT serum samples were checked for HLA and non-HLA antibodies (MICA-Ab, angiotensin II type 1 receptor (AT1R)-Ab, endothelin-1 type A receptor (ETAR)-Ab and crossmatches with primary aortic endothelial cells (EC-XM)). We also analyzed HLA epitope mismatches between donors and recipients.

Results

One-hundred eighteen patients with normal (n=19), ABMR histology (n=52) or IFTA (n=47) in their biopsy were studied. Graft survival was worse in ABMR patients (p=0.003). Pre-KT HLA-DSA were more frequent in ABMR cases (p=0.006). At biopsy, 73% ABMR patients had HLA-DSA (p<0.001). Pre-KT AT1R-Ab were more frequent in ABMR compared with IFTA and normal cases (p=0.003), without differences in other non-HLA antibodies. Fourteen patients with histological ABMR (27%) had no detectable HLA-DSA post-KT and only 3 had non-HLA Ab. However, these ABMR-DSA- cases showed similar biopsy changes and graft survival compared with ABMR-DSA+. Pre- or post-KT non-HLA antibodies other than AT1R-Ab were detected similarly in ABMR and in normal or IFTA cases. Both total class II and DRB1 epitope mismatches were associated with postransplant DSA and ABMR-DSA+. Multivariate analysis showed that both pre-KT HLA-DSA and AT1R-Ab (DSA: OR: 3.39 [1.20-9.59], p=0.021; AT1R-Ab: OR: 5.31 [1.75-16.10], p=0.003) were strong independent predictors of postransplant ABMR-DSA+ (Table 1).

Conclusion

Despite highly prevalent HLA-DSA before and after transplantation in KT with histological ABMR, 27% of cases did not show circulating HLA-DSA. Pre-KT AT1R-Ab associated with ABMR-DSA+, but not MICA-Ab, ETAR-Ab or EC-XM+. Any of them associated significantly with ABMR-DSA-. Epitope mismatch predicted both postransplant DRB-DSA and ABMR-DSA+. Detection of pre-KT HLA-DSA and/or AT1R-Ab, together with HLA epitope mismatch assessment, are valuable tools for better DSA and ABMR prediction in KT patients.

FC 129CHANGES IN PERIPHERAL NK CELLS IN KIDNEY TRANSPLANT RECIPIENTS WITH AND WITHOUT HLA DSA

Background and Aims

Antibody-mediated rejection (ABMR) is a frequent cause of renal allograft loss. There is increasing evidence of the role of Natural Killer (NK) cells in the establishment of ABMR damage. Our group described that patients with donor-specific antibodies (DSA) and ABMR present higher proportions of NKG2A+ NK cell subset in peripheral blood than those without HLA DSA or HLA antibodies.

Method

We selected 177 kidney transplant recipients (KT) with renal biopsies 2011-2017: 77 with ABMR (DSA+: 53, DSA-: 24) and 100 without ABMR (DSA+: 15, DSA-: 85). We assessed graft survival with a median time of follow-up since the renal biopsy of 53 months. In 138 KT we evaluated the peripheral blood NK cell immunophenotyping and its value as a prognostic biomarker.

Results

Graft survival was worse in ABMR-KT at the end of follow-up (p<0.001) independently of DSA detection (p=0.63). Regarding NK cell immunophenotyping, we observed a lower proportion and absolute NK cell count in ABMR+DSA+-KT and ABMR+DSA--KT compared with ABMR-DSA--KT (p=0.027, p=0.017). ABMR+DSA+-KT showed higher proportion of NKG2A+ NK cells compared with ABMR-DSA--KT (p=0.007). All ABMR+ patients, independently of DSA detection, presented lower absolute NKG2A- NK cell count in comparison with ABMR-DSA--KT (p=0.001, p=0.017). Finally, a proportion of NKG2A- <30% was associated with lower graft survival 36 months after graft biopsy with ABMR (p=0.067) (Figure).

Conclusion

Graft survival is worse in ABMR+ compared with ABMR- KT independently of DSA detection. Kidney transplant recipients with ABMR show reduced peripheral absolute numbers of NK cells and NKG2A- NK cells regardless of undetectable DSA. This NK cell phenotype associated with a worse medium-term graft survival in cases with ABMR.

S100A7: from mechanism to cancer therapy

Within the tumor, malignant and stromal cells support each other by secreting a wide variety of growth factors and cytokines, allowing tumor growth and disease progression. The identification and regulation of those key factors in this crosstalk has opened the opportunity to develop new therapeutic strategies that not only act on the tumor cells but also on the stroma. Among these factors, S100A7 protein has gained interest in the last years. With key roles in cell motility its expression correlates with increased tumor growth, angiogenesis and metastatic potential. This work aims to deepen in the role played by extracellular S100A7 in the tumor microenvironment, offering a new integrative insight of its mechanism of action on each cellular compartment (tumor, endothelial, immune and fibroblast). As a result, we demonstrate its implication in cell migration and invasion, and its important contribution to the formation of a proinflammatory and proangiogenic environment that favors tumor progression and metastasis. Furthermore, we define its possible role in the pre-metastatic niche formation. Considering the relevance of S100A7 in cancer progression, we have developed neutralizing monoclonal antibodies, reporting for the first time the proof of principle of this promising therapeutic strategy for cancer treatment.

Osteomyelitis Resulting From Chronic Filamentous Fungus Olecranon Bursitis

We describe a case of Phaeoacremonium olecranon osteomyelitis. The patient, initially felt to have traumatic olecranon bursitis, was found to have an indolent filamentous fungus cultured from the olecranon bursa. In retrospect, x-rays revealed bony erosion, which heightened the index of suspicion for infection in this particular case. Surgical bursal excision was performed and antifungal therapy was administered with clinical resolution. This case emphasizes that aspiration, synovial fluid analysis, and culture of bursal fluid is essential in excluding typical and atypical causes of chronic bursitis.