Incidence and role of antibody in graft injury: How can it best be monitored?

Anti-HLA donor-specific antibodies detected in positive B-cell crossmatches by Luminex predict late graft loss

The significance of B-cell crossmatching in kidney transplantation is controversial. Recipients (n = 471) transplanted in a single centre from 1987 to 2005 with complete T- and B-cell crossmatch records were studied. Sera from 83 patients transplanted across a positive B-cell crossmatch, with concomitant negative T-cell crossmatch (T-B+) on either current and/or peak sera were studied using Luminex to determine presence of donor-specific antibodies (DSA). Clinical outcomes of T-B+ patients were compared with 386 T-B- patients. T-B+ predicted vascular (p = 0.01), but not cellular (p = 0.82) or glomerular (p = 0.14) rejection. IgG HLA DSA were found in 33% (n = 27) of the T-B+ patients and were associated with higher risk of any (p = 0.047), vascular (p = 0.01) or glomerular (p < 0.001) rejection at 6 months. Of 27 patients with DSA, 18/21 (86%) were the complement-fixing IgG(1) and/or IgG(3) subclass antibodies. DSA imposed a statistically significant higher risk of graft loss 5 years posttransplant (1.8 [1.0-3.3], p = 0.045). This study showed that only one-third of positive B-cell crossmatch (BXM) was caused by DSA and was associated with late graft loss. Thus, using BXM to preclude kidney transplantation may potentially disadvantage >60% of patients in whom BXM is not indicative of the presence of DSA.

Kidney graft recipients with pretransplantation HLA CLASS I antibodies and high soluble CD30 are at high risk for graft loss

In the present study, we investigated whether pretransplantation HLA class I and class II antibodies and pretransplantation levels of soluble CD30 (sCD30) and IgA anti-Fab autoantibodies are predictive of kidney allograft survival. Pretransplantation sera of 504 deceased-donor kidney recipients were tested for IgG HLA class I and class II antibodies, sCD30, and IgA anti-Fab levels using the CTS 4 ELISA kit. Kidney graft survival was estimated by Kaplan-Meier method and multivariate Cox regression. Regardless of the presence of HLA class II antibodies, recipients with high HLA class I reactivity had lower 1-year graft survival than recipients with low reactivity (p < 0.01). Recipients with high sCD30 had lower 5-year graft survival rate than those with low sCD30 (p < 0.01). The sCD30 effect was observed in presensitized and nonsensitized recipients, demonstrated a synergistic effect with HLA class I antibodies (p < 0.001), and appeared to be neutralized in recipients with no HLA class II mismatches. IgA anti-Fab did not influence kidney graft survival. Our results indicate that high pretransplantation sCD30 levels and HLA class I positivity increase the risk of kidney graft loss regardless of other factors. Consequently, such determinations should be routinely performed to estimate recipients' risks of graft rejection before transplantation.

Humoral Theory of Transplantation: Mechanism, Prevention, and Treatment

We discuss the potential mechanisms of antibody-induced primary endothelium injury, which includes complement-dependent pathway (membrane attack complex formation, recruitment of inflammatory cells, and complement-complement receptor-mediated phagocytosis) and complement independent pathway antibody-dependent cell cytotoxicity. Secondary to endothelium injury, the following pathological reactions are found to be responsible for progressive tissue injury and final graft function loss: platelet activation and thrombosis, pathological smooth muscle and endothelial cell proliferation, and humoral and/or cellular infiltrate-mediated parenchyma damage after endothelium injury. We also introduce three categories of therapeutic strategy in the prevention and treatment of antibody-mediated rejection: (1) inhibition and depletion of antibody producing cells (immunosuppressants, antilymphocyte antibodies, splenectomy); (2) removal or blockage of preexisting or newly developed antibodies (immunoadsorption, plasmapheresis/plasma exchange, intravenous immunoglobulin); and (3) impediment or postponement of antibody-mediated primary and secondary tissue injury (anticoagulation, glucosteroids). In conclusion, because alloantibodies have destructive effect on allografts, alloantibody monitoring becomes extremely important. It will help clinicians to determine a patient's humoral responses against allograft and will therefore direct clinicians to optimize and/or minimize immunosuppressive drug therapy.