Toll-Like-Receptor Expression and Cellular Immune Reconstitution In AML-Patients with Elevated Serum Ferritin Levels After Allogeneic transplant.

Abstract 1049

Elevated pretransplant serum ferritin levels have been associated with an increased susceptibility for opportunistic infections and increased incidence of morbidity and mortality after allogeneic haematopoietic stem cell transplantation (HCT). We studied in 81 patients who underwent myeloablative allogeneic HCT for acute myeloid leukemia pre- and posttransplant serum ferritin levels and correlated the serum ferritin levels with the TLR9 expression and the cellular immune reconstitution 3 and 12 months post transplant. Further, we studied in vitro-experiments in Kasumi-1 cells the TLR1, TLR2, TLR3, TLR5, TLR7, TLR9 and TLR10 expression after overwhelming iron and ferritin exposure. The average pretransplant serum ferritin level was 1245 μg/ml (mean) in all AML-patients (mean 1100μg/l for patients with AML in 1.CR and mean 1820μg/l for patients with AML > 1.CR). Post transplant serum ferritin level increased up to 2080 μg/ml (mean) for all AML patients (mean 1290mg/l for AML in 1.CR and mean 2350 μg/l for patients with AML > 1.CR). The application of 300ng iron to acute leukaemia cell lines SD1, and Kasumi-1 cells increased significantly TLR1, TLR2, TLR3, TLR5, TLR7 and TLR9 expression in relation to the housekeeping gene abl measured by real-time RT-PCR. In Kasumi-1 cells TLR1 increased up to 50,6% (p=0.014) TLR2 up to 35.5% (p=0.046), TLR3 up to 57,8% (p=0.006), TLR5 up to 62.9% (p=0.005), TLR7 up to 46.2% (p=0.02), TLR9 up to 44.2%(p=0.026) and TLR10 up to 54,7% (p=0.07) compared to untreated Kasumi-1 cells. The application of 2000μg/L ferritin increased TLR9 expression even more extensively in Kasumi-1 cells: TLR1 increased up to 332% (p<0.001), TLR2 up to 150% (p=0.016), TLR3 up to 293% (p<0.0001), TLR5 up to 349% (p<0.0001), TLR7 up to 287% (p<0.0001), TLR9 up to 229% (p=0.028). Elevated TLR-expression was also seen in CD34+ progenitor cells derived from volunteers.

Further, patients with elevated post transplant ferritin level > 2000 μg/l had an increased TLR9 expression in mononuclear cells (TLR9/ABL quotient 6485 versus 4543; p<0.05) 3 months post transplant. The numbers of T helper cells (mean 412 versus 231 cells/μl 3 months post transplant, p=0.014), and cytotoxic T cells CD4+CD8+ in patients with elevated serum ferritin level were significantly elevated after transplant (mean 285 versus 164 cells/μl 3 months post transplant, p=0.027), whereas no differences were found in the number of B19+ cells and Nk cells.

These results indicate that elevated ferritin levels might activate the innate immune system by increasing TLR expression. This might be of importance since we recently showed that increased TLR9 expression was associated with adverse impact on non-relapse mortality in the transplant setting. Further exaggerated TLR9 expression has been discussed to induce overwhelming immune responses as SIRS or ARDS. More studies are definitely necessary to evaluate the role of elevated iron overload on the innate immune system.