Infection and expression of Toll-like receptors in lymphoid malignancy patients after autologous stem cell transplantation

Introduction
High-dose chemotherapy with autologous stem cell transplantation (ASCT) is one of the main strategies for the treatment of haematological neoplasms. Infections are the most common cause of morbidity and mortality from the ASCT procedure. However, it is challenging to predict when these complications are likely to arise. Toll-like receptors (TLRs) are present on various immune cells and play a broad role in immune surveillance. The aim of the study was to investigate the association between the expression of TLR genes and the occurrence of infections in patients treated with ASCT.

Material and methods
TLR expression was analysed in 60 patients who underwent ASCT. The median age was 54 years. Blood samples were taken before high-dose chemotherapy and at the time of haematopoietic recovery after ASCT.

Results
The expression of Toll-like receptor 4 (TLR4) was significantly higher in patients before ASCT than after transplantation. The expression of Toll-like receptor 9 (TLR9) was significantly higher in patients after ASCT than before transplantation. The expression of TLR9 and TLR4 at the start of the procedure was significantly lower in patients who went on to develop a bacterial infection after ASCT. Moreover, we also observed a significant positive correlation between the expression of TLR9 and neutrophil recovery time after ASCT.

Conclusions
Our findings suggest that TLRs could be useful biomarkers to predict and monitor infections in patients treated with ASCT.