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The PI3Kδ-inhibitor Idelalisib is approved for the treatment of Non-Hodgkin lymphoma. However, its use has been decreased within the last years due to deleterious infections such as cytomegalovirus and pneumocystis jirovecii. Here, we have investigated the effect of Idelalisib on human monocyte-derived dendritic cells (DCs) as important players in the induction of immune responses. We found that Idelalisib-treated DCs displayed impaired T cell stimulatory function. PI3Kδ inhibition during differentiation resulted in decreased Interleukin-12, Interleukin-13 and TNFα production by DCs after lipopolysaccharide stimulation. Moreover, DCs showed decreased expression of the activation marker CD83 after Idelalisib treatment. Further, in line with this was the failure of Idelalisib-treated DCs to properly induce allogeneic T cells in a dose-dependent manner. Finally, activation of the NFκB pathway was also ablated in Idelalisib-treated DCs. Our results implicate that severe infectious complications may not only result from direct PI3Kδ-inhibition in T cells, but also from impaired DC function in Idelalisib-treated patients. Here, we provide new insight into the pathogenesis of Idelalisib-associated infectious complications. Our study may further provide a rationale for the use of Idelalisib as a novel therapeutic option in inflammatory diseases.

We present the case of a 62-year-old man treated with high-dose chemotherapy and consecutive autologous stem cell transplantation for mantle cell lymphoma, who developed high fever and a rash of the trunk and both axillae 10 days after stem cell transplantation.

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Sinusoidal obstruction syndrome (SOS) is a rare complication after allogeneic hematopoietic stem cell transplantation (alloHSCT) caused by endothelial dysfunction. Previous definitions and diagnostic criteria for the presence of SOS include bilirubinemia, hepatomegaly and weight gain, but histological evaluation is still the only way to prove the diagnosis of SOS. However, biopsy remains an invasive technique and is therefore undesirable in the alloHSCT scenario. Hence, a non-invasive diagnostic strategy is critical. Besides thorough clinical assessment and laboratory values, ultrasound examination remains part of the diagnostic workflow in clinical routine. Previous studies defined sonographic abnormalities, which are associated with the occurrence of SOS, but a standardized protocol to perform reliable abdominal ultrasound has not been finally defined. In this study, we evaluated a multi-parameter protocol including laboratory values as well as ultrasound examination pre- and post-alloHSCT. The application of this protocol was feasible in clinical practice and achieved a high inter- and intra-rater reliability. In our population, no case of SOS was identifiable and, in line with previous studies, no changes known to be associated with SOS were detected by ultrasound examination in our cohort. Additionally, we investigated subgroups of patients partly fulfilling SOS diagnostic criteria analyzing correlations between the fulfilled criteria and aberrances in ultrasound measurements pre- and post-alloHSCT. Although statistical examination may be limited by a small sample size and missing SOS cases, hyperbilirubinemia, thrombocytopenia and weight gain showed only a coincidence with selected, enlarged liver dimensions in few patients. This may underline the fact that hepatomegaly occurs as an unspecific finding after alloHSCT. Our protocol, including the ultrasound examination pre- and post-alloHSCT and laboratory parameters, may help to rule out SOS early, but validation in a greater population and different transplantation centers is required to warrant broader appliance. Nevertheless, we aim to contribute to an elaborate and standardized work-flow in peri-alloHSCT patient care.