The lack of BTK in X-linked agammaglobulinemia (XLA) patients does not affect monocytes and polymorphonuclear cells (PMN) phenotype and functions. In this study, we show that XLA patients had an increased frequency of the intermediate monocytes subset and that BTK-deficient monocytes and PMN had a normal expression of receptors involved in the activation and cellular responses. We demonstrate that BTK is not required for migration, phagocytosis and the production of reactive oxygen species (ROS) following engagement of FC gamma receptors (FcγR). XLA monocytes and PMN showed an efficient calcium (Ca2+)-independent activation of oxidative burst, suggesting that oxidative burst is less dependent by Ca2+ mobilization. The phagocytosis was functional and it remained unaltered also after Ca2+ chelation, confirming the independence of phagocytosis on Ca2+ mobilization. Intravenous immunoglobulin (IVIg) infusion exerted an anti-inflammatory effect by reducing the frequency of pro-inflammatory monocytes. In monocytes, the IVIg reduce the oxidative burst and phagocytosis even if these functions remained efficient.

Ibrutinib is a tyrosine kinase inhibitor used in the treatment of a variety of lymphoid malignancies, including chronic lymphocytic leukemia (CLL). Drugs inhibiting B-cell-receptor (BCR)-associated kinases, including BTK inhibitors, act on B cells and on a wide spectrum of tissues and cells, including innate immunity cells. Thus, alterations in the Bruton's tyrosine kinase (BTK) kinase function could lead to an impairment of innate immune cells functions and to an increased infectious risk in patients receiving BTK inhibitors. We analyzed in vivo neutrophils oxidative burst, neutrophils granules release and cytokine production in relapsed/refractory CLL patients treated over time with ibrutinib as single-agent. We observed a dramatic reduction of neutrophils oxidative burst, Fc gamma receptors (FcγRs)-mediated degranulation and IL-8 plasma levels already after the first forty-eight hours of therapy with ibrutinib. However, ibrutinib treatment did not alter the surface expression of CD11b nor cytokine and proteinases release not mediated by FcγRs engagement. After three weeks, oxidative burst was still impaired, while degranulation and IL-8 levels were restored. In a group of CLL patients who survived for more than three years, all processes triggered by FcγRs completely recovered except the release of neutrophil elastase (NE) and IL-8. In conclusion, during the initial phases of ibrutinib therapy, the reduction of IL-8, NE, myeloperoxidase (MPO) levels and oxidative burst negatively impacted on mechanisms involved in neutrophils microbicidal activity.

No abstract

No abstract