X-linked lymphoproliferative syndrome (XLP) is a rare primary immunodeficiency characterized by increased vulnerability to Epstein-Barr virus infection. XLP type 1 is caused by mutations in SH2D1A, whereas X-linked inhibitor of apoptosis (XIAP) encoded by XIAP/BIRC4 is mutated in XLP type 2. In XIAP deficiency, hemophagocytic lymphohistiocytosis (HLH) occurs more frequently and recurrence is common. However, the underlying mechanisms remain mostly unknown. We describe the characteristics of the cytokine profiles of serum samples from 10 XIAP-deficient patients. The concentration of interleukin (IL)-18 was strikingly elevated in the patients presented with HLH, and remained high after the recovery from HLH although levels of other pro-inflammatory cytokines approached the normal range. Longitudinal examination of two patients demonstrated marked exacerbation of IL-18 levels during every occasion of HLH. These findings may suggest the association between HLH susceptibility and high serum IL-18 levels in XIAP deficiency.
Keywords: AOSD; ATP; EBV; Epstein–Barr virus; FHL; HLH; Hemophagocytic lymphohistiocytosis (HLH); Interleukin-18; LPS; NK; NOD2; PBMCs; SAP; SLAM; SLAM-associated protein; X-linked inhibitor of apoptosis; X-linked inhibitor of apoptosis (XIAP); X-linked lymphoproliferative syndrome; X-linked lymphoproliferative syndrome (XLP); XIAP; XLP; adenosine triphosphate; adult-onset Still’s disease; familial hemophagocytic lymphohistiocytosis; hemophagocytic lymphohistiocytosis; lipopolysaccharide; natural killer; nucleotide-binding and oligomerization domain 2; peripheral blood mononuclear cells; sJIA; signaling lymphocyte activation molecule; systemic juvenile idiopathic arthritis.
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