Soluble interleukin-2 receptor: a useful prognostic factor for patients with hemophagocytic lymphohistiocytosis.

Elevation of serum concentrations of soluble interleukin-2 receptor (sIL-2R) has been shown in various hematolymphoid malignancies.'" Since its first documentation by Komp et alx in 1989, sIL2R has also been measured and tested for clinical usefulness as a prognostic indicator for patients with hemophagocytic lymphohistiocytosis (HLH)?"' However, these studies evaluated a small number of patients. In this study, we analyzed data on 74 HLH cases, including 71 children and 3 adults, that were collected over the past 10 years (Table 1). Diagnosis of all cases was compatible with the criteria of Henter et aI.l3 In the majority of cases, high serum concentration of ferritin (> 1,000 ng/mL) and/or high lactate dehydrogenase (> 1,000 I U L ) was shown. sIL-2R was determined by an enzyme immunoassay kit from T Cell Science (Cambridge, MA; normal values, < 1,090 U/mL for children and <860 U/mL for adults) and interferon (1FN)-y was assayed by Celltech Diagnostics (Birkshire, UK) SUCROSEP IFN-y immunoradiometric assay or human y-IFN RIA kit (Centcor Inc, Malvern, PA: values adjusted for Celltech, with normal values < 1 .0 U/mL). During the active phase of the disease, the serum concentrations of slL-2R ranged from 465 to 93,500 U/mL in these cases. Seventyone of the 74 cases displayed elevated values. Forty cases showed