Rebound eosinophilia after treatment of hypereosinophilic syndrome and eosinophilic gastroenteritis with monoclonal anti–IL-5 antibody SCH55700

Rebound eosinophilia after anti–IL-5 treatment. Each line shows an individual patient's changes in eosinophil counts. The dates plotted on the x-axis are not linear to show better the changes in eosinophil count observed during the early time points after treatment. Open symbols, patients with HES; solid, patients with EGE. ∗, †, 2 nonresponding patients, patients 3 and 4.

Normal control and patient pretreatment in vitro eosinophil survival. Eosinophil survival was assessed in media (A) or in the presence of IL-5 (B) for patients and controls. Results are expressed as the geometric mean values for triplicate cultures for each donor. Each symbol represents 1 individual. ^∗Patients with the FIP1L1/PDGFRA fusion.

In vitro eosinophil survival responses before and after treatment with anti–IL-5. Eosinophil survival was assessed before and at 1 month posttreatment in media (A) and in the presence of IL-5 (B). Results are expressed as the geometric mean values for triplicate cultures for each donor. Pretreatment and posttreatment responses are indicated by gray and black bars, respectively.

Prolongation of normal eosinophil survival by posttreatment patients' sera. Normal eosinophils were incubated with 1% sera from patients with HES (open symbols) or EGE (solid symbols) before and at 1 month posttreatment, and survival was assessed by flow cytometry. The horizontal bars are the median values. P=.01, Wilcoxon signed-rank test.

Reversal of the prolongation of normal eosinophil survival by posttreatment serum by the rat monoclonal antihuman IL-5 antibody TRFK5. Eosinophil survival was assessed in the presence of 1% posttreatment serum from a patient with HES and increasing concentrations of TRFK5 or rat IgG1κ isotype control antibody (B). Similar data are shown using a fixed concentration of recombinant IL-5 to prolong survival (A).

Changes in serum IL-5 levels. Serum IL-5 levels are compared before and at 2 to 3 days posttreatment (A) and at 2 to 3 days and 1 month posttreatment (B) for 6 patients with HES (open) or EGE (solid). ∗, †, 2 nonresponding patients. P=.04 for comparison between 2-day to 3-day posttreatment and 1-month posttreatment serum IL-5 levels.