Marked and persistent eosinophilia in the absence of clinical manifestations

Abstract

Background: Although most patients with hypereosinophilic syndromes (HES) present with clinical signs and symptoms attributable to eosinophilic tissue infiltration, some untreated patients remain asymptomatic or have signs and symptoms, such as allergic rhinitis, for which the relationship to peripheral eosinophilia is unclear (hypereosinophilia of unknown significance [HEUS]).

Objective: To identify and characterize subjects with HEUS of 5 years duration or more as compared to untreated patients with symptomatic HES and healthy normal volunteers.

Methods: All subjects with eosinophilia underwent yearly evaluation, including a standardized clinical evaluation, whole blood flow cytometry to assess lymphocyte subsets and eosinophil activation, and serum collection. Peripheral blood mononuclear cells were cultured overnight with and without phorbol 12-myristate 13-acetate/ionomycin. Cytokines and chemokines were measured in serum and cell supernatants, and mRNA expression was assessed by using quantitative real-time PCR.

Results: Eight of the 210 subjects referred for the evaluation of eosinophilia (absolute eosinophil count [AEC] > 1500/μL) met the criteria for HEUS of 5 years duration or more (range, 7-29 years). Peak eosinophil count and surface expression of eosinophil activation markers were similar in subjects with HEUS and in untreated subjects with platelet-derived growth factor alpha-negative HES (n = 28). Aberrant or clonal T-cell populations were identified in 50% of the subjects with HEUS as compared to 29% of the subjects with HES (P = .12). Increased levels of IL-5, GM-CSF, IL-9, and IL-17A were also comparable in subjects with HEUS and HES. Serum levels of IgE and IL-13 were significantly increased only in subjects with HES.

Conclusions: A small number of patients with persistent peripheral eosinophilia (AEC > 1500/μL) appear to have clinically benign disease.

Keywords: Eosinophil; cytokine; hypereosinophilic syndrome; pathogenesis.

FIG 1

Serum IgE and TARC levels. A, Serum IgE levels in subjects with HE_US (n = 8) and untreated HES (n = 28). B, Serum TARC levels in subjects with HE_US (n = 8) and untreated HES (n = 24) and in normal controls (n = 20). Open circles are used to denote subjects with clonal and/or aberrant T-cell populations. GMs are indicated by horizontal bars. Serum IgE level of less than 150 IU/mL (Fig 1, A) and serum TARC level of 1000 pg/mL or less (Fig 1, B) are indicated by gray shading. C, Serum TARC levels over time in 6 subjects with HE_US. A TARC level of 1000 pg/mL is indicated by the horizontal dashed line. SUBJ, Subject

FIG 2

AEC and eosinophil activation over time. Open circles indicate the first documented AEC for an individual subject. The gray shading represents a normal AEC (<400/mm³), and the dashed lines represent the HES-defining AEC of 1500/µL. Eosinophil expression of HLA-DR, CD25, and CD69 at each time point is depicted in the boxes beneath each graph. Above-normal expression is indicated in black, normal in gray, and no data collected in white. SUBJ, Subject.

FIG 3

Eosinophil surface activation marker expression. The percentage of eosinophils expressing CD25, CD69, or HLA-DR is shown for subjects with HE_US (n = 8) or untreated HES (n = 26). Open circles are used to denote subjects with clonal and/or aberrant T-cell populations. GMs are indicated by horizontal bars, and the normal range is indicated by gray shading. P = not significant for all comparisons.

FIG 4

Serum cytokine and chemokine levels. Each box represents the value for a given cytokine for an individual subject with HE_US, untreated HES, and normal controls (NL). The color of the box reflects the serum level for the individual subject compared with levels of the same cytokine in all the other subjects, ranging from dark green (no measurable analyte) to dark red.

FIG 5

Cytokine and chemokine production by PBMCs. A, Levels of GM-CSF, IFN-γ, IL-5, IL-9, IL-10, IL-17A, IL-13, TNF-α and IL-2 in supernatants from PMA/ionomycin-stimulated PBMCs from subjects with HE_US (n = 6) and untreated HES (n = 6) and normal controls (n = 25). Values are represented as stimulated minus unstimulated cytokine levels measured in supernatants collected after 6 hours in culture. Each symbol represents data from an individual subject. The horizontal bar denotes the GM. Open circles represent subjects with a clonal and/or aberrant T-cell population. *P < .05, **P < .01, and ***P ≤ .001, Mann-Whitney test. B, Change in IL-8 levels in PBMC supernatants following PMA/ionomycin stimulation. *P < .05, ***P < .0001, Wilcoxon signed-rank test. NL, Normal; Stim, stimulated; Unstim, unstimulated.