Dysregulation of interleukin 5 expression in familial eosinophilia

Abstract

Background: Familial eosinophilia (FE) is a rare autosomal dominant inherited disorder characterized by the presence of lifelong peripheral eosinophilia (>1500/μL). Mapped to chromosome 5q31-q33, the genetic cause of FE is unknown, and prior studies have failed to demonstrate a primary abnormality in the eosinophil lineage.

Objective: The aim of this study was to identify the cells driving the eosinophilia in FE.

Methods: Microarray analysis and real-time PCR were used to examine transcriptional differences in peripheral blood mononuclear cells (PBMC), and in purified cell subsets from affected and unaffected family members belonging to a single large kindred. Cytokine levels in serum and PBMC culture supernatants were assessed by suspension array multiplexed immunoassays.

Results: Whereas IL-5 mRNA expression was significantly increased in freshly isolated PBMC from affected family members, this was not accompanied by increased mRNA expression of other Th2 cytokines (IL-4 or IL-13). Serum levels of IL-5 and IL-5 receptor α, but not IgE, were similarly increased in affected family members. Of note, IL-5 mRNA expression was significantly increased in purified CD3+ CD4+, CD14+, CD19+, and ILC2 cells from affected family members, as were IL-5 protein levels in supernatants from both stimulated PBMC and ILC2 cultures.

Conclusions: These data are consistent with the hypothesis that the eosinophilia in FE is secondary to dysregulation of IL-5 production in PBMC (and their component subsets).

Keywords: autosomal dominant; cytokine; eosinophil; hypereosinophilic syndrome; interleukin 5.

Conflict of interest statement

Conflict of Interest: None of the authors have a declared conflict of interest.

Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Figures

Figure 1

Gene expression analysis for chromosomal region [5q31.1 - 5q33.1]. (A) Results of ANOVA test for difference in geometric average expression. Probe sets with expression differences greater than 2–fold and (unadjusted) p-value

Figure 2

Cytokine mRNA expression by PBMC in FE. IL5, IL4, IL13 and IFNγ mRNA expression by unstimulated PBMC as assessed by qRT-PCR is shown as 1/ΔCt for affected (A) and unaffected (UA) family members and healthy controls (HC). Horizontal lines represent the geometric means for each group. **p<0.005 and ****p<0. 0001 as compared to affected family members.

Figure 3

Serum mediator levels in FE. Serum levels of IL-5, sIL-5Rα, IL-13, IgE, eotaxin1/CCL11, GM-CSF, TARC/CCL17 and IFN-γ are shown for individual affected (A) and unaffected (UA) family members. The horizontal lines represent the geometric means for each group. *p

Figure 4

Cytokine levels in supernatants from mitogen-stimulated PBMC in FE. Levels of IL-4, IL-5, and IL-13 in PMA/ionomycin stimulated PBMC supernatants are shown for individual affected (A) and unaffected (UA) family members. The horizontal lines represent the geometric means for each group.

Figure 5

IL5 mRNA expression by PBMC subsets in FE. IL5 mRNA expression by unstimulated PBMC subsets as assessed by qRT-PCR is shown as 1/ΔCt for individual affected (A) and unaffected (UA) family members. The horizontal lines represent the geometric means for each group. *p<0.05 as compared to affected family members.

Figure 6

ILC subset frequency and net IL-5 production in FE. A) Percentage distribution of ILC1, ILC2 and ILC3 subsets are shown for individual healthy controls (HC) and affected (A) family members. B) Net IL-5 release from unstimulated and PMA/Ionomycin stimulated, flow-sorted ILC2 subsets. Horizontal lines represent the geometric means for each group. *p