The hypereosinophilia and high immunoglobulin E levels might partly be explained by elevated IL-5 and -13 as a result of lack of negative feedback from defective STAT3 signaling.
The identification of populations of aberrant T-lymphocytes secreting eosinophilopoietic cytokines such as interleukin-5 establish a pathophysiologic basis for cases of lymphocyte-mediated hypereosinophilia.
Indeed, imatinib mesylate has become first-line therapy for patients in whom the FIP1L1-PDGFRalpha fusion gene is detected, whereas corticosteroids remain the mainstay for management of patients in whom hypereosinophilia is secondary to the overproduction of interleukin 5 by abnormal T-cells.
Both AKO and DKO mice exhibited intrinsic hypereosinophilia and several-fold increase in levels of IL-5 and IL-13, and lowering of IFN-gamma to IL-4 ratio in the lungs, suggesting a Th2 bias of immune response.
An elevated serum tryptase level was observed in FIP1L1-PDGFRA-positive patients responding to imatinib, whereas serum IL-5 levels were not elevated in T-cell associated hypereosinophilia.
Since it has been known for some years that the genes encoding for GM-CSF, IL-3 and IL-5 reside on the long arm of chromosome 5, it could be possible that the chromosomal translocation in our patient resulted in excess production of these cytokines, hence causing the hypereosinophilia.
In situ hybridization of interleukin-2 (IL-2) and interleukin-5 (IL-5) cDNA probes on tissue sections identified the synthesis of IL-5 by the eosinophils, suggesting an autocrine pathway of eosinophilopoiesis leading to hypereosinophilia in this patient.
Constitutive production of the interleukins IL-5 and IL-6 by the lymphoma cell line OCI-Ly 17 derived from a patient with malignant lymphoma and hypereosinophilia.