Serum concentrations of IL‐5, GM‐CSF, and IL‐3 and the production by lymphocytes in various eosinophilia

The concentrations of interleukin‐5 (IL‐5), granulocyte‐macrophage colony‐stimulating factor GM‐CSF, and interleukin‐3 (IL‐3) in serum and in IL‐2‐stimulated lymphocyte culture medium (L‐IL2‐CM) prepared from patients with reactive eosinophilia were measured by enzyme‐linked immunosorbent assay (ELISA). Serum IL‐5 levels were increased in 16 out of 42 cases. GM‐CSF and IL‐3 were below the detectable levels in all sera examined. The concentrations of IL‐5 and GM‐CSF in L‐IL2‐CM were increased in 10 out of 29 patients. IL‐3 was below the detectable levels in all L‐IL2‐CM.