SOLID-PHASE INTERLEUKIN-2

Interleukin 2 was bound to Sepharose beads in order to assess its potential bioactivity in vitro. Although the cytokine was attached to the solid phase via a standard chemical reaction for covalent coupling, it was spontaneously released into culture medium in an active form during short-term incubation. Release was absolutely dependent on the availability of soluble protein in the incubation medium, and it was greater at 37 than at 4-degrees-C. Approximately 80% of the cytokine attached to the Sepharose beads was recovered in the medium after appropriate incubation for several days. The release of interleukin 2 from the solid phase resulted from the dissolution of aggregated cytokine. Noncovalent self-aggregation of interleukin 2 onto solid surfaces represents an unusual biochemical property that has implications for the molecular interactions of the cytokine with the solid phase, for the use of bound interleukin 2 in preparative or analytical modes, and for the development of immunotherapy for patients with solid tumors.