Isolation and characterization of sea star factor

Area of Science:

• Immunology
• Marine Biology
• Biochemistry

Background:

• Sea star factor (SSF) from Asterias forbesi celomocytes is known to inhibit immune responses.
• It also suppresses mitogenesis induced by concanavalin A, a common immune stimulant.

Purpose of the Study:

• To isolate and purify the protein responsible for SSF's biological activities.
• To characterize the purified protein and investigate its binding properties.

Main Methods:

• Isolation and purification of a basic protein from sea star celomocytes.
• Determination of molecular weight and subunit composition via reduction.
• Binding assays using spleen cells, concanavalin A, and labeled/unlabeled SSF.

Main Results:

• A basic protein with a molecular weight of approximately 38,000 daltons was isolated and purified.
• This protein was identified as the active component responsible for inhibiting immune responses and mitogenesis.
• Binding studies indicated that SSF binds to a site distinct from the concanavalin A binding site on spleen cells.

Conclusions:

• The purified protein, sea star factor, is a potent inhibitor of T-dependent immune responses and concanavalin A-induced mitogenesis.
• The data suggest a unique binding mechanism for SSF, separate from that of concanavalin A, implying a novel pathway for immune modulation.