Persistence of immunogenicity of antigen after uptake by macrophages

Peritoneal macrophages were cultured for several hours after uptake of (131)I-hemocyanin. The cells degraded most of the (131)I-labeled protein within 2-5 hr. Their ability to prime lymphocytes of syngeneic mice for a secondary immune challenge remained unchanged for long periods of time despite the loss of more than 90% of the original content of antigen. The persistence of immunogenicity was associated with a small percentage of antigen retained by the cell in a form which was protected from rapid breakdown and elimination.