AbstractIt has been hypothesized that internalization and “processing” of the nominal antigen by antigen‐presenting cells may be a mandatory event in antigen handling prior to cell surface presentation of the immunologically relevant moiety to T lymphocytes. In previous functional and immunochemical analyses of macrophage (MΦ)‐associated nominal antigen, we obtained data strongly suggesting that an immunologically relevant pool of antigen was detectable on the surface of MΦ pulsed with a soluble protein antigen and then aged for 3–24 h. To provide further information about requisite events of MΦ antigen handling, we have attempted in this study to determine the origin of the nominal antigen associated with the surface of the pulsed‐aged cell using the terpolymerL‐glutamic acid,L‐lysine,L‐tyrosine (GLT) as the antigen. The surface‐bound GLT, after a 24‐h culture, appeared to be derived from GLT initially surface‐associated after the pulse. No evidence was obtained to support the notion that a significant quantity of GLT, initially internalized after the pulse exposure, was recompartmentalized to the cell surface. The turnover of cell‐surface GLT resembled the turnover of MΦ membrane proteins in general. These results, therefore, imply that the crucial events of MΦ antigen handling of GLT may entirel