Suppressive effect of 1-methyladenosine on the generation of chemiluminescence by mouse peritoneal macrophages stimulated with opsonized zymosan.

The preparation of an in vitro assay system for the immunosuppressive activities of modified nucleosides on macrophage (M phi) functions is described. Briefly, Listeria-elicited mouse peritoneal M phi s (Lm-M phi s) were treated with nucleosides in vitro for 18 hr at less than 1 mM concentration and chemiluminescence (CL) was measured after stimulation with opsonized zymosan. To confirm the usefulness of this assay (in vitro test), the immunosuppressive activities of 1-methyladenosine (m1 Ado) and adenosine (Ado) were determined by mouse Listeria infection (in vivo test), CL generation by M phi s obtained from the peritoneal cavity of nucleoside-treated mice (in vivo-in vitro test), and the in vitro test. The immunosuppressive activity of m1 Ado detected by the in vitro test was confirmed by the in vivo and the in vivo-in vitro tests. As for Ado, no immunosuppression was detected by the in vivo and the in vivo-in vitro tests through a potent suppressive effect was detected by the in vitro test. The ineffectiveness of Ado can be explained by the in vivo conversion of Ado to an inactive form. Thus, the proposed in vitro test seems to be useful, with the provision that the known in vivo metabolism is taken into consideration.