The effects of gold sodium thiomalate on the binding and internalization of concanavalin A in human mononuclear phagocytes.

The effects of gold sodium thiomalate (GST) on the binding and internalization of concanavalin A (Con A) in human mononuclear phagocytes (M phi) were investigated in vitro. First, the binding and internalization of Con A were examined quantitatively using 3H-Con A. The prolonged incubation with GST induced a prominent inhibition of 3H-Con A internalization in M phi. The inhibition was increased in parallel with both increasing concentrations of GST and increasing time intervals of the incubation with GST. On the other hand, GST failed to significantly affect the binding of 3H-Con A to the M phi surface receptor. Second, the binding and internalization of Con A were examined qualitatively by fluorescein isothiocyanate-conjugated Con A (FITC-Con A). After incubation with GST for 72 h, the internalization of FITC-Con A was prominently impaired in vacuolated M phi. A significant inhibition of FITC-Con A internalization was not observed in either GST-treated nonvacuolated M phi or non-GST-treated M phi. Thus the inhibition of FITC-Con A internalization in GST-treated vacuolated M phi seemed to account for the inhibition of 3H-Con A internalization in all the GST-treated M phi populations. The binding of FITC-Con A to the cell surface receptor and the clustering of FITC-Con A receptor complexes were not detectably changed in any of the M phi populations. These results indicated that GST alters the initial step in the activation of M phi by Con A, namely the internalization of this mitogen.(ABSTRACT TRUNCATED AT 250 WORDS)