Recombinant perchloric acid-soluble protein suppresses the immunoglobulin production of human-human hybridoma HB4C5 cells.

Because perchloric acid-soluble protein (PSP) has been conserved evolutionally in various species from Escherichia coli to humans, it may reflect an involvement in basic cellular regulation. However, the precise function of PSP is currently unknown. In this study, we examined the direct effect of PSP on the production of immunoglobulin (Ig) using human B, HB4C5, NAT-30, and U266 cells because it has been reported that subcutaneous administration of PSP affects rodent immune systems. Suppression of Ig productivity and decrement of the cell viability was recognized only in HB4C5 cells by the addition of PSP into the medium. On the other hand, PSP had no effect on Ig productivity and cell viability in NAT-30 and U266 cells. In addition, PSP was clearly incorporated by HB4C5 but not by the other cells. These results suggest that the Ig production suppressed by PSP, which has been previously reported to inhibit protein synthesis, contributed to the incorporation of PSP into the HB4C5 cells.