Inhibition of Epstein-Barr virus (EBV)-specific CD8(+) cytotoxic T lymphocyte (CTL) activity by soluble HLA class I in vitro

In the present study, the effects of soluble HLA (sHLA) class I molecules a gainst EBV-specific CTL were examined. Two different sources of sHLA class I, either bioengineered spliced form of HLA-B7 (sB7) or natural production from EBV-transformed B cells (natural sHLA), were added during the inductio n of CTL or incubated with MHC-restricted CD8(+) CTL, which were selected b y immunobeads just before testing for their cytotoxic activity. Both sB7 an d natural sHLA class I blocked the generation of CD8(+) CTL and also inhibi ted the cytotoxic activity of established CTL in a dose-dependent manner. I n both ways, natural sHLA class I was effective in 10-fold lower concentrat ions compared with sB7. The inhibitory effect did not require a sharing of the HLA allotypes between sHLA and the CTL. CTL, after being treated with s HLA, underwent apoptosis, which was considered here as the main mechanism.