Increase in the expression of human leukocyte antigen class I in human fibroblasts by soluble factors secreted from human cytomegalovirus-infected cells

The human cytomegalovirus (HCMV) is known to downregulate the expression of the human leukocyte antigen (HLA) class I for escape from immune surveilla nce, In order to understand the HCMF immune evasion mechanism, expression o f HLA class I on the surface of HCMV-infected cells was investigated A decr ease in the HLA class I expression was observed at higher MOI; whereas at a lower MOI a slight increase in the HLA class I expression was observed. Wh en HCMV-infected and uninfected cells were separately prepared on coverslip s and co-cultured, the increased BLA class T expression was observed in uni nfected eels. Treatment of the uninfected cells with the culture supernatan t from HCMV-infected cells resulted in an increase in the HLA class I expre ssion. A biochemical analysis of the HCMV-infected cell culture supernatant revealed the presence of interferon (IFN) beta, interleukin (IL)-I beta, a nd IL-6. The HLA class I-enhancing activity of the culture supernatant was mimicked by IFN beta, but not by IL1-beta or IL-6, and was partially revers ed by pretreatment with an antibody to IFN beta. Therefore, it appears that the HCMV infection of human foreskin fibroblast cells induces interferon b eta and other soluble factor(s) that are responsible for the up-regulation of the KLA class I expression.