BACTERIA-INDUCED NEO-BIOSYNTHESIS, STABILIZATION, AND SURFACE EXPRESSION OF FUNCTIONAL CLASS-I MOLECULES IN MOUSE DENDRITIC CELLS

Here, we show that bacteria induce de novo synthesis of both major his tocompatability complex (MHC) class I and II molecules in a mouse dend ritic cell culture system, The neo-biosynthesis of MHC class I molecul es is delayed as compared with that of MHC class II. Furthermore, bact eria stabilize MHC class I molecules by a 3-fold increase of their hal f-life. This has important consequences for the capacity of dendritic cells to present bacterial antigens in the draining lymph nodes. In ad dition, a model antigen, ovalbumin, expressed on the surface of recomb inant Streptococcus gordonii is processed and presented on MHC class I molecules. This presentation is 10(6) times more efficient than that of soluble OVA protein. This exogenous pathway of MHC class I presenta tion is transporter associated with antigen processing (TAP)-dependent , indicating that there is a transport from phagolysosome to cytosol i n dendritic cells. Thus, bacteria are shown to be a potentially useful mean for the correct delivery of exogenous antigens to be presented e fficiently on MHC class I molecules.