LANGERHANS CELLS ARE SUSCEPTIBLE TO MEASLES-VIRUS INFECTION AND ACTIVELY SUPPRESS T-CELL PROLIFERATION

We have previously reported that the measles virus (MV) could producti vely infect human dendritic cells (DC), derived in vitro from CD34(+) cord blood progenitors in the presence of GM-CSF and TNF-alpha, In thi s study, we provide evidence that freshly isolated Langerhans cells (L C), which are immature dendritic cells located in skin and mucosal epi thelia, are susceptible to MV infection in vitro as assessed by viral antigen expression by both LC syncytia and LC remaining as single cell s. Moreover, MV-infected LC completely block naive allogeneic CD4(+) T cell proliferation in response to uninfected LC, This active inhibito ry effect is not due to virus transmission from infected LC, is indepe ndent of the maturation stage of LC at the time of infection and is an tigen non-specific and MHC-unrestricted, Thus, both immature and matur e LC are susceptible to measles virus infection, which turns these eff icient antigen-presenting cells into active tolerogenic cells. LC infe ction may explain the long lasting immune suppression observed during natural measles infection.