Differential effects of parainfluenza virus type 3 on human monocytes and dendritic cells.

To understand the lack of protective immunity observed after infection with parainfluenza virus type 3 (PIV3), we tested the effect of the virus on human monocytes and monocyte-derived immature dendritic cells (DCs). Expression of viral antigens on the cell surfaces correlated with replication of the virus, which was marginal in monocytes but extremely efficient in DCs. The virus increased monocyte survival at least in part through the production of granulocyte-macrophage colony-stimulating factor but, in contrast, accelerated DC apoptosis.

IL-2-dependent HTLV-I-infected T cells escape from non-specific, MHC-unrestricted cellular cytotoxicity.

The susceptibility of NK cell-mediated cytolysis was compared between 5 human HTLV-I-transformed T cell lines and 10 newly established IL-2-dependent HTLV-I-infected lines. None of the cell lines were killed after 4 hr incubation with normal PBMC. However, after 20 hr, 3 HTLV-I-transformed lines were significantly lysed.