Retrovirus-induced immunosuppression via blocking of dendritic cell migration and down-regulation of adhesion molecules.

Dendritic cells (DC) within tissues may acquire and process antigens, carry them into lymph nodes and cluster and activate T cells. The ability of DC to acquire antigen and to migrate to lymph nodes was estimated during murine retroviral infection caused by Rauscher leukaemia virus (RLV). A novel mechanism of inducing immunodeficiency has now been identified. In mice infected with RLV, DC failed to migrate into lymph nodes following exposure of the skin to the contact sensitizer, fluorescein isothiocyanate. RLV infection of a proportion of DC both in skin and lymph nodes, shown by semi-quantitative polymerase chain reaction (PCR) and down-regulation of expression of adhesion molecules (CD54 and CD44) on the surface of Langerhans' cells, may contribute to the described phenomenon. A failure of DC migration could be an important immunosuppressive mechanism of RLV infection in mice and we speculate on a similar role for DC in human immunodeficiency virus-1 (HIV-1) infection in humans.