Crucial role of marginal zone macrophages and marginal zone metallophils in the clearance of lymphocytic choriomeningitis virus infection.

Macrophages play a key role in the immune defense against pathogens. They control early invasion by antigen-unspecific phagocytosis of pathogens and act as professional antigen-presenting cells to induce antigen-specific T cell responses. To investigate the involvement of particular subsets of the splenic macrophages in an antiviral immune response, we selectively depleted mice of splenic marginal zone macrophages (MZM) and marginal zone metallophils (MM) using the clodronate liposome depletion technique. MZM- and MM-depleted mice were not able to control an infection with lymphocytic choriomeningitis virus (LCMV). In these mice, LCMV spread from the spleen to peripheral organs at an early phase of infection. The virus-specific cytotoxic T lymphocyte (CTL) response was induced initially, yet was exhausted in parallel with the overwhelming virus replication. These findings suggest that MZM and MM play a crucial role in the early control of a LCMV infection by preventing immediate virus spread to peripheral organs, but are not essential for the induction of the LCMV-specific CTL response.