Acute infection of mice with lactate dehydrogenase-elevating virus enhances Fc and complement receptor activity of peritoneal macrophages.

Peritoneal macrophages isolated from Balb/c mice 1 day after infection with lactate dehydrogenase-elevating virus (LDV) exhibited a 5- to 10-fold enhancement of attachment and ingestion of sheep red blood cells coated with immunoglobulin (EAIgG) or immunoglobulin plus complement (EAIgMC). Macrophages isolated from mice 7 days after LDV infection or macrophages infected with LDV in culture were also slightly more active than macrophages from uninfected mice, but the differences were not significant. The results indicate that a specific increase in the number of Fc and C3 receptors on macrophages occurs during the acute phase of infection. This increase correlates with the transient appearance of interferon in acutely infected mice. We postulate that during the acute phase the productive infection of a subpopulation of macrophages that is permissive for LDV results in the synthesis of sufficient interferon to cause activation of the remaining non-permissive macrophages in the animal.