A Major Role of Macrophage Activation by Interferon-Gamma During Mouse Hepatitis Virus Type 3 Infection: II. Age-Dependent Resistance

In contrast to adult mice, young AJ/mice, developed an acute hepatitis following infection with Mouse Hepatitis virus type 3. 100 % of the young animals died 4 to 5 days after the infection and high levels of virus were found in the liver and peritoneal exudate. Very low levels of IFN-$#x03B3; were found in the serum and peritoneal exudate of infected young mice. This was in contrast to the levels observed in adult mice. Spleen cells and macrophage cultures from young A/J mice, again in contrast to adult A/J mice, were shown to be unable to synthesize IFN-$#x03B3; and IFN-α/β respectively. Macrophages from either young or adult A/J mice were able to be activated with exogenous recombinant IFN-$#x03B3; or IFN-α/β, enabling both sets of cells to restrict MHV3 replication. The results indicate that the ability of the immune system to synthesize IFN-$#x03B3; and IFN-α/β may playa major role in the age-dependent resistance of A/J mice to MHV3.