Effect of anti‐mouse type‐1 interferon globulin on the evolution of moloney sarcoma virus induced disease in mice

The prolonged administration of potent sheep anti‐mouse type‐1 interferon globulin (anti‐IF IgG) had a marked potentiating effect on Moloney sarcoma virus (MSV) infection in mice. The extent of resistance to the MSV‐induced disease was age‐related. In 4‐week‐old BALB/c mice, anti‐IF IgG consistently induced 70–80% mortality due to the progression of early or late tumours and erythro‐leukaemia, whereas mortality of control mice was significantly lower. The same effect was obtained in 1‐year‐old BALB/c mice. However, in 4‐week‐old C57BL/6 or 6‐week‐old BALB/c mice, anti‐IF IgG enhanced only the growth of early tumours but had no effect on their regression. Antigenic stimulation with normal sheep globulin suppressed the growth of early tumours in suckling BALB/c or C57BL/6 mice and enhanced the evolution of late MSV‐induced disease in older mice.