Enchancement of leukemogenesis in mice after prolonged administration of anti-interferon or normal rabbit globulin.

The prolonged adminstration of rabbit anti-mouse L cell interferon globulin had a marked potentiating effect on Rauscher Murine Leukemia Virus (MuLV-R) infection in BALB/c mice, as shown by spleen size. Normal rabbit globulin had a lesser, but still significant, augmenting effect on splenic enlargement. It was possible to discriminate quantitatively between the non-specific enhancement of splenomegaly in MuLV-R infected mice due to antigenic stimulation with normal rabbit globulin and the effects due to elimination of endogenous interferon by specific antibodies. The difference in the spleen-enlarging activity between the anti-interferon IgG and normal rabbit IgG was found to be maximal 3-4 weeks after infection when potent, diluted anti-interferon IgG (58 microgram protein per dose) was used. It would appear that the endogenous interferon, even prodcued in undetectable amounts, plays an essential role in controlling infection with an oncogenic virus.