A positive difference in nature of envelopes of thymus- and uterus-derived leukemia viruses of AKR mice.

Thymus-derived leukemia virus of AKR/J mice was inactivated by anti-theta antiserum. But it was not inactiviated by the antiserum which had been absorbed with intact thymus cells of AKR/J or RF/J mice, and by anti-uterus-derived leukemia virus antiserum. In contrast, uterus-derived leukemia virus of the strain was not inactivated by anti-theta antiserum, but was neutralized by anti-uterus-derived leukemia virus antiserum. The results suggest the possibility that some constitutents of the envelope of thymus-derived leukemia virus are derived from the plasma membrane of thymus cells of AKR mice at the time of budding and that such constituents are not associated with the enveloped of uterus-derived leukemia virus.