Investigation of the chemical nature of soluble anti-tumour factor made from lymph nodes or spleens of allergized allogeneic mice.

The 105,000 supernatant (made from the homogenized lymph nodes of C57 B1 mice allergized with BP8 tumour cells in Freund's complete adjuvant) was fractionated on a G-75 Sephadex column. The high molecular weight fraction, >70,000, protected C3H mice against fatal challenge with BP8 tumour cells. In pilot experiments using Sephadex G-200 the anti-tumour activity was in a molecular weight fraction slightly greater than the main protein peak. When supernatant was fractionated on G-200 with I-labelled mouse IgG as an internal marker the main anti-tumour activity coincided with the position of the IgG but there was some activity in fractions of higher molecular weight. Fractionation of serum from allergized C57 B1 mice gave a similar pattern of activity. Experiments using affinity chromatography demonstrated that the anti-tumour activity was removed by anti-Fab and by anti-IgM sera. The possibility that the anti-tumour activity of the 105,000 supernatant made from allergized lymph nodes is a 7s IgM is discussed.