Relation between a spleen-derived immunosuppressive peptide and the immunoglobulin-binding factor

Isolated soluble fractions from spleen cell culture supernatants induce tumor enhancement

Supernatants of spleen cell culture from small-tumor-bearing mice, large-tumor-bearing mice, and large-tumor resected mice were fractionated by Sephadex G-100. The biological activity on tumor growth of all fractions was tested in vivo. It was found that only one fraction (MW: 220-250 kD) from spleen cell supernatants of small-tumor-bearing mice or large-tumor resected mice enhanced tumor growth. In spleen cell supernatants from large-tumor-bearing mice, two fractions had enhancing activity (MW: 220-250 and 100-10 kD). Thus, the surgical resection of large tumor induced disappearance of enhancing activity from the fraction of lower molecular weight.