Isolation and characterization of immunopeptide from dialyzable leukocyte extract

The dialyzable leukocyte extract was fractionated using high-pressure liquid chromatography through an anion exchange column (preparative). Twenty-one fractions were obtained. Fraction 1, which gave maximum enhancement of E rosettes, was further purified by thin-layer chromatography on silica gel plates. Five ninhydrin-positive bands were seen. The area under each band was scraped from the plates and eluted. The fastest moving component was labeled S1 and the slowest moving S5. Fraction S3 had given maximum enhancement of E rosettes and was designated as immunopeptide. The immunopeptide was further characterized. It contained protein, ribose, and hexose. The molecular weight was determined to be 1870 by sedimentation equilibrium method. It contained 15 amino acid residues. The immunopeptide enhanced E-rosette formation in vivo when given in doses of 5 units/m², to four individuals with low E rosettes.