Posttranslational modification of human T-cell growth factor.

Amino-terminal sequence analysis of human T-cell growth factor indicated that the amino acid in position 3 of the polypeptide chain was modified. Examination of the N-terminal octapeptide using the amino acid analyzer and mass spectrometry demonstrated that position 3 was a threonine which was linked to N-acetyl-D-galactosamine. This site of glycosylation is of practical significance since it appears to play a role in the selectivity of a monoclonal antibody for the factor.