Three forms of monocyte-derived neutrophil chemotactic factor (MDNCF) distinguished by different lengths of the amino-terminal sequence

Human monocyte-derived neutrophil chemotactic factor (MDNCF) was purified from culture supernatant of lipopolysaccharide-stimulated human peripheral blood mononuclear leukocytes on a column of Sepharose-bound murine monoclonal anti-MDNCF. About 65% of the culture fluid chemotactic activity was bound to the column. The unbound 35% probably represents chemotactic activity of other cytokines in the culture fluid. More than 85% of the bound activity was eluted by pH 2.5 glycine buffer. When this material was applied to an HPLC-CM column, gradient elution produced four well-separated A₂₈₀ peaks, each of which had chemotactic activity. N-terminal amino acid analysis of the four peaks revealed three different sequences. One (MDNCF-c) was identical to the sequence that we reported previously. The other two (MDNCF-a and -b) had seven and five additional amino acids, respectively, at the N-terminus. MDNCF-a, -b and -c accounted for 8, 47 and 45% of the total MDNCF peptide. Alignment with the MDNCF cDNA sequence shows that MDNCF-a results from cleavage of a 20 residue signal peptide. MDNCF-c results from culture fluid proteolytic cleavage of the N -terminal sequences of MDNCF-a and -b at an R-S bond. The three peptides occurred in the four HPLC-CM peaks in different ratios. The bulk of any one peptide was distributed in two adjacent HPLC-CM peaks. This suggests that each peptide exists in a minimum of two states. In contrast to our previous multi-step purification, the immunoaffinity and HPLC-CM column sequence resulted in complete purification of MDNCF in two steps and led to identification of two additional MDNCF peptides, one of which has not heretofore been detected.