Effects of severe burns on glycan microheterogeneity of four acute phase proteins

In serum from 8 severely burned patients, haptoglobin (Hp), alpha 1-acid glycoprotein (AG) and alpha 1-antitrypsin (AT) were found to be increased by factors of 5, 6 and 2 respectively. Ceruloplasmin (Cp) was slightly decreased. In order to appreciate possible modifications to the structure of their attached N-glycans, whole sera were fractionated on concanavalin A (Con A)-Sepharose and respective glycoproteins measured by laser nephelometry using a monospecific antiserum. In the serum from normal as well as burned patients Hp was almost entirely bound to the immobilized lectin (but eluted with 300 mmol/l alpha 1-methylglucoside) and Cp was bound at about 92%. For AG, in contrast, the fraction without affinity for Con A, 25% in normal serum, decreased to 5% in patients, whereas the retained species increased in proportion. A very weakly reactive fraction (which was only retarded and eluted without alpha-methylglucoside) amounted to 72% in both types of serum. When reduced and alkylated, this intermediate fraction gave rise to both non-retained and retained species always in a proportion of about 1/3. On the whole one concludes that there is a significant shift for AG in burned patients towards species enriched in bi-antennary (Con A-reactive) glycans. For AT a minor part was not recognized by the lectin and about 27% was retarded. The latter, which increased in burned patients, gave rise mainly to retained species after reduction and alkylation. This again suggests a shift to bi-antennary glycans.