Effect of transgenic expression of human alpha 1-acid glycoprotein (AGP) on the glycosylation of human and mouse AGP in various transgenic mouse sera.

The occurrence and the glycosylation of human alpha 1-acid glycoprotein (AGP) was studied in two classes of transgenic mice expressing either the A, B and B' genes (ABB'-mice) or only the A gene of human AGP (A-mice). The glycosylation of the human AGP molecules in the transgenic mouse sera was compared with the glycosylation of mouse AGP in the same animal and with human AGP in normal human serum by studying their heterogeneity in binding to concanavalin A (Con A), using crossed affino immunoelectrophoresis (CAIE) with Con A as the affinocomponent in the first dimension gel. Three to four different glycosylated fractions of human as well as mouse AGP were revealed by this method in all the transgenic mouse sera. A close relationship was apparent between the heterogeneities in Con A binding of human and mouse AGP in the same transgenic mouse. The magnitude of this so-called Con A reactivity was, however, strongly dependent on the transgenic mouse studied. Especially within the group of ABB'-mice dramatic changes in Con A reactivity were found when the human AGP genes were expressed. This indicates in the first place that the oligosaccharide chains of the human AGP molecules expressed also mouse-specific features. Secondly, and more importantly, these findings indicate that the expression of the human AGP genes affected the glycosylation process of the transgenic mouse liver. This organ is the source of the AGP forms occurring in serum. We do not know whether this effect has been caused by the introduction or the expression of the human gene(s) or by the presence of human AGP in the Golgi system or in serum.(ABSTRACT TRUNCATED AT 250 WORDS)