Alterations of Tamm-Horsfall protein immunoreactivity after partial desialylation and deglycosylation.

The role of the carbohydrate moiety of Tamm-Horsfall protein (THP) was investigated by studying the effect of partial enzymatic desialylation and deglycosylation on its immunoreactivity. In our experiments primarily sialic acid alpha 2,6 linked to a galactose was split off, resulting in a 14% increase of immunoreactivity. It was increased up to 21% by further removal of the sugar residues. We also found that complexes composed of THP and human serum albumin, immunoglobulin G or transferrin reacted with anti-THP antibodies. When these complexes were formed with desialylated or deglycosylated THP an essential increase of this reactivity (about 25%) occurred. Our studies indicate that modifications of the carbohydrate moiety of THP (which might occur in vivo by changes in the glycosylation process e.g. in pathologic conditions) lead to increased exposure of THP to the immune system.