Final answer:
The synthesized glycoprotein with the added oligosaccharide may not match the recognition pattern of human immune cells, leading to them not recognizing the glycoprotein.
Step-by-step explanation:
The likely explanation for the immune cells not recognizing the synthesized glycoprotein is that the branched 14-sugar oligosaccharide added to GP1 is not the correct oligosaccharide for human immune cells recognition. Immune cells have specific receptors on their surface that recognize specific carbohydrate structures. If the added oligosaccharide does not match the recognition pattern of the immune cells, they will not be able to recognize and respond to the glycoprotein.