For example, exosomal glycoprotein A33, a type I membrane protein, originates only from colon epithelial cells, and may serve as an immunomarker for colorectal carcinoma (CRC) [13]; exosomal immune molecules, such as MHC molecules, originate from antigen presenting cells and are associated with specific immune responses [14]. Here, GPA33 is linked to colorectal carcinoma.