MUC1 and neoplasm: Tumour associated antigens (TAA) such as gp100 or MUC1, that are tissue- but not tumour-, specific were originally attractive targets due to the broad therapeutic usage across patients, but central tolerance to these antigens limits the efficacy of these vaccines as only T cells with low antigen avidity may be available for activation; however, evidence suggests that even some of these TAAs such as MUC1 may be differentially glycosylated between normal and tumour tissue, suggesting potential therapeutic benefit if targeted [60].