CD4 and melanoma: Since it was previously observed that SSX4 was expressed in ~20% of malignant melanomas in a report by Türeci et al. [76], Ayyoub and colleagues also evaluated the presence of CD4+ T cells specific to this antigen in melanoma patients by stimulating CD4+ T cells isolated from the PBMCs of four melanoma patients with overlapping peptides derived from the amino acid sequence of SSX4 in the presence of APCs [115].