CD4 and head and neck squamous cell carcinoma: Compared with the normal tissues, the expression of HLA-DPA1 was increased significantly in the CD4 + T Conv cells, while receptor CD4 was also increased significantly in the pDC cells (Fig. 11A), explaining the reason for the construction of the MHC-II pathway between CD4 + T Conv cells and pDC cells in the tissues from HNSCC.