CD4 and neoplasm: By conducting scRNA-seq analysis on paired samples of tumor primary and lymph node metastases, they discovered that the expression of genes controlling the expression of major histocompatibility complex (MHC) class II molecules were increased in tumor cells in lymph nodes, and the expression of costimulatory molecules was lacking, resulting in the decrease of CD4+ effector T cells and the increase of immunosuppressive Treg cells in lymph nodes.