CD4 and cholangiocarcinoma: The administration of allogeneic Vδ2 γδ T cells to a metastatic CCA patient resulted in no adverse effects and was found to regulate peripheral immune cells, such as αβ T cells and NK cells, by increasing functional CD3+CD4+CD28+ helper T cells, CD3+CD8+CD28+ killer T cells, and CD3−CD56+ NK cells.