CD4 and immune system disorder: Under in vitro setting, blockade of CCR4 revealed promising data by showing its potential to reverse various levels of immune dysfunction in both CD4 and CD8 T cells that we have discussed in the following points.T cell proliferation: T cell proliferation is a critical step for the clonal expansion of antigen-specific T cells and their further transition into effector cells, which is a fundamental requirement to mount an effective T cell response [30].