What are the similarities between CD4 cells and CD 8 cells?

CD4 and CD8 cells are two types of T lymphocytes that are present in the blood and play key roles in triggering cell-mediated immune responses. Both types of cells feature T cell receptor (TCR) variations, which help to identify the type of T cells. Both, CD4 cells and CD8 cells are differentiated from the common lymphoid progenitor cells in the bone marrow and go on to mature in the thymus.