CD3: UCHT1 antibody reacts with a combinatorial epitope of CD3epsilon, a 20 kD chain of the CD3/T-cell receptor (TCR) complex found on all mature T lymphocytes, NK-T cells and some thymocytes.CD4: RPA-T4 antibody reacts with CD4, a 55 kD single-chain type I transmembrane glycoprotein expressed on most thymocytes, a subset of T cells, and monocytes/macrophages.CD8: RPA-T8 antibody reacts with CD8a, a 32-34 kD type I glycoprotein. CD8a forms a heterodimer or homodimer with CD8b. CD8 also known as T8 and Leu2, is a member of the immunoglobulin superfamily found on the majority of thymocytes, a subset of peripheral blood T cells, and NK cells (express almost exclusively CD8a homodimers).