CD45RA/CD62L/CD3/CD8

CD3 is a member of the immunoglobulin superfamily, which acts as a mediator of signal transduction, through association with the α/β or γ/δ T-cell receptor (TCR). Mammalian CD3 is a multimeric protein composed of four distinct polypeptide chains (ε, γ, δ, ζ), consisting of two heterodimers (εγ, εδ) and one homodimer (ζζ). CD3 is expressed by a high-percentage of circulating peripheral T-cells and is considered a pan T-cell marker. Clone UCHT1 specifically recognizes the 20kDa CD3ε chain. The CD8 antigen is expressed on the human suppressor/cytotoxic T-lymphocyte subset (CD3+CD8+), as well as on a subset of NK lymphocytes. The CD8 antigen is expressed on 19% to 48% of normal peripheral blood lymphocytes21 and the majority of normal thymocytes. CD45RA is an isoform of CD45, a member of the protein tyrosine phosphatase family, otherwise known as leucocyte common antigen (LCA), which acts as a positive regulator of T-cell co-activation, and is essential for the activation of T-cells through the antigen receptor. CD62L is present on 61% to 75% of normal human peripheral blood lymphocytes, 70% to 80% of E-rosetting cells, 10% of thymocytes, and most B lymphocytes. CD62L identifies regulatory subpopulations of T lymphocytes in both the CD8+ and CD4+ subsets. Approximately 75% of CD4+ T lymphocytes also bear the CD62L antigen. CD4+ CD62L– lymphocytes mediate the majority of helper functions involved in B-lymphocyte differentiation into plaque-forming cells, whereas the suppressor inducer functional subpopulation is included in the CD4+CD62L+ compartment. Approximately 60% of CD8+ T lymphocytes are recognized by CD62L. CD45RA is expressed by naïve T-cells, but not by activated and memory T-cells. CD45RA is an isoform of CD45, a member of the protein tyrosine phosphatase family, otherwise known as leucocyte common antigen (LCA), which acts as a positive regulator of T-cell co-activation, and is essential for the activation of T-cells through the antigen receptor. CD45RA is expressed by naïve T-cells and is down-regulated during activation.