PD-1 is expressed on a subset of CD4-CD8-thymocytes, and on activated T and B cells. PD-1 is thought to be involved in lymphocyte clonal selection and peripheral tolerance. The PD-1 ligands, PD-L1 (also known as B7-H1) and PD-L2 (B7-DC), are members of the B7 immunoglobulin superfamily. PD-1 is transiently expressed on CD4 and CD8 thymocytes as well as activated T and B-lymphocytes and myeloid cells. Additionally, Pdcd1mRNA is expressed in developing B-lymphocytes during the pro-B-cell stage. The RMP1-14 antibody has been reported to block the binding of PD-1 to its ligands (B7-H1 and B7-DC) and to inhibit T cell proliferation and cytokine production co-stimulated by macrophages (but not by dendritic cells and B cells) . Primary antibodies are available purified, or with a selection of fluorescent CF® Dyes and other labels. CF® Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF®405S and CF®405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.