The CD4 Fluorophore Sampler Kit contains 18 different fluorophore formats of clone RPA-T4 with 10 tests of each antibody per vial.? It can be useful to have the same clone in multiple fluorophore formats to enable instrument characterization and standardization.CD4, also known as T4, is a 55 kD single-chain type I transmembrane glycoprotein expressed on most thymocytes, a subset of T cells, and monocytes/macrophages. CD4, a member of the Ig superfamily, recognizes antigens associated with MHC class II molecules, and participates in cell-cell interactions, thymic differentiation, and signal transduction. CD4 acts as a primary receptor for HIV, binding to HIV gp120. CD4 has also been shown to interact with IL-16.