CD4 MicroBeads were developed for the isolation of CD4+ cells by direct magnetic labeling. CD4 is an accessory molecule in the recognition of MHC class II/peptide complexes by the TCR heterodimers on CD4+ T helper cells. CD4 is expressed on T helper cells and at a lower level on monocytes and dendritic cells. The CD4 molecule is the receptor for the human immunodeficiency virus. The CD4 antibody recognizes most thymocytes and about 65% of all peripheral blood T cells.