This unit describes the complete removal of T cells from lymphocyte preparations based on the presence of the glycoprotein Thy-1 on the cell surface of T lymphocytes. As in UNIT 3.3, cytotoxic elimination is employed; however, Thy-1-specific antibodies are used rather than MHC class II-specific antibodies so that T cells are eliminated rather than B cells and accessory cells. Murine T cells can be further fractionated into subpopulations based on their expression of cell differentiation markers CD4 (Leu3, L3T4, T4) and CD8 (Leu2, Lyt2,3). A protocol in this unit describes removal of T cell subsets by cytotoxic elimination using CD-specific antibodies. An alternate but technically more demanding method of enriching T cell subsets is the panning procedure described in UNIT 3.5.