D^d-ζ thymocytes show an increased percentage of DN cells expressing high levels of CD5. (A) Freshly isolated thymocytes from MHC-D^d (left column) or homozygous 130 D^d-ζ (right column) transgenic mice were evaluated by flow cytometry. The CD4^–CD8^–(DN) gated cells were examined for CD3 and CD5 expression. The percentage of viable gated cells is indicated in each quadrant. (B) Fresh thymocytes from panel A were gated on CD3^–CD5^high cells as indicated and evaluated for D^d, Thy1.1, CD25, CD44, or Ly-6C expression. MHC-D^d cells are represented with a thin solid line, D^d-ζ by a thick solid line, and control fluorochrome-labeled Ab by a dotted line.