L-selectin expression as a function of CD3 surface level in thymocytes obtained from control or irradiated mice. Numbers represent the percentages found for L-sel⁻ (left region), L-selⁱⁿ (middle region), and L-sel^hi (right region) thymocytes. The area tagged with “irrl” shows the labeling of control thymocytes with an irrelevant antibody. Values were obtained with the labeling of pooled thymocytes from at least three animals per point.