The phenotype of TEC adherent thymocytes. Thymocytes (2.5 × 10⁷ in 1 mL FCS-free medium) from control, day 3, or day 4 P-Ir were added to 2BH4 subconfluent monolayers in 25-cm² flasks and incubated for 1 hour at 37°C. Nonadherent thymocytes were removed by aspiration followed by three gentle washes with warm medium. Adherent thymocytes were recovered in cold medium with FCS and stained for the markers shown on the axis. The circled region in the lower set of panels shows the percentage of CD8⁺ cells highly negative for CD4 labeling (ie, mature CD8 cells). Values were obtained with the labeling of pooled thymocytes from at least three mice per point.