Figure 4.

CD4⁺CD8⁻ thymocytes are more potent than CD4⁺ CD45RC⁻ cells at preventing development of thyroiditis in TxX PVG rats. PVG rats were thymectomized at 3 wk of age and given four equal doses of 275-rad ¹³⁷Cs γ-irradiation at 2-wk intervals starting 1 wk after thymectomy. CD4⁺CD8⁻ thymocytes were purified from thymus of 6-wk-old PVG rats by depletion of CD8⁺ cells, and CD4⁺CD45RC⁻ cells were purified from TDLs of 12-wk-old PVG rats by depletion of CD8⁺ and CD45RC⁺ cells. Shortly after their last irradiation, groups of rats were reconstituted either with CD4⁺CD8⁻ thymocytes at doses of 10⁵, 5 × 10⁵, 10⁶, 5 × 10⁶, or 10⁷ per rat, or with CD4⁺CD45RC⁻ cells at doses of 10⁶, 5 × 10⁶, or 10⁷ per rat. Development of anti-Tg antibodies was determined between 4 and 12 wk after the final irradiation by specific ELISA. Data are expressed as percentage of rats protected from development of disease, where the incidence of protection in the control group (42 out of 125 control rats failed to develop disease) is considered 0% protection. NP, no protection. Statistics versus controls: ^a P > 0.11; ^b P < 0.0046; ^c P < 1.6 × 10⁻⁷; ^d P < 2.3 × 10⁻⁶; ^e P < 1.8 × 10⁻⁵; ^f P > 0.4; ^g P < 8 × 10⁻⁹; ^h P < 7 × 10⁻⁸.