Involvement of Fas^hi thymocytes in the proliferative response to peptides from the AChR in three MG patients. (A) CD8-depleted thymocytes were labeled with anti-Fas (left). CD8-depleted thymocytes undergoing an additional depletion in Fas^hi cells were similarly labeled; about 90% of total Fas^hi cells were depleted (right). (B) After a 6-day period culture in the absence or in the presence of peptides from the AChR (1H and/or 3H, 5 μg/mL) the incorporation of ³H-thymidine (1 μCi for 0.2 × 10⁶ cells during 20 hours) was analyzed and is expressed in counts per minute (means ± SEM from 4 to 8 determinations). When Fas^hi cells were depleted, the spontaneous proliferation of CD8-depleted cells was abrogated and the proliferative response to AChR peptides is abolished.