PDCD1 and Buschke-Ollendorff syndrome: Further, co-expression analysis of PD1 with the transcription factors Foxp3 or TOX indicated that PD-1pos lymphocytes (i.e., exhausted T cells) were reduced in RAS compared to BOS grafts (BOS vs. Ras: p = 0.003; Figures 3C, E and Supplementary Figure 7).