Conversely, the frequencies of potentially exhausted and immunosuppressive clusters: PD-1+GBlowCD45RO+CD8+ exhausted T cells (C1, p = 0.0458, S2 vs S3), Treg (C4, p = 0.0188, S1 vs S2), and PD-1+GBlowCD45RO+CD4+ exhausted memory T cells (C19, p = 0.0073, S2 vs S3) were significantly higher in S2 tumours than in either S1 or S3 (Fig. 2d). Here, CD4 is linked to neoplasm.