CD8A and lung cancer: Immune checkpoint blockade increases the frequency of intratumoral CD39+ CD8+ T cells, and CD39 may serve as a surrogate marker of tumour-reactive CD8+ T cells in human lung cancer.28 We found that the frequency of CD39+ CD8+ T cells was significantly greater after neoadjuvant therapy than at baseline in patients who achieved pCR, while no significant differences were observed in the non-pCR group (Fig. 3l, m).