MDK and neoplasm: However, their activity is often compromised by a variety of mechanisms,94 such as tumor-induced immune checkpoint activation, T cell exhaustion, and infiltration by Tregs.95 Additionally, tumor cells release immunosuppressive cytokines, including TGF-β, which inhibit T cell activity.96 Midkine, identified as a factor produced by NF1-mutated neurons, can activate T cells, particularly CD8+ T cells.