CD300LD is a member of the CD300 family of proteins and is a single transmembrane protein specifically highly expressed in neutrophils and polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). It plays a significant role in tumor progression by regulating the recruitment of PMN-MDSCs and inhibiting T-cell infiltration through the STAT3-S100A8/A9 axis. Studies have shown that CD300LD knockout mice exhibit significantly inhibited tumor development, with reduced accumulation of PMN-MDSCs and increased numbers of immune effector cells such as CD4+ and CD8+ T cells and natural killer cells. This suggests that targeting CD300LD may remodel the tumor immune microenvironment from an immunosuppressive state to an activated state, offering potential for personalized targeted therapy. Additionally, CD300LD has been implicated in the regulation of interleukin-6 and tumor necrosis factor production, further highlighting its importance in immune responses.