As illustrated in Figure 1, the expression of LAG-3 in the TME has been observed on TILs [27], in particular CD4+ and CD8+ T cells [14,28], including regulatory T cells (Tregs) [29]; NKT cells [30]; B cells [31]; NK cells [32] as well as on plasmacytoid dendritic cells (pDCs) [33,34] and tumor-associated macrophages (TAMs) [35,36]. Here, LAG3 is linked to neoplasm.