ARG1 and lung cancer: Expecting that the frequency and number of MDSCs could distinguish between lung cancer patients and healthy controls, immunoglobulin-like transcript 3 (ILT3), which is expressed by MDSCs [43], and arginase-1 (Arg-1) mRNA [44], which is expressed by MDSCs, could also be used as surrogate markers for the frequency of MDSCs in PBMC and as attractive targets for immune intervention.