CD8A and lymphopenia: Although vanadyl sulfate significantly increased the number of CD3− CD8− NK1.1+ cells in circulation, if NDV was included in the treatment regimen there was a dramatic reduction in the number of NK cells in the blood, likely due to the well-recognized phenomenon of virus-induced lymphopenia.57, 58, 59 It is plausible that intratumoral administration of NDV led to increased NK cell trafficking to the TME, and, as such, their numbers in circulation were reduced.