Cold plasma has become a promising application in the fields of biology and medicine. Its anti-microbial effects and stimulating properties on eukaryotic cells make plasma an encouraging option in treatment of chronic wounds. Apart from fibroblasts or keratinocytes, immune cells have a major contribution in wound healing. In this study, human peripheral blood mononuclear cells (PBMC) were tested for viability and proliferation after treatment with an atmospheric pressure argon plasma jet. In a treatment time dependent manner compromised viability of PBMC and proliferation of T cells could be shown and was assigned to induced apoptosis. Negligible cell damage was observed after short plasma exposure. Finally, plasma did not cause loss of function and treated but viable T cells retained the ability to proliferate.