Several examples of the effective use of atmospheric-pressure plasmas in selective interaction with cancer and normal cells are introduced and mechanisms of cell immune responses, e.g. due to the plasma affected redox balance are discussed. A featured example focuses on atmospheric-pressure plasma- and TRAIL-induced apoptosis in TRAIL-resistant colorectal cancer cells [PPAP, 2015, DOI: 10.1002/ppap.201400207]. The mechanisms of plasma anti-cancer treatments that can selectively kill cancer cells without harming normal cells are examined. Tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) is an example of a molecule that can selectively kill cancer cells but not normal cells. However, some tumors are resistant to the TRAIL treatment. Our group has demonstrated that atmospheric cold non-equilibrium gas plasmas (AGPs) selectively induced cell death in melanoma and colorectal cancer cell lines by activating TNF and caspases 3/7 apoptosis pathways. Interestingly, AGPs can be used to make TRAIL-resistant colorectal cancer cells sensitive to the TRAIL treatment. AGPs plus TRAIL synergistically promoted the induction of the death receptor 5 (DR5), thereby enhancing the activation and apoptosis of ROS-dependent caspases 3/7. Therefore, there is a strong indication of the specific mechanisms involved in AGP-assisted TRAIL-induced cancer cell death and the associated synergistic effects that AGPs has on TRAIL-resistant colorectal cancer cells. Other interesting examples of effective applications of atmospheric pressure plasmas for the effective control of intracellular responses are also presented.