Abstract: A method of decreasing cytokine production and release is disclosed. In one embodiment, the method comprises the step of providing cytotoxic cells to a subject wherein the cells are preferably natural killer cells or T lymphocytes and are genetically modified to express a chimeric antigen receptor comprising a first element that is an extracellular antigen receptor and a second intracellular element that is a signaling moiety comprising altered ADAP-dependent or Fyn-dependent signaling such that downstream signaling causing cytokine release is decreased. Specific modifications of CD137 and NKG2D cytoplasmic tails are described. Additionally, methods to develop and screen drug compounds capable of compromising the binding between ADAP and Fyn and disrupting the downstream release of cytokines are described.