Treatment of cancer using chimeric t cell receptor proteins having multiple specificities

A system comprising:

• a first chimeric membrane protein comprising an extracellular domain comprising a first antigen binding domain and a first extracellular domain derived from the extracellular domain of CD3 gamma, delta, or epsilon, a transmembrane domain, and an intracellular domain comprising a first intracellular co-stimulatory domain derived from a protein other than CD3 gamma, delta or epsilon;
• and
• a second chimeric membrane protein comprising an extracellular domain comprising a second antigen binding domain and a second extracellular domain derived from the extracellular domain of CD3 gamma, delta, or epsilon, a transmembrane domain, and, optionally, an intracellular domain comprising a second intracellular co-stimulatory domain derived from a protein other than CD3 gamma, delta or epsilon;
• wherein the first antigen binding domain and the second antigen binding domain are not identical, and wherein the first extracellular domain derived from the extracellular domain of CD3 gamma, delta, or epsilon and the second extracellular domain derived from the extracellular domain of CD3 gamma, delta, or epsilon are not identical.