The invention provides an isolated or purified CD8+? T cell which comprises an antigen-specific T cell receptor and an exogenous nucleic acid encoding a microRNA-155 (miR-155) molecule, and methods of preparing the same. The invention also provides a pharmaceutical composition comprising the CD8+ T cell a carrier. Further provided is a method for treating or preventing a medical condition, such as cancer, by adoptively transferring to a mammal an amount of the CD8+? T cells effective to treat or prevent the medical condition.
