This disclosure relates to the genetic modification of DNMT3A gene in immune cells. In certain embodiments, the modified immune cells may be used in adoptive T cells therapies to enhance immune responses against cancer or chronic infections. In certain embodiments, the disclosure relates to deleting, changing, or inserting nucleotides within the DNMT3A gene in immune cells, e.g., human CD8 T cells, such that the DNMT3A gene product does not function for methylation. In certain embodiments, modification of the DNMT3A gene provides an improvement in antigen-specific T cells functions and/or an enhancement of the longevity of the cells.
