The present invention provides a lipid nano-particle containing the following components (a) to (c): (a) a nucleic acid encoding a chimeric antigen receptor (CAR) or an exogenous T cell receptor (TCR)； (b) a cationic lipid； and (c) a non-cationic lipid. The present invention also provides: a CAR-expressing or exogenous-TCR-expressing immunocyte produced by introducing the lipid nano-particle into a T cell in vivo or ex vivo； and a means for the in vivo or ex vivo treatment of diseases including cancer using the immunocyte.
