Chimeric receptor (CR)–redirected lymphocytes (T bodies) have great potential in the eradication of tumor cells. To extend this approach to target cells that do not express surface ligands to costimulatory receptors (eg, cancer cells), we have generated an antibody-based tripartite chimeric receptor (TPCR) that contains scFv linked to the costimulatory molecule, CD28 without its ligand-binding domain, and to the cytoplasmic moiety of the FcRγ subunit. In this study, we tested the ability of 2,4,6-trinitrophenyl (TNP)–specific TPCR to drive primary, naïve T cells derived from CR-transgenic (Tg) mice to undergo full activation. As a control, we used Tg mice expressing a similar transgene but lacking the signaling region of CD28 (Tg-TPCRΔCD28). Only T cells from the TPCR-Tg and not the CD28-truncated TPCR-Tg mice could undergo activation following stimulation on hapten-modified target cells not expressing B7. Moreover, when stimulated with TNP protein displayed on plastic, the TPCR-Tg T cells expressing the entire TPCR gene became fully activated for proliferation, interleukin 2 production, protection from apoptosis, and killing of TNP-modified target cells. Finally, TPCR-Tg mice manifested a delayed-type hypersensitivity response following skin challenge in the absence of priming. Taken together, our results suggest that the TPCR is the receptor configuration of choice for clinical applications using primary T or stem cells.