TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method for delivering an agent to a tumor, involves administering a tumor-reactive T cell covalently bound to a nanoparticle, or a tumor-reactive T cell covalently bound to a maleimide-coated nanoparticle, where the nanoparticle comprises an agent which is released from the nanoparticle in vivo. Preferred Components: The cell is a T cell, B cell, natural killer (NK) cell, natural killer T (NKT) cell, tumor-reactive T cell, gut-specific T cell, skin-specific T cell, or hematopoietic progenitor cell. The cell is autologous to the subject, activated before administration to the subject, naturally occurring or genetically engineered. The subject requires hematopoietic reconstitution. The nanoparticle is 20-500 nm, preferably 100-300 nm, more preferably 150 nm in diameter. The nanoparticle comprises maleimide reactive groups on the surface or a lipid coating. The agent is an imaging agent, anticancer agent, interleukin or cytokine. The cytokine is interleukin (IL)-15/IL-15 receptor alpha . The agent is an antigen, preferably tumor antigen, adjuvant, drug, chemical compound, antibody or nucleic acid. The adjuvant is toll-like receptor (TLR) ligand. The nucleic acid is small interfering RNA (siRNA). The cell is covalently bound to several nanoparticles which comprise an identical agent or different agents. The nanoparticle is 100-10000, preferably 500, and more preferably 125-150. The method further involves binding the nanoparticle to the cell and providing the cell bound to the nanoparticle. The nanoparticle comprises DNA core. The nanoparticle further comprises lipid bilayer surface. The nanoparticle comprises poly(lactide-co-glycolide) (PLGA) core. The nanoparticle is in a lyophilized form. The tissue homing cell is a T cell, gut-homing T cell, or skin-homing T cell. The biodegradable nanoparticle is covalently bound to the tissue homing cell or is covalently conjugated to the surface of the hematopoietic progenitor cell. ACTIVITY - Cytostatic; Immunosuppressive; Antimicrobial; Antiarthritic; Antirheumatic; Antiinflammatory; Gastrointestinal-Gen.; Neuroprotective; Dermatological; Muscular-Gen.; Nephrotropic; Respiratory-Gen.; Antithyroid; Antibacterial; Hepatotropic; Virucide; Fungicide; Antiparasitic; Antimalarial. No biological data given.    MECHANISM OF ACTION - None given.    EXAMPLE - No suitable example given.