[vibrio]

T cells kill infected cells by detecting foreign proteins using a lock and key tube mechanism (Key = foreign antigen, Lock = T cell receptor). Normally any given T cell an its off spring have only one specificity of lock (although collectively there are many millions of locks in the body). CAR-T therapy is when they pull out a bunch of T cells for a patient and genetically modify the cell to have a know lock which is specific for a key known to be on the Cancer, then put them back into the patient. So, relatively, there is a massive increase in the frequency of T cell with that specificity in the patient, and hopefully they kill the tumor cells.