ANTIGEN-SPECIFIC DEVELOPMENT OF PRIMARY AND MEMORY T-CELLS IN-VIVO

The expansion and contraction of specific helper T cells in the draini ng lymph nodes of normal mice after injection with antigen was followe d. T cell receptors from purified primary and memory responder cells h ad highly restricted junctional regions, indicating antigen-driven sel ection. Selection for homogeneity in the length of the third complemen tarity-determining region (CDR3) occurs before selection for some of t he characteristic amino acids, indicating the importance of this param eter in T cell receptor recognition. Ultimately, particular T cell rec eptor sequences come to predominate in the secondary response and othe rs disappear, showing the selective presentation or expansion of speci fic T cell clones.