Reactivity of HLA-DP4-restricted NY-ESO-1-specific CD4+ T cells clones against different concentrations of NY-ESO-1 p157-170. Seven CD4+ T cell clones obtained from patients NW1454 and NW1662 were tested against different concentrations of NY-ESO-1 p157-170 in ELISPOT assays. Depending upon the interclonal avidity, different levels of peptide concentration are required for detectable reactivity with the respective CD4+ T cell clone.