Highly enriched T-TILs could not be expanded when stimulated with purified FL cells, even in the presence of IL-2 or costimulation. (A) T-TILs (<98% CD3⁺) from patient FL4 were stimulated with either unstimulated FL cells (▪) or unstimulated FL cells in the presence of 100 IU/mL IL-2 (•). (B) T-TILs (<98% CD3⁺) from patient FL4 were stimulated with either FL cells in the presence of B7-1 transfected NIH3T3 cells (▴), B7-2 transfected NIH3T3 cells (•), or FL cells in the presence of CD28 MoAb (10 μg/mL; ▪). The number of CD3⁺ cells equals the total number of viable cells during culture as determined by phenotypic analysis on days 7, 14, 21, and 28. Results are representative of three experiments with cells from patient FL4. Comparable results were obtained with FL cells from three additional patients.