A comparison of the KT64/BBL aAPC platform with previously established methods for TIL expansion. (a) TILs undergo extensive cell division when stimulated with aAPC at the 2:1 aAPC to T cell ratio. TILs or peripheral blood T cells were labeled with CFSE and stimulated with aAPC at either 0.5, 2, or 5 to 1 ratios with TILs, REM, CD3/28 beads or 600 IU/mL IL-2. Cell division was measured using CFSE dilution by CD3+ T cells 6 days after stimulation. (b) TILs rapidly expand in response to aAPC or REM-based expansion. Seven different TIL cultures established in IL-2 were stimulated using either KT64/BBL aAPC loaded with anti-CD3 antibody and supplemented with 100 IU/mL IL-2 (aAPC); rapid expansion with anti-CD3 antibody, high-dose IL-2 (6000 IU/mL) and excess allogeneic feeder cells (REM); anti-CD3/28 antibody-coated beads stimulation at a 3:1 bead to TIL ratio (CD3/28); continued culture in 600 IU/mL IL-2 (IL-2); or culture medium alone. Results reflect the mean ± SEM day 9 viable cell counts for 6 independent expansions. (c) Robust secondary TIL expansion was achieved using the aAPC platform. Secondary TIL expansion was initiated 12 days after primary aAPC stimulation and cultured for an addition 13 days. Values represent the mean of three TIL expansion ± SEM. Arrow indicates the time of secondary stimulation.