Antigen-primed T cells cultured in IL-2 are bigger than T cells cultured in IL-15. (A) Live low-light digital camera images of 2-day antigen-primed CD8⁺ T cells cultured for 5 days in either 20 ng/mL IL-2 (CD8^IL-2) or 20 ng/mL IL-15 (CD8^IL-15). Cells were allowed to settle on glass coverslips coated with 5 ng/mL recombinant mouse ICAM-1/Fc chimera, and were filmed in RPMI 1640 (10% FCS, pentstrep, 50 μm β-mercaptoethanol) using an Axiocam digital camera supported by a motorized microscope (Carl Zeiss, Oberkochen, Germany). Cells were visualized under phase-contrast by a 40 ×/0.75 numeric aperture objective lens; resulting images were analyzed with Axiovision software (Carl Zeiss). (B) FACS dot plots of FSC and SSC profiles. (C) Cellular protein content. Dot plots and graphs are representative of the results of 5 or more experiments. P < .05 for protein concentrations. Error bars indicate SD.