Expression levels of amino acid transporter CD98 (42F) and transferrin receptor CD71. (A-B) FACS histograms of the expression of CD98 and CD71 on antigen-activated P14 LCMV CD8⁺ T cells cultured in 20 ng/mL IL-2 (CD8^IL-2), 20 ng/mL IL-15 (CD8^IL-15), or medium alone for 24 to 48 hours. (C) FACS histograms show expression levels of L-selectin (CD62L) and the common γc chain cytokine receptor subunit on antigen-activated P14 LCMV CD8⁺ T cells cultured in 20 ng/mL IL-2 (CD8^IL-2), 20 ng/mL IL-15 (CD8^IL-15), or medium alone for 24 to 48 hours. Histograms are representative of the results of 7 or more experiments.