Short-term IL-7 administration alters the expression of CD11a (LFA-1) in naive cells in the absence of T-cell activation. Histogram plots of CD11a expression in lymph node-derived naive CD44lo CD4⁺ and CD8⁺ cells in diluent control and rmIL-7-treated (5 μg per day for 7 days) thymus-intact mice are shown (A). Mean fluorescent intensity (MFI) of CD11a was consistently higher in cells from rmIL-7-treated mice. Numerical values represent the MFI plus or minus SD of 7 mice per group. Similar increases in CD11a MFI were observed in spleen- and PBL-derived naive T cells (data not shown). In contrast, administration of rmIL-7 did not induce expression of the T-cell activation markers CD69, CD25, or CD71 (B). Solid lines represent histograms of diluent-treated control mice, dotted lines represent histograms of rmIL-7-treated mice, and dashed lines represent histograms of normal splenocytes that were stimulated in vitro with anti-CD3 (2C11) antibody serving as a positive control for CD69, CD25, and CD71 expression. Shown are representative data from 7 mice. Similar patterns of CD11a and T-cell activation marker expression were observed in rmIL-7-treated thymectomized mice and in thymus-intact and thymectomized mice treated with rmIL-7 for 14 days (data not shown).