FIG. 4.

Effect of co-stimulation on splenic NK-cell expansion during acute MCMV infection. Wild-type C57BL/6 (WT), B7^−/− (B7KO), or CD28^−/− knockout (CD28KO) mice infected with Smith MCMV (5 × 10⁴ PFU) or vehicle had splenic tissues removed 2 or 6 dpi. Three hours prior to organ removal, each mouse received IP 1.0 mg BrdU. CD3⁻NK1.1⁺ gated splenocytes were enumerated and had division estimated by flow cytometry, as described in Fig. 3. (A) Representative flow cytometric plots 2 dpi. (B) Ly49H⁺ and Ly49H⁻ NK-cell numbers and BrdU incorporation in spleens over time. Each data point represents mean ± standard error for 3 mice. This experiment was performed twice with comparable results.