FIG. 4.

NK cells affect CD8⁺ T-cell IFN-γ production, but addition can compensate for the loss of CD4⁺ T-cell help. C57BL/6 mice with HSV memory were divided into five groups: (i) depleted of NK cells (NK⁻), (ii) depleted of CD4⁺ T cells (CD4⁻), (iii) depleted of CD4⁺ T cells but supplemented with NK (CD4⁻ NK⁺⁺), (iv) supplemented with NK cells (NK⁺⁺), and (v) receiving control IgG. All the mice were given 1 × 10⁵ PFU of HSV and 5 days later were analyzed for IFN-γ production by CD8⁺ T cells to measure recall responses. The patterns were similar in all three experiments. A representative plot of intracellular IFN-γ staining in peptide-stimulated CD8⁺ T cells is shown. The data represents one mouse from each of the following groups: uninfected control, control IgG, CD4⁻, NK⁻, CD4⁻ NK⁺⁺, and NK⁺⁺. The number within the plot is the mean ± SD for five mice in each group. The differences between the NK⁺⁺ group and the CD4⁻ and NK⁻ groups were statistically significant (P < 0.005). The difference between the NK⁺⁺ and CD4⁻ NK⁺⁺ groups was significant (P < 0.01).