GVHD splenocytes proliferated poorly in response to LPS, and GVHD mice failed to generate increased total serum IgG2a and specific anti–HSV-1 IgG2a after viral inoculation. (A) Spleen-cell proliferative response to LPS or medium alone was measured. Representative B-cell numbers show that control and GVHD mice had similar B-cell numbers. The experiment shown is representative of four similar experiments. (B) Total serum immunoglobulin levels were measured by radial immunodiffusion before and 2 weeks following HSV-1 infection. Preinfection and postinfection serum results are shown. Each mouse group consists of three mice, and the mean and SEM are shown. This experiment is representative of three similar experiments. Significant differences (P < .05, t-test) are detected between total serum IgG2a levels in control group and the GVHD group after HSV-1 infection. (C) Serum levels of specific anti–HSV-1 IgG2a were determined by ELISA. The data shown are the mean and SEM of five similar experiments that included 15 mice. The IgG2a level of the GVHD group is significantly decreased compared with the IgG2a level of control mice (P < .05, t-test).