Histopathological examination of spleens of mice infected with 2009 H1N1 virus. The experiment set up is the same as in Figure 1. Compare to the control in different age groups (A-C), there was no significant difference at 1 day after except 1 year group with little increased phagocytes (D-F). At day 3 after H1N1 challenge, all three age groups presented hyperemia. The number of phagocytes (green arrow) in red pulp increased and lymphocytes in the white pulp decreased with age increased (G-I). At day 5 there was more severe hyperemia and focal haemorrhage than that at day 3 in each group. However, at 6 month group and 1 year group, hemosiderin (red arrow) could be easily seen in white pulp and red pulp with more severe decrease and apoptosis-like lymphocytes with age increased(J-L). (M) was the semi-quantitative histological analysis of spleen damage. *, ** and ***indicate P < 0.05, P < 0.01 and P < 0.001 respectively relative to the corresponding the different age group mice with 4 week age group mice. Mean ± SEM. n = 3 mice in each group. Magnification,× 400 (A-L).
Sun et al. Virology Journal 2011 8:52 doi:10.1186/1743-422X-8-52