Objective To investigate the changes and mechanisms of immune function after ischemic stroke by studying the reaction of C57BL/6mice's lung and spleen after ischemic stroke.Methods Sixteen mice C57BL/6 were randomly assigned to experiment group (n=8) and control group (n=8).The acute ischemic stroke model was established in experiment group by Middle Cerebral Artery Occlusion (MCAO) and no stroke was performed in control group.Then we observed the lung inflammation by HE staining of the lung.And we measured the spleen weight,spleen weight index,the count and the apoptosis index of spleen cells of mice in two groups.Results Compared with the control group,the count of the inflammatory cells in lung of mice in the experiment group was higher,the spleen weight,spleen weight index and spleen cells count of the experiment group were decreased and the apoptosis index of spleen cells of the experiment group was higher.Conclusion The mice in the experiment group have inflammatory reaction in lung,the spleen atrophied and the apoptosis index of spleen cells is increased,which suggest that stroke-induced apoptosis of immunocytes may cause immunodepression after ischemic stroke and easily lead to the infection.