Objective To explore the expression ofapoptosis inducing factor (AIF) and the apoptosis ofnervous cells in infectious brain injury rat models induced by pneumolysin (PLY) and their significance.Methods A total of 80 infant SD rats were randomly divided into normal saline treatment group (NS group,n=40) and PLY treatment group (PLY group,n=40).Each group was divided into 4 subgroups:NS observation subgroups at the 6,12,24 and 48 h of treatment and PLY observation subgroups at the 6,12,24 and 48 h of treatment (n=10).Five rats in these subgroups were injected with Evan' s blue (EB) to determine the damage of BBB by measuring the content of EB in the brain tissues;the other 5 rats in these subgroups were not given EB,and their brain tissues were obtained to detect the protein expressions of NSE,GFAP and AIF by immunohistochemistry,and their apoptosis was examined by TUNEL staining.Results As compared with those in the NS treatment subgroups,the brain EB content and the expression levels of NSE,GFAP and AIF in the PLY treatment subgroups were significantly higher,and the number of apoptotic cells was significantly increased (P＜0.05).The number of apoptotic cells was positively correlated to the protein expression level of AIF in the PLY treatment group (r=0.959,P=0.000).Conclusion Apoptosis plays a role in the formation and development of infectious brain injury of rats and AIF might involve in the apoptosis ofneurocyte.