Postsplenectomy sepsis in splenectomized, partially splenectomized and non-splenectomized rats after Streptococcus pneumoniae challenge

Introduction: Purpose of the study was the evaluation of the role of 1/3 of the spleen in host defense after a challenge with Streptococcus pneumoniae.

Materials and methods: Forty Wistar rats divided into four groups underwent splenectomy (SPR), partial splenectomy (PSR) or sham operation (SOR). Healthy rats were used as controls (CGR). Operations were performed under general anesthesia. Ten weeks after operation the rats were challenged with 6 × 107 cfu/ml Streptococcus pneumoniae administered intravenously. All surviving animals were sacrificed 12 days after intravenous injection Interleukin-10, tumor necrosis factor-α and human β-defensin-2 containing cells were detected in the parenchymatous organs (spleen, lungs, liver and kidneys) of all groups. Kaplan-Meier and Mann-Whitney tests were used for statistical analysis.

Results: Survival after Streptococcus pneumoniae challenge was longer in animals with a greater amount of splenic tissue, with mortality increased proportionately to the reduction in splenic tissue. In the SOR group survival was 11.6 ± 1.3 days (10% mortality). In the PSR group survival was 6.0 ± 2.5 days (90% mortality). In the SPR group survival was 1.6 ± 0.8 days (100% mortality). In splenic tissue the levels of HβD-2, IL-10 and TNF-α-containing cells did not differ statistically (z=5.021; p<0.01) and were higher than in other parenchymatous organs (PSR, SOR, CGR). Levels of IL-10-containing cells were higher in parenchymatous organs of the SPR group (z=7.919; p<0.001), similar in the PSR and SOR groups (z=1.020; p=0.308) and lower in the CGR group (z=4.366; p<0.01). There were no statistically significant differences in the levels of IL-10 containing cells in the lungs of all group rats with spleen (z=4.266; p<0.01). Levels of TNF-α-containing cells were similar in PSR and SOR groups (z=1.004; p=0.315). Relative levels of HβD-2 in kidney differed between all groups (z=2.916; p=0.004).

Conclusions: All of the splenectomized animals (100%) and 90% of the partially splenectomized animals died. Partial splenectomy (with 1/3 of splenic tissues remaining) does not offer full protection against Streptococcus pneumoniae sepsis. In all groups, the amounts of HβD-2, IL-10 and TNF-α-containing cells in the spleen were higher than in other parenchymatous organs (lungs, liver and kidneys).