| Previous studied found that more leukocytes(lymphocytes,neutrophils,etc)accumulated in the alveolar lavage fluid of obese mice following E.coli infection,and the lung tissue structure returned to normal faster than non-obese mice,suggesting that obesity can enhance the defensive function of lung and promote the repair of injured tissues in mice.Obesity can alter the cellular immunity by the change of T lymphocyte subsets.“The spleen is the largest immune organ of the body”has been recognized,while the intestine has become one of the most important immune organs by the storage of the largest lymphocyte population in the body.However,there are few studies on the effects of obesity on intestine and spleen under the condition of pulmonary infection.Therefore,this experiment aims to explore the effects of obesity on cellular immune function of spleen and intestine by detecting the T lymphocyte subsets and histopathology of spleen and intestine.Experiment Ⅰ:effects of obesity on T lymphocyte subsets of blood,spleen and intestine following E.coli infection.The specific pathogen free(SPF),male,35~38 g and non-obese Kunming mice were randomly divided into group Ⅰ(n=32)and Ⅱ(n=32).The SPF,male,46~50 g and obese Kunming mice were randomly divided into group Ⅲ(n=32)and Ⅳ(n=32).Mice in group Ⅱ and Ⅳ were intranasally instilled with 40μL E.coli suspension(4×10~9 CFU),and group Ⅰ and Ⅲ with the equal volume of phosphate buffered saline.The blood,spleen and intestine were collected to analyse T lymphocyte subsets by flow cytometry at 0 h,12 h,24 h and 72 h post-infection.The results are as follows:(1)The percentage of CD4~+and CD8~+cells of blood in group Ⅲ was higher than that in group Ⅰ(P<0.05).There was no significant differences in the percentage of CD3~+,CD4~+,CD8~+cells and the ratio of CD4~+/CD8~+of spleen between group Ⅰ and Ⅲ(P>0.05).There was no significant differences in the percentage of CD3~+,CD4~+,CD8~+cells and the ratio of CD4~+/CD8~+of IELs between group Ⅰ and Ⅲ(P>0.05).The percentage of CD3~+cells of LPLs in group Ⅲ was lower than that in group Ⅰ(P<0.05).(2)There was no significant differences in the percentage of CD3~+,CD4~+,CD8~+cells and the ratio of CD4~+/CD8~+of blood between group Ⅰ and Ⅱ(P>0.05).Compared with group Ⅰ,the percentage of CD4~+cells of spleen in Ⅱ was significant increased after infection(P<0.05),the percentage of CD8~+cells was significant decreased after infection(P<0.05),the ratio of CD4~+/CD8~+was significant increased after infection(P<0.01);the percentage of CD4~+cells of IELs in group Ⅱ was significant decreased after infection(P<0.05);the percentage of CD3~+,CD4~+and CD8~+cells of LPLs in group Ⅱ was significant decreased after infection(P<0.05).(3)Compared with group Ⅲ,the percentage of CD4~+and CD8~+cells of blood in Ⅳ was significant decreased after infection(P<0.05);the percentage of CD3~+,CD4~+and CD8~+cells of spleen in group Ⅳ was significant decreased after infection(P<0.05);the percentage of CD3~+cells of LPLs in group Ⅳ was significant decreased after infection(P<0.01).(4)The percentage of CD4~+cells and the ratio of CD4~+/CD8~+of spleen in group Ⅱ was higher than that in group Ⅳ after infection(P<0.05).The percentage of CD4~+cells of IELs in group Ⅱ was lower than that in group Ⅳ after infection(P<0.05).The percentage of CD3~+cells of LPLs in group Ⅱ was higher than that in group Ⅳ after infection(P<0.05);the percentage of CD8~+cells was lower than that in group Ⅳ at 12 h and 24 h post-infection(P<0.05).Experiment Ⅱ:effects of obesity on the histopathology of spleen and intestine following E.coli infection.The same administration of experiment I was also used in this experiment.The spleen,duodenum and colon were harvested to detect the tissue structure,IELs,paneth’s cell,goblet cell and ⅠgA~+cells at 0 h,12 h,24 h and 72 h post-infection.The results are as follows:Histopathological results showed that the spleen structure of obese mice was different from that of normal mice,the germinal center was observed only in obese mice.The white pulp area of obese mice was larger than that of normal mice,but there was no significant difference(P>0.05).The white pulp area was increased following E.coli infection,but only the area of white pulp in Ⅳ,compared with Ⅲ,showed a significant difference at 24 h post-infection(P<0.05).Obesity and E.coli infection had no effect on the histological structure of duodenum and colon,as well as the number of IELs and paneth’s cell.However,obesity can increase the number of ⅠgA~+cells of duodenum and goblet cells of colon.After infected with E.coli,the ⅠgA~+cells of duodenum and the lymphocytes of colon were increased both in obese and non-obese mice,but the change in obese mice was greater.Conclusion:Obesity can increase the number of CD4~+and CD8~+cells in the blood of mice and enhance the intestinal mucosal immune function,which improving the ability to remove pathogens.Only the number of CD4~+and CD8~+cells in the blood of obese mice changed significantly after infection,and only the percentage of CD3~+cells in the spleen of obese mice decreased significantly after infection,suggesting that obese mice are more sensitive to E.coli. |
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