Correlation Analysis Of Dendritic Cells And T Cell Levels In Mice At Different Stages Of Listeria Monocytogenes Infection

Listeria monocytogenes is a zoonotic foodborne pathogen that can cause gastroenteritis,meningitis,sepsis,miscarriage,and other diseases in humans and animals.Listeria monocytogenes is an intracellular parasite,and its elimination by the host relies on cellular immunity.Dendritic cells,as the antigen-presenting cells that have been found to have the most powerful antigen presenting function,play a key role in the initiation of L.monocytogenes T cell immune responses.At present,there have been a large number of studies on the regulation of T cell response by dendritic cells in vivo after infection with Listeria,whilie there is no systematic analysis of the correlation between dendritic cells and T cell levels at different stages of Listeria infection.Therefore,in order to investigate the dynamic changes of dendritic cells and effector cells at different stages of life after infection with Listeria monocytogenes in vivoand the relationship between this change and bacterial load,we conducted the following research work:(1)Determination of bacterial load in spleen and liver of C57BL/6 mice infected with Listeria monocytogenes.C57BL/6 mice were infected with Listeria monocytogenes and the proliferating bacteria were detected in the spleen and liver one day after infection.In the spleen,the bacterial load increased rapidly on the second day of infection and was increased on the third day.Slowly,it quickly increased and reached its highest value on the fourth day.After the fifth day,the bacterial load began to drop rapidly.In the liver,the bacterial load rapidly increased on the second day of infection,and increased slowly after the third day.After 7 days of infection,the spleen and liver of some mice could not detect the presence of bacteria.(2)Changes in monocyte ratio in spleen at different stages of L.monocytogenes infection in C57BL/6 mice.We measured the proportion of mononuclear cells at different times of infection in the spleen of mice.The result showed that mononuclear cells were rapidly elevated in C57BL/6 mice after two days of infection with Listeria monocytogenes and peaked on the fourth day After reaching the peak,it begans to decline,corresponding with the bacterial load in the spleen.It was found that the mononuclear cells in the spleen did not proliferate during the first plateau of bacterial proliferation,but began to increase in the second bacterial proliferation.(3)Changes of dendritic cells in spleen of C57BL/6 mice infected with Listeria monocytogenes at different stages.The proportion of DCs in the spleen of C57BL/6 mice infected with Listeria monocytogenes rapidly decreased with the increase of bacterial load,and the DC ratio began to recover when the bacterial load began to decline.The proportion of CD8~+DC subpopulations that had an important role in the infection of Listeria began to decline,and when the bacterial load entered the second proliferative phase,the proportion of this subpopulation increased and then decreased again.The proportion of CD8~-DC subpopulations did not change significantly in the initial stage of infection,but when the bacteria proliferate into the second proliferative cycle,the subpopulations increased to a certain extent.(4)Immune response of L.monocytogenes to CD4+T cells and CD8+T cells in C57BL/6mice infected with Listeria monocytogenes at different stages.The proportion of CD4+T cells in the spleen rapidly decreases at the initial stage of infection with Listeria monocytogenes,and CD4~+T cells remain at a low level as the bacterial load rises.When bacterial load peaks in the spleen,the proportion of CD4~+T cells began to rise rapidly,and the proportion of CD4~+IFN-?~+T cells was maintained at a low level.in the bacterial proliferative exponential phase.When the bacterial load peaked,the proportion of CD4~+IFN-?~+T cells began to increase significantly,which was basically in sync with the change in the proportion of CD4~+T cells.At the same time,our results showed that the level of DC cells in the spleen is basically consistent with the level of CD8~+T cells,both of which have decreased in the early stage of bacterial infection,and the levels of the two increased as the bacterial load reaches a peak.(5)Changes of other effector cells in different stages of Listeria monocytogenes infection in C57BL/6 mice.The percentage of C57BL/6 mice infected with L.monocytogenes regulatory T cells was always decreasing,NK cells first increased and then decreased,and finally remained stable,with no significant changes in B cells.(6)Detection of liver and spleen pathological changes in mice at different stages of Listeria monocytogenes infection.After C57BL/6 mice were infected with Listeria monocytogenes,the mice spleen became larger,the inflammatory cells in the white pulp were destroyed,the inflammatory cells infiltrated,and the cells appeared necrotic.The nucleus in the necrosis area was pyknosis,fragmentation and dissolution disappeared.The round vacuoles of varying sizes in the liver cells,the nucleus is squeezed to one side,the cytoplasm is reduced,the hepatocytes are obviously swollen and the cytoplasm is faded,fat lesions occur,vacuoles of different sizes appear,and part of the nucleus is biased towards the cells.