The Study Of NK And NKT Cells In The Model Of Experimental Silicosis Rats

Background:Silicosis is a disease with a featuer of pulmonary fibrosis, a large number of long-term inhalation of dust which containing high silica content. If in a enviroment with high silica for a long-term, even out of this enviroment, silicosis will continue. There is a minimum amount of dust, which has been confirmed by Dale W Porter.The incidence of silicosis is high in China,it has become a severe occupational disease which endanger the health of workers, and with high fatality, so the prevention and treatment of silicosis remain the focus of occupational disease at the present and in the future. The basic lesion of silicosis is characteristic lesion formation of silicon nodules and diffuse interstitial fibrosis. The pathogenesis is complex so far. There are theories of lipid peroxidation,mechanical stimulation,cytokines and so on. The immune mechanism needs study comprehensively.NK cells is a cell population of hererogeneity and versatility, is different from the T and B lymphocytes.It not only plays a role in immune regulation by killing target cells directly, but also has a dual role of immune barrier and immune surveillance. It has caused great concern of the academic. NKT cells is a group of cells between NK and T cells,it also express a variety of surface marker of NK and T cells. It plays an important role in a variety immune response of organisms, such as anti-microbial infection, the occurrence of antoimmune disease, graft survival, and anti-tumor and so on. This study is to detect the changes of NK and NKT cells in peripheral blood in silicosis rats by flow cytometry, to explore the relationship between NK and NKT and silicosis. This a basic research of the immunological mechanism of silicosis. In the early stage of the experiment we found that NK cells were divided into two distinct groups, NKR-PlAdim and NKR-PlAbright, therefore,this article will explore the correlation between the changes and clinical significance.Objective:To investigate the changes and significance of NK cells,NK cell subsets (NKR-PlAdim and NKR-PlAbright) and NKT cells in peripheral blood at different times in Silicotic rat model.Methods:Forty eight healthy male SD rats were randomly divided into silica exposed group and control group. One/ml silica suspension(40mg/ml) was administrated via intratracheal instillation at one time while equal amount of saline was instilled to the rats of control group. Animals were sacrificed at the day 1,7,14,21,28 and 35(d) after instillation, and the peripheral blood samples were collected. The levels of NK (CD3-/7CD161+) and NKT(CD3+/CD161+) cells in peripheral blood were detected by flow cytometry. Thirty six healthy male SD rats were randomly divided into silica exposed group and control group.1ml silica suspension(40mg/ml) was administrated via intratracheal instillation at one time while equal amount of saline was instilled to the rats of control group. Animals were sacrificed at the day 1,4,7,10,13 and 16(d) after instillation, and the peripheral blood samples were collected. The levels of NKR-PlAdim and NKR-PlAbright cells in peripheral blood were detected by flow cytometry.Results:NK cells in peripheral blood of silicotic rats started to increase on the first day after silica instillation(P<0.05).The peak number appeared at week 3. It began to decrease after wards, but was still higher than that in the control group. NKT cells decreased (P<0.05)in the early stage obviously. The number of NKT cells increased later on, but was still lower than that in the control group. The NK cell subsets is mainly NKR-PlAbright in the peripheral blood of the silicotic rats, barely to the NKR-PlAdim subset. The NK subsets NKR-PlAdim and NKR-PlAbright appears at day 4.Then the NKR-PlAdim increased later on. The peak number appeared at 10 days. The difference between control and model group is significant (P<0.05).Then its proportion is gradually reduced. NK cells were mainly dominated by NKR-PlAbright.We will see no NKR-PlAdim subsets 16 days later. NK cells appears two subsets in the early stage of the experiment.Conclusion:Silica induces rat innate immune responses. NK and NKT cells play roles in the development of silicosis. In peripheral blood of silicotic rats there is a change in the percentage of NKR-PlAdim and NKR-PlAbright in the early stage.