Despite a large number of T cells infiltrating the liver of patients with chronic hepatitis B, little is known about their complexity or specificity. To characterize the composition of these T cells involved with the pathogenesis of chronic hepatitis B (CHB), we have studied the clonality of V␤ T cell receptor (TCR)-bearing populations in liver tissue by size spectratyping the complementarity-determining region (CDR3) lengths of TCR transcripts. We have also compared the CDR3 profiles of the lymphocytes infiltrating the liver with those circulating in the blood to see whether identical clonotypes may be detected that would indicate a virusinduced expansion in both compartments. Our studies show that in most of the patients examined, the T cell composition of liver infiltrating lymphocytes is highly restricted, with evidence of clonotypic expansions in 4 to 9 TCR V␤ subfamilies. In contrast, the blood compartment contains an average of 1 to 3 expansions. This pattern is seen irrespective of the patient's viral load or degree of liver pathology. Although the TCR repertoire profiles between the 2 compartments are generally distinct, there is evidence of some T cell subsets being equally distributed between the blood and the liver. Finally, we provide evidence for a putative public binding motif within the CDR3 region with the sequence G-X-S, which may be involved with hepatitis B virus recognition. (HEPATOLOGY 2001;33:1288-1298.)Infection with hepatitis B virus (HBV) results in acute and chronic liver disease of variable severity, which is generally thought to arise from immune-mediated reactions. 1 This is because the virus is noncytopathic, and histopathologic studies of HBV-infected livers frequently show a large infiltration of inflammatory cells containing virus-specific HLA class I-restricted cytotoxic T lymphocytes. 2 Characterization of immune responses to human HBV infection have been hampered by the inability of the virus to infect hepatocytes in vitro and by the difficulty of studying the intrahepatic compartment. Most of the work has been performed with peripheral blood lymphocytes (PBL) because these are the only readily accessible source of antigen-specific cells. However, although the degree of cytotoxic T lymphocyte (CTL) activity demonstrable in the blood of patients with self-limited acute infections correlates with viral clearance in the liver, this response is barely detectable in the circulation of chronic patients despite clinical and histological signs of liver damage. 3 Some have argued that HBV-specific CTLs are preferentially sequestered in the liver, where they cause persistent hepatic damage without complete virus eradication. 4 The histopathology of HBV-infected livers is characterized by varying degrees of portal tract and parenchymal infiltration by CD8 ϩ and CD4 ϩ T lymphocytes, 2 but very little is known about the clonal composition of these liver-infiltrating lymphocytes (LIL). Studies using HBV peptide-loaded HLA-A2 tetramers to identify virus-specific CTL in chronically infected ...

With intensive mining of groundwater and expansion of irrigation area, reversion has happened to the grassland and arable area of West Liaohe River Plain, and the natural property of ecological system has declined sharply. Through historical literature research and plant sampling survey, comparison was made for the status dynamic change of grassland vegetation community on the West Liaohe River Plain before (1980) and after interference (2016). According to the result, it showed that the grassland vegetation species diversity of West Liaohe River Plain dropped from 917 to 258. Besides, the influence factors affecting vegetation community change were also analyzed, 1) the grassland was occupied by arable land, thus resulting in a shrink in grassland area from 48, 900 km2 in 1980 to 22, 400 km2 in 2016. Due to the locality in species distribution, therefore, the shrinking process of grassland also represented the process of species disappearance; 2) large-scale well irrigation resulted in the overall decrease of underground water level and the vegetation ecological degradation; 3) overgrazing and other problems brought by rapid development of animal husbandry.

The West Liaohe Plain is a typical semi-arid area, where the process of rainfall infiltration to replenish groundwater is a key link in its vertical hydrological cycle. In this paper, we compare and analyze the impact upon soil moisture movement and water infiltration after the shift of irrigation method from flood irrigation to mulched drip irrigation under mulch through setting up in-field in-situ observation points and carrying out groundwater depth dynamic observation. The results show that compared with mulched drip irrigation under mulch, flood irrigation has a stronger response to rainfall infiltration and a quicker response time in the rise of underground depth. With the decrease of groundwater level, the effect of rainfall infiltration to replenish groundwater is significantly weakened. In the flood irrigation area, the groundwater depth at about 8 m already has no obvious response to a small amount of rainfall. However, the groundwater depth at 6 m in the area of mulched drip irrigation under mulch already has no response to rainfall. Therefore, when groundwater extraction is carried out in irrigation areas, reasonable groundwater extraction levels should be designated in light of different irrigation methods to maintain the sustainable utilization of groundwater.

No abstract