Rat small intestinal epithelial cell lines have been established in vitro and subcultured serially for periods up to 6 mo. These cells have an epithelioid morphology, grow as monolayers of closely opposed polygonal cells, and during the logarithmic phase of growth have a population doubling time of 19-22 h. Ultrastructural studies revealed the presence of microvilli, tight junctions, an extensive Golgi complex, and the presence of extracellular amorphous material similar in appearance to isolated basement membrane. These cells exhibit a number of features characteristic of normal cells in culture; namely, a normal rat diploid karyotype, strong density inhibition of growth, lack of growth in soft agar, and a low plating efficiency when seeded at low density. They did not produce tumors when injected in syngeneic animals. Immunochemical studies were performed to determine their origin using antisera prepared against rat small intestinal crypt cell plasma membrane, brush border membrane of villus cells and isolated sucrase-isomaltase complex. Antigenic determinants specific for small intestinal epithelial (crypt and villus) cells were demonstrated on the surface of the epithelioid cells, but they lacked immunological determinants specific for differentiated villus cells. An antiserum specifically staining extracellular material surrounding the cells cultured in vitro demonstrated cross-reactivity to basement membrane in rat intestinal frozen sections. It is concluded that the cultured epithelioid cells have features of undifferentiated small intestinal crypt cells. KEY WORDS small intestine epithelioid cell cultures cell-specific antigensSmall intestinal epithelial cells represent a rapidly renewing cell population characterized by a precise segregation between mitotically active cells, present in the crypt region, and mature differentiated villus cells, mitotically inactive. Intestinal cells have a rapid cell turnover, with a mean cell duration time of 2-3 d in most animals (5,6,8,27). The differentiation of the mitotically active crypt cells is accompanied by dramatic changes in enzyme and transport activities and in cell morphology, including the appearance of a well-organized brush border at the luminal surface and a more columnar cell shape. It is of interest that, although intestinal crypt cells have one of the shortest cell cycle times in vivo (5), the occurrence 248 J, CELL BIOLOGY 9 The Rockefeller University Press

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These results suggest that the high rate of chronic HCV infection in alcoholics may be due to ethanol's effects on antiviral immune responses.

Hepatitis C virus (HCV) represents a major cause of posttransfusion hepatitis worldwide. Posttransfusion hepatitis associated with hepatitis B virus (HBV) continues to occur. HBsAg-negative donor sera from the Rhode Island Blood Center between 1987 and 1988 were screened using more sensitive techniques to assess the prevalence of low level HBV infection. Group I consists of 866 healthy blood donors without HBV serologic markers, group II consists of 377 donors with ALT elevations (> 45 IU/L), group II consists of 148 donors positive for anti-HBc, and group IV consists of eight donors positive for both surrogate markers. A sensitive monoclonal immunoradiometric assay (M-IRMA) was employed for detection of HBsAg-associated epitopes (detection limit of 20 pg/ml) in serum. A subset of sera were analyzed for the presence of HBV DNA using the method of anti-HBs capture of HBV related virions in serum followed by polymerase chain reaction (PCR) amplification. Using these techniques, 0.8% and 1.7% of donors were positive for HBsAg and HBV DNA respectively in group I. In contrast, 0.9% and 9.5% in group II and 0.7% and 18.1% in group III were positive, respectively. There were eight donors with both ALT elevation and anti-HBc; and four (50%) of these were positive for HBV DNA. In the group with anti-HBc, the majority (80%) of donors with HBV DNA had either no or low (signal to noise ratio < 10) anti-HBs titer. Using anti-HCV testing and reverse transcription-PCR for detection of HCV genomes, we detected evidence of HCV infection in nine of the 49 donors with low level HBV DNA.(ABSTRACT TRUNCATED AT 250 WORDS)