Studies of Some Antigens of the L Strain Mouse Fibroblast23

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Abstract
Agglutination, complement-fixation, and metabolic inhibition reactions were used to compare the cross-reactivity of the L strain mouse fibroblast with other cell strains grown in vitro. A high degree of cross-reactivity was observed between 2 lines of mouse fibroblasts (strains L and LLC-M1) or between 2 lines of human epithelial cells (HeLa and Chang liver). A lower order of cross-reactivity was noted between the fibroblasts and epithelial cells. No antigenic differences could be detected between strain L and strain LLC-M1 fibroblasts. Metabolic inhibition titers of heat-inactivated antiserums to fibroblasts strains L or LLC-M1 were found to be low. With the addition of fresh guinea-pig serum, the inhibition titers increased fivefold. A serologic characterization was undertaken of the surface antigens of the strain L cells. Cells were treated with several enzymes or chemical agents known to have effects on different chemical groupings. It was found that treatment with sodium periodate or lipase abolished the agglutination of cells by antiserum prepared against whole, untreated cells. Trypsin, pancreatin, and collagenase, in low concentration, increased the titer. With higher concentrations or prolonged exposure to trypsin, there was a nonspecific aggregation of cells. Several chemical procedures were used to fractionate the strain L cells and prepare antigens of varying chemical composition. A water-methanol extract of the fibroblasts stimulated the production of agglutinating, complement-fixing, and cytotoxic antibodies reacting with whole cells. Antibodies to this antigen cross-reacted with strain LLC-M1.