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We demonstrate that human fibroblasts of the rare pk phenotype lack globoside, which was identified as the blood group P antigen, and that p cells possess neither globoside nor trihexosyl ceramide, which was identified as pk antigen. Our investigations indicate also that these glycosphingolipid patterns are most likely caused by inherited preferential biosynthetic pathways in the abnormal phenotypes rather than by excess catabolism of the antigens. Evidence is presented that the fibroblasts of pk phenotype lack fl-N-acetylgalactosaminyltransferase (globoside synthetase; UDP-Nacetylgalactosamine:trihexosylceramide fi-N-acetylgalactosaminyltransferase; EC 2.4.1.79) activity, and those of p are deficient in a-galactosyltransferase (trihexosylceramide synthetase; UDP galactose:lactosylceramide a-galactosyltransferase) and possibly also in globoside synthetase. The diminished globoside synthetase activity in p cells, however, is not caused by the defect in the gene coding for this enzyme. It appears, rather, to be caused by a failure in gene expression because one-third of pk X p hybrids became able to express P antigenicity with a time

A monoclonal antibody, gamma-120, was raised against a highly purified gamma-glutamyltransferase (gamma GT) from human primary hepatoma. The antibody preferentially bound to the small subunit of gamma GT from human hepatoma and kidney as evidenced by immunoblot analysis. Weak binding to the normal liver enzyme could be detected by solid-phase enzyme-linked immunosorbent assay (ELISA). With the use of this antibody, an ELISA was developed for the quantitation of immunoreactive gamma GT in human serum. Sera of 188 normal control subjects displayed a low level (9.4 micrograms/ml) of immunoreactive gamma GT. Highly elevated levels of immunoreactive gamma GT were detected in the sera of patients with primary hepatoma, metastatic liver cancer, pancreatic cancer, and certain types of lung cancer. Slightly elevated levels of immunoreactive gamma GT were seen in the sera of patients with liver cirrhosis. The levels of gamma GT were within a normal range in the sera of patients with gastrointestinal cancers and patients with nonmalignant diseases such as hepatitis and gallstones. The antibody has been shown to be useful for the diagnosis of some of the neoplastic diseases.