Characterization of anti-Citrobacter 036 specific polysaccharide monoclonal antibodies.

Monoclonal mouse antibodies specific for the 0 antigen of Citrobacter 036, a homopolymer of beta (1----2)-linked 4-deoxy-D-arabinohexose, were generated by the hybridoma technique. Balb/c mice were immunized with killed whole-cell vaccine and initial selection of active clones was based on enzyme-linked immunosorbent assay (ELISA) employing purified lipopolysaccharide (LPS). Concentrated culture supernatants from selected hybrid cultures were used to identify 10 0-antigen specific monoclonal antibodies using the multiple criteria of immunoprecipitation of 0 chains and LPS, inhibition by acid hydrolyzed 0 chains in the screening ELISA, and antibody class analysis. Four monoclonal antibodies were chosen for further study using dose-dependent 0-chain inhibition of ELISA and passive hemagglutination, passive hemolysis, and bacterial agglutination titres. When screened with Citrobacter serotypes known to contain the sugar 4-deoxy-D-arabinose, passive hemagglutination tests showed that the two monoclonal antibodies examined possessed titres which could be correlated with the reported 4-deoxy-D-arabinohexose content of the respective LPS's. This sugar is an antigenically important unit of several Citrobacter serotypes as defined by these well-characterized monoclonal antibodies.

Clonal variation and functional correlation of organ-specific metastasis and an organ-specific metastasis-associated antigen.

Monoclonal antibodies were used to probe the cell surface of organ-selected metastatic variant cells. Previously we defined a liver metastasis-associated antigen (LMAA) by means of the reaction of a monoclonal antibody with a liver metastasis selected tumour variant cell line, MDCC-AL2. The monoclonal anti-LMAA antibodies specifically inhibit liver metastasis of AL2. There is a correlated, clonal variation in LMAA expression and liver metastasis in both the AL2 cell line and an overy-selected metastatic variant MDCC-AL3. The variation in liver metaatatic ability is thought to represent clonal progression of the tumour cell lines. The LMAA probably represents only one of the ways in which a tumour cell may give rise to a live metastasis. Two hypotheses are discussed utilizing the LMAA in a functional role in the specific trapping of metastatic tumour cells in the liver or the successful colonization of the liver by metastatic tumour cells.

Detection of a cell-surface antigen correlated with organ-specific metastasis.

Despite the fact that tumour cells with the potential for metastasis may circulate randomly, many demonstrate a preference for specific organs. Recently, several investigators have selected variant tumour cell lines with enhanced capacity to metastasize to specific organs, mainly using the spontaneously originating B16 melanoma cell line of the mouse and tumour variants with enhanced capacity to metastasize to the lungs, brain and liver. We previously reported the derivation of a liver-specific metastatic variant of a Marek's disease (MD) virus-transformed, non-producer lymphoma cell line. MD is a naturally occurring, herpes virus-induced, T-cell lymphoma of chickens which bears pathological and aetiological similarities to Burkitt's lymphoma in man. This makes MD a useful model for study. One similarity is the pattern of metastasis in which both lymphomas induce a high incidence of ovarian and liver lesions. We now report the existence of a cell-surface antigen, detectable by a monoclonal antibody, correlated with organ-specific metastasis.

Selection for virulence and organ-specific metastasis of herpesvirus-transformed lymphoma cells.

The Marek's Disease virus-transformed, non-producer, lymphoma cell line, MDCC-RPI, was selected by sequential transplantation to produce a highly malignant variant, MDCC-ALI. This is evidenced gy an 18-fold decrease in LD50. The new cell line has an increased ability to form metastatic lesions in a distribution which mimics the natural disease. Further selections for organ-specific metastasis were undertaken with the isolation of two cell lines, MDCC-AL2, selected for liver metastasis, and MDCC-AL3, selected for ovary metastasis. In vivo studies show that the selection was unsuccessful in the case of the ovary but successful in the case of the liver. Two assays were developed, utilizing the chick embryo and intravenous injection of lymphoma variants. One measures liver-specific metastasis by the enumeration of tumor foci on the embryonic liver. The second, chorioallantoic membrane (CAM) focus formation, correlates with the virulence of the injected lymphoma cells. The liver-selected tumour variant cells form more liver foci than any other tumour variant cells. The genetic background of the embryo does not affect formation of liver foci. Resistance to CAM focus formation correlates with major histocompatibility complex associated resistance to MD.