Production of antibodies against antigens released from human pancreatic tumour xenografts

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Abstract
Antibodies directed against the antigen released from viable tumour cells during growth have been raised by cross-immunization of immunocompetent hairy litter-mates with serum from nude mice bearing pancreatic tumour xenografts. Antisera raised against the components released from a primary pancreatic tumour xenograft (WB) or from a tumour cell-line xenograft (GER) showed a titre greater than 1:625 against cultured pancreatic tumour cells by an I125-binding assay. Five out of 14 of the hairy litter-mates immunized with serum from the same tumour (GER) produced antisera that bound more strongly to pancreatic cancer cells than to 13 other non-pancreatic cell lines (binding ratio greater than 2). Absorption of the antisera with pure CEA reduced the level of binding by 11-25% without affecting the specificity for pancreatic tumour cells. The antibody response could be completely removed by absorption with pancreatic tumour cells, whereas 50% and 18% of the activity remained after absorption with normal pancreas homogenate and a mixed non-pancreatic tumour-cell pool, respectively. Immunofluorescent staining of pancreatic tumour sections indicated that the antibody was localized on the membrane of ductular epithelial cells. Challenge of immunocompetent mice using this procedure has produced a polyspecific antiserum with signs of selectivity for the circulating antigens released from pancreatic cancer cells, and may provide a route to the production of antibody against specific tumour components.