Complementation of anti‐CEA and anti‐TAG‐72 monoclonal antibodies in reactivity to human gastric adenocarcinomas

Monoclonal antibody (MAb) B72.3 and MAb COL‐4 are reactive with the high‐molecular‐weight (Mr > 10⁶) tumor‐as‐sociated glycoprotein (TAG)‐72, and the Mr 180,000 carcino‐ embryonic antigen (CEA), respectively. Antibody competition radioimmunoassays (RIAs) using ¹²⁵1‐MAb B72.3 or ¹²⁵1‐COL‐4 have demonstrated that each MAb also recognizes a distinct antigenic determinant. Solid‐phase RIAs using MAbs B72.3 and COL‐4, however, demonstrated similar reactivity for each MAb with gastric carcinomas versus normal gastric mucosa. Tissue sections from ail of 17 gastric adenocarcinomas also reacted with both MAb B72.3 and MAb COL‐4 when immunoperoxidase techniques were used. Double‐staining techniques using both MAbs on the same section were performed on formalin‐fixed, paraffin‐embedded gastric tissue sections using the combination of avidin‐biotin peroxidase complex and avidin‐biotin alkaline phosphatase complex immunohis‐tochemical methods. The double‐staining technique revealed that some carcinoma cells react with MAb B72.3, some react with MAb COL‐4, and others react with both MAbs. This technique has demonstrated that more carcinoma cells can be detected by both MAbs as compared to the number of stomach carcinoma cells shown to be reactive with either one or the other MAb. These studies thus define the rationale for the use of combinations of MAbs which recognize different tumor‐associated antigens as immunological adjuncts for detection and perhaps therapy of gastric carcinoma.