Human lymphocyte response to CEA: Titration of different CEA samples and neutralization experiments with monoclonal anti-CEA antibodies

Abstract By means of the macrophage electrophoretic mobility technique a striking digestive system cancer-associated human lymphocyte response to CEA has been found during a large-scale study including tests in 499 individuals. The question to be answered by this study was whether this response is really CEA-specific. Titration experiments with 3 different CEA preparations in lymphocytes from 5 colorectal cancer patients showed that the threshold dose of CEA necessary to induce lymphocyte responses amounts to 50–100 ng CEA per ml and 10 6 lymphocytes, regardless of the CEA origin and its state of purity. The CEA specificity of the responses was proved by neutralization experiments with 3 CEA-specific monoclonal antibodies. When allowed to react with CEA before lymphocyte incubation, the MABs prevented CEA from inducing lymphocyte responses. Appropriate murine control myeloma protein did not influence these responses. The reactivity of these lymphocyte samples to a teratocarcinoma extract could not be prevented by treating this material with CEA-specific MABs before incubation. Preliminary attempts to enrich the lymphokine(s) released after CEA stimulation resulted in recovery of the activity within 2 arbitrarily cut Sephadex G-100 fractions comprising the mol. wt range of 3000–47000.