Radioisotopic 15Cr-Leukocyte adherence inhibition (LAI) assay. I. Demonstration of anti-tumor immunity in patients with breast carcinoma

a simplified radioisotopic leukocyte adherence inhibition assay (⁵¹Cr-LAI assay) was used to determine tumor-directed immune responses in patients with cancer of the breast. Essential steps in development of this assay are the standardization of conditions for optimal ⁵¹Cr uptake by peripheral blood lymphocytes (PBL) and the inclusion of autologous or normal AB serum in the incubation media. A dextrose salt mixture (GNK) was found to enhance intracellular uptake of ⁵¹Cr significantly (8-fold) without affecting viability of the cells or without causing selective loss of lymphocyte subpopulations. The presence of 10% autologous or normal AB serum prevented non-specific LAI responses to unrelated tumor antigens.In a study of 46 preoperative patients with suspected breast cancer, clear and accurate prediction of the presence of cancer was achieved with this new assay. All patients with localized breast cancer showed significant adherence inhibition in response to allogeneic breast tumor extracts whereas normal control women and patients with benign disease did not respond. Neither patients with cancer nor those with benign breast diseases reacted to extracts of benign breast tissue antigens. LAI reactivities appeared to be directed selectively against tumor-associated antigens (TAA) and reflect specific anti-tumor immunity.This short term (4 h) ⁵¹Cr-LAI assay provides reproducible and specific results analogous to those using tube-LAI assay. The test has the advantages of being accurate, sensitive and free from technical bias.