A computerized in vitro tube leukocyte adherence inhibi tion (LAI) assay indicated that the peripheral blood leuko cytes of patients with cancer of the colorectum, stomach, pancreas, breast, and lung expressed tumor-specific im munity to an organ-type specific neoantigen. In this assay, the peripheral blood leukocytes are incubated with two unrelated extracts of cancer. At the completion of the assay, the nonadherent cells are enumerated electronically by image analysis, and the difference in

more »

... ripheral blood leukocyte nonadherence to the two tumor extracts is used to detect a tumor-specific immune response of the host. The computerized assay is rapid, noninvasive, reproduci ble, and accurate. Tumor-specific immunity is detected in the systemic circulation of most patients who harbor micro foci of cancer. in contrast, fewer patients have a positive LAI response as the stage of the cancer increases. Less than 1% of the more than 400 control subjects had a positive assay. However, about 10% of patients with either colon adenomas or benign mammary dysplasia showed a positive LAI response, and studies of the LAI response of these patients indicated that their lesions expressed an organ type-specific neoantigen. About the third to fourth month after excision of the primary cancer, LAI activity disappeared except in patients who had a moderate amount of residual cancer. Patients who harbored micrometastasis also lost their LAI activity 3 to 4 months after surgery, but the LAI activity returned some months before clinical recur rence; later, LAI activity was abrogated by organ-specific antigen shed from the growing cancer. The results of the computerized tube LAI assay are sufficiently encouraging to warrant studies to determine its efficacy for the diagnosis of human cancer.