The goal for the proposal is to develop an assay of cell-mediated immunity in breast cancer with clinical applicability, i.e., prognosis, guide to therapy and diagnosis. The rationale for the proposal is: 1) Improvement of leukocyte adherence inhibition assay, 2) utilization of highly purified TAA which should result in greater specificity in the leukocyte adherence inhibition assay (LAI), 3) parallel use of normal tissue antigen from same patient as control, 4) the use of sensitized frozen lymphocyte (allogeneic) because of easy accessibility of large quantities, access to repetitive determinations at convenience, and easy application of blocking assay, 5) in addition, basic understanding of the mode of action of LAI, i.e., cellular participation, lymphokine study, interplay of blocking factor, will lead to an improved assay. To accomplish this goal, studies will be performed in two categories of patients. A vertical study (patients to be entered during first two years) includes patients with benign and malignant disease, to seek comparative efficiency of LAI utilizing fresh PBL vs. frozen lymphocytes. A horizontal study (1st, 2nd and 3rd year) will evaluate patients at 1, 3 and more than 5 years post-mastectomy with no evidence of disease, as well as all patients at point of recurrent disease. All patients will undergo LAI and blocking assays at 3 month intervals as follow-up to therapy. An improved CMI assay to monitor breast cancer patients will materialize at the end of 3 years.