Characteristics of the leucocyte-aggregation assay for cell-mediated immunity.

The leucocyte aggregation assay detects cell-mediated immunity by the specific adherence of sensitized lymphocytes onto target cell monolayers. Leucocyte aggregates appear to develop by instruction of non-immune cells by sensitized T lymphocytes. B cells may function in a secondary capacity to amplify aggregate formation. The reactions are sensitive to low temperatures and to metabolic inhibitors of protein and RNA synthesis and function. Serum factors alternatively enhanced or blocked the phenomenon, depending upon the immune status of the patient. This assay may prove useful for the dissection of allograft rejection and tumor resistance due to its brevity, reflection of T-cell immunity, and sensitivity to host humoral factors.