Specific anti-erythrocyte focus formation as a measure of autoantibody secreting cells in NZB mice.

Using a modification of the antibody forming cell (AFC) focus assay, it is possible to quantitate the spontaneous anti-erythrocyte autoantibody response of New Zealand Black (NZB) mice at the level of the autoantibody secreting cell. This complement independent assay is specific for an antigen(s) present on unmodified mouse erythrocytes. A comparison with the direct Coombs' test showed that the focus assay detected autoantibody responses earlier and demonstrated a wide range of AFC levels in responding mice. The focus assay provides a method for evaluating autoimmunity at the cellular level and for investigating the activities of cells responding to autoantigens.