Certain Polyclonal Antinuclear Antibodies Cross‐React with the Surface Membrane of Human Lymphocytes and Granulocytes

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Abstract
Five out of 24 human sera with antinuclear antibody (ANA) titers of 1250 or more contained ANA that bound in vitro to normal viable human mononuclear blood cells and granulocytes, but not to erythrocytes. The antibodies can be eluted off from the cell membranes and shown to possess ANA activity. Anti-native DNA antibodies and lupus erythematosus factor were not recovered in eluates, indicating that they did not react with the cells. The cells absorbed 75%–87% of the ANA activity from three sera. ANA reacted with both T-lymphocyte-depleted and -enriched mononuclear cells. No or minimal amounts of ANA bound to mouse spleen cells in suspension; in contrast, the ANA eluted from human cells reacted with nuclei of smeared mouse spleen cells. The cross-reacting antibodies were predominantly IgG that bound well at 37°C, and F(ab')2 fragments carried both activities. The ANA-binding plasma membrane antigen was resistant to trypsin and RNAse but was completely inactivated by glutaraldehyde. The data indicate that human leukocyte plasma membranes and cell nuclei from many species contain a cross-specific antigen. Alternatively, the antigen may be produced in the nucleus and somehow attach to the plasma membrane.