Effect of substrate on indirect immunofluorescence tests for intercellular and basement membrane zone antibodies.

The effect of substrate on the result of indirect immunofluorescence tests for intercellular and basement membrane zone antibodies was examined by testing concurrently 288 human sera on the three substrates used most commonly for this test, that is, monkey and guinea pig esophagus and normal human skin. Seventy-five sera had intercellular antibodies and 56 had basement membrane zone antibodies. The substrate influenced the results of 41% of assays for intercellular and 56% of those for basement membrane zone antibodies. Thirty-one percent of intercellular and 38% of basement membrane zone antibodies failed to react to one or more than one substrate, leading to false-negative reactions. In an additional 10% to 12% of sera, the titer of the reaction was influenced by the substrate. These results indicate that the substrate used has a major impact on the result of indirect immunofluorescence tests for antibodies to skin. The best overall single substrate was monkey esophagus, but optimal results were obtained when both monkey and guinea pig esophagus were used.