Diagnostic Elisa for Parietal Cell Autoantibody Using Tomato Lectin-Purified Gastric H+/K+-Atpase (Proton Pump)

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Abstract
Circulating parietal cell auto antibodies, a useful diagnostic marker for autoimmune gastritis and pernicious anaemia, are currently routinely tested by serum immune of luorescence reactivity with frozen sections of rodent stomach. The major molecular targets of these parietal cell autoantibodies have recently been demonstrated to be the α- and the β-subunits of the gastric H+/K+-ATPase (proton pump)1,2. We have demonstrated that tomato lectin binds specifically to the β-subunit of the proton pump and concomitantly co-purifies the α-subunit3 4. In the present study, we have exploited the latter observation for the development of a diagnostic ELISA for the detection of parietal cell autoantibodies and compared the performance of this assay with an ELISA using crude gastric membranes. The ELISAs were tested on 72 parietal cell autoantibody-positive sera, 72 parietal cell autoantibody-negative sera and 72 disease-control sera. The ELISA using lectin-purified canine proton pump was superior to that using crude canine gastric membranes in that it was about two-fold more sensitive (82% vs. 43%). With an assay sensitivity of 82% and a specificity of 90%, we propose that the ELISA using the lectin-purified proton pump is a rapid, simple, sensitive and specific diagnostic immunoassay for parietal cell autoantibodies.