IMMUNOCHEMICAL STUDIES ON RED-CELL AUTO ANTIGENS - USE AND LIMITS OF IMMUNOPRECIPITATION FROM BIOTINYLATED ERYTHROCYTE-MEMBRANE

Erythrocyte surface was labelled by means of biotin; immunoprecipitati on technique was then used to localise antigens recognised on red cell membrane proteins by: a) autoantibodies from 13 patients with antiery throcyte autoimmunity; b) commercially available anti-D and anti-k (Ce llano) antierythrocyte alloantibodies. Results with alloantibodies are comparable to those obtained using radiochemical probes. Immunoprecip itations with autoantibody containing eluates showed reactivity at dif ferent molecular weights (the most common at 34-50 kD, others at 100 a nd 45 kD and a newly described one at 80 kD), thus confirming that man y membrane proteins may act as target antigens for erythrocyte autoimm unity. We found a higher percentage of reactive immunoprecipitates tha n previously reported using the same labelling method. However, critic al conditions to allow valuable results seem to be a threshold amount of autoantibody to precipitate any recognisable band and the sensitivi ty of the detection method. Hence methodological variables must be tak en into consideration before concluding that ''non protein'' antigens trigger the autoimmune process.