Alteration of antibody specificity during isolation and storage.

Isolation buffer characteristics and storage conditions could partially transform natural antibodies. 50 IgG factions were isolated from seven healthy donors' sera using various protein G columns and buffers. PAGE revealed no major antibody cleavages; purity of IgGs eluted at pH 2.4-3.5 was close to homogeneity, independent of buffer composition. Although eluting at pH 2.4 resulted in 3.5- or 17-fold higher antibody yield compared to pH 3.0 or 3.5, respectively, it distorted the antibody molecule. IgGs eluted at pH 2.4 acquired reactivity against diagnostically important autoantigens, confirmed by standardized ELISAs. Preserved antibodies' natural activity is important in further experiments with oxidatively-induced autoantibodies.