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Purification of antibodies to membrane antigens of hamster cells transformed by sv40 and binding of the radioiodinated, purified antibodies to intact cells

Antisera to membrane antigens of SV40‐transformed hamster kidney cells were prepared by injecting a membrane fraction of HK7 cells into rabbits. Purified antibodies were prepared by adsorption of the IgG fraction of the antisera onto, and by elation from, living or glutaraldehyde (GA) fixed HK7 cells. Purification from GA‐treated cells yielded highly satisfactory purified antibody preparations, the reactivity of which could be demonstrated in fluorescent antibody tests. These preparations were radioiodinated with 125I to a specific activity of the order of 10μc/μg and their activity was assayed by ability to bind to living HK7 cells. The labelled antibodies maintained their binding ability practically unchanged for at least 6 months. They could be further purified by an additional adsorption‐elution cycle, using living cells. The doubly purified, radioiodinated antibodies, had a high affinity for HK7 cell membranes: 43% of the radioactivity became bound when 0.3 ng eluate was reacted with 1 × 106 cells, as compared to 8% bound to normal kidney cells.