The use of [125I]C1q subcomponent for the measurement of complement binding antibodies on cell surfaces.

An assay using 125I-labelled human C1q has been developed for the measurement of complement fixing antibodies bound to cell monolayers or cell suspensions. The method has been adapted for use either during or after sensitisation of the cells with antiserum, is simple to perform and does not require require prelabelling of the target cells.