Non-identical reaction of undissociated HCG and HCG-beta subunit with anti-HCGbeta serum.

Based on gel-filtration experiments, estimates of the content are given of undissociated human chorionic gonadotrophin (HCG) and HCG-beta subunit in HCG preparations. Radioimmunoassay of three HCG preparation using an antiserum against HCG-beta subunit showed that the slope of displacement curves was dependent on the ratio of HCG-beta subunit to undissociated HCG, the slope being steeper (negative) with increasing ratio. The implication of this observation on the choice of a suitable standard for HCG-beta radioimmunoassay is discussed.