Low affinity antibody to rubella antigen in patients after rubella infection in utero.

As a measure of the affinity of antirubella antibody, the resistance of the antibody to elution was used by increasing concentration of ammonium thiocyanate. The term affinity index has been used to define the molarity of thiocyanate which leads to a reduction of 50% of the initial density. The serum from a group of patients with intrauterine rubella was compared with the serum from a group of deaf children, some of whom could have rubella, and a group of controls with antibody following natural infection. The results show that the affinity index of patients with rubella is significantly lower than that of controls. The other deaf patients span the range of indices of the rubella and control groups suggesting that a number of those children could have deafness caused by intrauterine rubella.