The reactivity of subunits of IgM anti-B

Abstract

The reactivity of native IgM anti-B and of the monomer subunits with B cells was investigated using ¹²⁵I-labelled antibody. A proportion of the monomers produced by mercaptoethanol treatment retained antibody activity, but the value of the equilibrium constant of the subunits was reduced by a factor of 36–170 compared to that of the native IgM molecule. It is concluded that native IgM anti-B is attached to red cells by at least two combining sites and evidence is given which indicates that IgM anti-A behaves similarly.