Search

Covalently linked subunits, subunits aggregated from two half subunits, half subunits, F(ab'μ)2 and Fab'μ were prepared. K-values 1900-5800 times lower than those for intact IgM and rabbit red cells were found for the covalently linked subunits, the aggregated subunits, and F(ab'μ)2, and 12,500-38,500 times lower for half subunits and F(ab'μ)2. Only whole subunits and F(ab'μ)2 agglutinated rabbit red cells; compared to intact IgM the titre was reduced markedly, but from the calculated amount of molecules bound per red cell, IgM was found to be on a weight basis only twice as effective as the subunits and F(ab'μ)2 in agglutinating the cells. [ABSTRACT FROM AUTHOR]

Rabbit red cells were found to bind a maximum of 1.8 X 105 IgM anti-I-molecules. A K-value of 5.0 ± 0.8 X 108 I/M was determined for the reaction between the cells and intact anti-1 at 5 °C; the K-value was little affected by changes in temperature. Hybrid 17S and 8S molecules composed of varying amounts of cold agglutinin and inactive IgM were prepared by reduction with 2-mercaptoethanol and reassociation. The results obtained with the reassociated products indicate random reassociation at the half subunit level. It is concluded that a 17S fraction with four or more active half subunits shows binding similar to intact IgM, while 8S fractions with two active half subunits show binding similar to the cysteine-reduced 8S IgM. [ABSTRACT FROM AUTHOR]

A mixture of rabbit IgM anti-human A1 red cell antibody and a human 125I-labelled monoclonal IgM was reduced with mercaptoethanot and exposed to oxygen under conditions in which most of the half subunits coalesced to IgM subunits with reformation of interchain disulphide bonds. Hybrid molecules were demonstrated in the mixture by precipitin tests with autoradiography and by binding of 125I to human A1 red cells. By careful selection of IgM antibodies with high energy in each binding site, such hybrids may be useful 'IgM coats' for haemagglutination inhibition tests attempting to define subclass- specific and genetically determined antigens on IgM. [ABSTRACT FROM AUTHOR]