Antibodies with differing molecular sizes in mice.

The antibody responses of CH mice to haemocyanin, pneumococcal polysaccharide (SSS III) and sheep erythrocytes were studied after a single intravenous administration. Serum antibody against each antigen was present on the fifth, but not on the third day. Antibodies against haemocyanin and against SSS III migrated electrophoretically as γ globulins and had the ultracentrifugal sedimentation properties of 6.5S globulins. Sheep erythrocyte haemolysins were largely γ macroglobulins which sedimented in the ultracentrifuge in the manner of 18S globulins. A small proportion of haemolysin activity was found among the 6.5S γ globulins.