Kinetics of antibody production by single cells. I. Automatic recording of plaque production in the local haemolysis system.

The primary antibody response of the IgM type against sheep red blood cells, by spleen cells obtained from mice immunized has been studied at the cellular level. The modified plaque assay technique which was used allows the quantitative recording of plaque formation and growth in a carboxymethylcellulose gel. The distribution of plaque size at different times of incubation indicates that the secretion rate and the final amount of antibody released differ considerably between individual PFC of the same splenic population. However, the mean sizes of plaques from splenic populations at the same time after immunization are similar from mouse to mouse. During incubation, the kinetics of plaque growth display characteristic features, thus differentiating PFC populations from mice examined at different times after immunization. Most notably, there is a decrease in the mean size of the plaques between day 4 and day 5 following immunization. These results are discussed in terms of antibody secretion by PFC populations during the primary response.