Switch in immunoglobulin class production observed in single clones of committed lymphocytes.

Mouse spleen cells, after stimulation with lipopolysaccharide, were cloned in culture. After 4 to 5 days, the daughter cells were stained and examined for immunoglobulin class with double immunofluorescent reagents. A switch of the stained color of these cells was observed, implying a switch from imunoglobulin M to immunoglobulin G production in the progeny of a single B cell.