Correlations between immunoglobulin- and antibody-synthesizing cells during primary and secondary immune responses of rats immunized with peroxidase.

The development of cells synthesizing immunoglobulins without detectable antibody activity and of antibody-synthesizing cells was studied during primary and secondary immune responses of rats immunized with horseradish peroxidase. After primary immunization with peroxidase emulsified in Freund's complete or incomplete adjuvant, the first antibody-producing cells appeared 4 days after injection. They were preceded by cells synthesizing IgG and IgM without antibody function, appearing 3 days after giving antigen. The ratio between the latter and the former population of cells regularly decreased during the primary response. Seventy to 100 per cent of cells synthesizing immunoglobulins without antibody activity were induced by the antigen, the remainder being induced by the adjuvant. In both populations, the positive cells were always immature or mature plasmocytes. At various times after primary injection, animals received a booster inoculation of soluble peroxidase or of peroxidase emulsified in Freund's adjuvant. Antibody-producing cells, in early stages of differentiation, appeared between 2 and 3 days after challenge and were not preceded by cells synthesizing immunoglobulins without antibody function. These latter cells were reduced or absent after secondary challenge. Increasing the sensitivity of detection of active sites of antibodies, by using direct methods of staining with fixed or unfixed cells gave no increase of antibody-producing cells.