Demonstration that IgG memory is carried by IgG-bearing cells

Memory B cells which give rise to IgG antibody-producing cells were generally assumed to be IgG-bearing cells. However, recent studies indicating that very few IgG-bearing cells exist in lymphoid tissue brought this assumption into question. In this study, we examined directly the question whether IgG-bearing cells contain functional precursors of IgG antibody-producing cells. Using the adoptive secondary immune response, we demonstrated that Ig-1 b-bearing cells, isolated with the fluorescence-activated cell sorter (FACS), are the functional precursors of Ig- 1 b-producing cells. Further, we have enriched IgG2 and IgG1 memory B cells using the FACS. The results show that IgG2-bearing cells are the functional precursors of the IgG2 antibody-producing cells. Likewise, the IgG1-bearing cells are the functional precursors of IgG1 antibody-producing cells. Thus, IgG memory cells have surface IgG which indicates the class and allotype commitment of the memory cell and its progeny antibody-forming cells.