Generation of High‐Rate Ovalbumin‐Specific Antibody‐Secreting Cells in Cultures of Human Peripheral Blood B Cells Obtained from Non‐Immunized Blood Donors

When human peripheral him id B cells are cultured for 6 days with the T cell‐dependent peptide antigen ovalbumin (OA) in the presence of antigen‐presenting cells and helper T cells, plaque‐forming cells (PFC) are generated. These OA‐induced PFC differ from the conventional high‐rate antibody‐secreting PFC formed after stimulation of B cells with recall antigens (e.g. tetanus toxoid) in that they secrete antibody at a very low level. Previous studies have shown that OA‐induced PFC are B lymphocytes in an early activation stale rather than cells that have differentiated into plasmablasts. The apparent arrest in the maturation of OA‐induced PFC in an early activation phase can he overcome by simultaneous stimulation with interleukin 2 (1L‐2) and gamma interferon (IFN‐γ). The isotype of the OA‐specific antibodies secreted, however, are only of the IgM class, demonstrating that an isotype switch docs not occur.