In vitro synthesis of IgE by human peripheral blood leucocytes. III. Release of pre-formed antibody.

The appearance of IgE in supernatant fluids from cultures of human peripheral blood leucocytes (PBL) is employed in many laboratories as an index of antibody 'synthesis'. This study demonstrates that, unlike IgG, the majority of cell associated IgE is sequestered by PBL in a tightly bound form, which resists extraction via the freeze-thawing (F/T) techniques in current use. A method is presented for the quantitative extraction of cell associated IgE, involving brief acid treatment of whole cells, and is shown to yield up to 100% more IgE than the F/T procedure. The use of this extraction process on PBL before and after culture permits discrimination between release of pre-formed IgE and de novo synthesis, both of which are demonstrated to occur to widely differing degrees in PBL cultures from different donors.