The Spontaneous Induction of Anamnestic Antibody Synthesis in Lymph Node Cell Cultures Many Months after Primary Immunization

An in vitro model system was developed in which interactions between persisting antigen, humoral antibody, and the various lymphoid cells involved in the immune response may be analyzed. In this system IgG antibody synthesis was spontaneously induced—no extrinsic antigen required—simply by transferring lymphoid cells from a human serum albumin (HSA) immunized rabbit into cell culture. Vigorous spontaneous antibody responses were obtained in cell cultures from 1 month up to a year after immunizing with 1 mg of polymerized-HSA. Induction of the spontaneous antibody response requires a 2- to 3-day period in vitro. The quantity of antibody synthesized per day, for a 3-day period after induction, was as high as 1000 times the amount obtained on the 1st day of culture. Addition of specific antibody to cultures inhibited the inductive but not the synthetic phase of the response. Addition of microgram quantities of antigen inhibited spontaneous induction, whereas nanogram quantities inhibited in some experiments and induced additional antibody synthesis in others. Initiation of the spontaneous in vitro response was attributed to cell-associated persisting antigen, whose activity is subject to an antibody feedback mechanism.