Autologous red blood cells potentiate antibody synthesis by unfractionated human mononuclear cell cultures

We have tried to determine the most favourable conditions for the in vitro induction of specific antibody (Ab) responses to tetanus toxoid (TT) and keyhole limpet haemocyanin (KLH). Human peripheral blood mononuclear cells (PBMNC) were obtained from normal volunteers and stimulated with PWM, TT, KLH, and mixtures of PWM and antigens in the presence or absence of autologous red blood cells (RBC) (1:50 ratio of PBMNC/RBC). The cultures were harvested on day 11; immunoglobulins were determined immunonephelometrically and Ab levels by ELISA with human antibodies used for calibration. While anti-TT responses were easy to induce with PBMNC from recently boosted individuals, the production of anti-TT from PBMNC obtained from non-recently boosted individuals was only possible when PBMNC were stimulated with TT and PWM in the presence of autologous RBC. Similarly, anti-KLH responses were easier to induce with PBMNC from an immune donor; maximal response was observed after stimulation with PWM + KLH in the presence of autologous RBC. Stimulation of primary anti-KLH responses with PBMNC from non-immune donors was only successful when the cells were stimulated with KLH + PWM in the presence of autologous RBC. The potentiation of human B-cell responses with autologous RBC can be abrogated by pretreatment of PBMNC with anti-CD2 antibodies and is associated with increased expression of IL-2 receptors and increased production of gamma interferon (IFN-gamma). However, addition of IFN-gamma in different doses and at different times to PWM-stimulated PBMNC cultures was not as effective as addition of RBC in enhancing the production of immunoglobulin and antibody.