Immunoglobulin-producing cells in cultured human peripheral blood lymphocytes: Modulation by accessory cells and enhancing effect of polyacrylamide beads

Abstract

In a reverse hemolytic plaque assay performed with sheep red blood cells coated either with purified antibodies polyvalent for human immunoglobulins (Ig) (anti-F(ab′) 2) or monospecific for γ chains, or with protein A, we detected few reverse plaque-forming cells (PFC) among fresh human peripheral blood lymphocytes (PBL). Upon culture, the numbers of reverse PFC remained stable during the first 4 days and then increased up to 1000–10,000 PFC 10 6 cells on Days 5–7. This phenomenon required cell proliferation and was associated with some degree of B-cell differentiation as shown by immunofluorescent study of surface and cytoplasmic Ig. Trinitrophenyl-polyacrylamide beads (TNP-PAA) and unsubstituted polyacrylamide beads significantly enhanced the numbers of reverse PFC in cultured PBL. The optimal enhancement of reverse PFC required the same experimental conditions that the induction of a specific anti-TNP PFC response by TNP-PAA required: a supportive batch of fetal bovine serum, monocytes (which could be replaced by 2-mercaptoethanol), and T cells. The latter acted in the inductive phase and was apparently not required for Ig secretion by cultured cells in our assay.