Activation of murine B lymphocytes by anti-immunoglobulin is an inductive signal leading to immunoglobulin secretion.

Abstract

Cultures of isolated mouse splenic B lymphocytes activated by the divalent F(ab')2 fragment of purified rabbit anti-mouse Fab or class-specific anti-mouse IgM antibodies can be driven on to high rate Ig secretion by the addition of the supernatant fluid of a 24-h culture of concanavalin A-activated spleen cells (SN). The polyclonal antibody response to anti-Ig pus SN is comparable in magnitude with the lipopolysaccharide response as measured in a reverse plaque assay. The addition of SN can be delayed for 24 h after addition of anti-Ig without changing the kinetics of the response. Addition at 48 h delays the response by 24 h. The response to F(ab')2 anti-Fab plus SN is sensitive to Fc-dependent inhibition because intact anti-Fab antibodies inhibit strongly at relatively low concentrations. The monovalent Fab' fragment fails to induce Ig secretion, indicating that cross-linkage of surface immunoglobulin is required. Although the production of active SN is T cell dependent, the response to anti-Ig plus SN is T independent. These findings are interpreted as a polyclonal model of a thymus-dependent antibody response. X

Deficient TACI Expression on B Lymphocytes of Newborn Mice Leads to Defective Ig Secretion in Response to BAFF or APRIL

“…Anti-IgM stimulation not only results in proliferation of B lymphocytes and secretion of Igs with the help of cytokines such as IL-4, but also stimulates TACI expression (35,36). Thus, BCRmediated up-regulation of TACI expression may be instrumental in the production of Ab response against TI-II Ags.…”

“…Multivalent Ag-mediated activation of B lymphocytes can be mimicked in in vitro assays by using F(abЈ) 2 anti-IgM Abs (35,36). In newborns, however, the anti-IgM mediated signal typically induces apoptosis in B lymphocytes (37,38) unless a second signal, such as LPS or T lymphocyte cytokines are added to culture medium (39 -41).…”

Proliferation and Differentiation Requirements for the Induction of Two Retroviral Loci during B-Cell Activation

“…:~ Cultures contained 50~ conditioned medium from 24 h Con A-stimulated lymphocytes cultured at 107 cells/ml. dependent on the addition of T-cell factors, supplied by supernatants of Con A-stimulated spleen cells (Parker et al, 1980). We tested several F(ab')2 preparations of rabbit anti-mouse IgM for mitogenicity and selected the most active for further study.…”

“…In some experiments BUdR, hydroxyurea, thymidine or deoxycytidine (all from Calbiochem) was added to the cultures at times and concentrations described below. Lymphocytes at 2 x 105 cells/ml culture medium containing 2 × 10 -5 M-2-mercaptoethanol were also stimulated with mitogenic F(ab')2 preparations of rabbit anti-mouse IgM sera plus supernatants from 24 h cultured Con A-stimulated spleen cells prepared as described by Parker et al (1980). Rabbit anti-mouse IgM sera were obtained from rabbits hyperimmunized with MOPC 104E protein emulsified in complete Freund's adjuvant.…”

“…Rabbit anti-mouse IgM sera were obtained from rabbits hyperimmunized with MOPC 104E protein emulsified in complete Freund's adjuvant. F(ab')2 fractions were prepared by affinity purification of IgG on Protein A-Sepharose, pepsin digestion and G-100 chromatography (Parker et al, 1980). Spleen cells were routinely cultured for 3 days before quantifying virus induction and B-cell differentiation.…”