Effect of B‐cell receptor engagement on CD40‐stimulated B cells

Abstract

SUMMARYActivation of human B cells in vitro either by cross-linking of surface immunoglobulins (sIg) or by triggering CD40 antigen, in the presence of interleukin-10 (IL-10) and interleukin-2 (IL-2), may result in high levels of immunoglobulin secretion in vitro. We studied the combined effects of ligation of the B-cell receptor (BCR) and CD40 [with anti-CD40 monoclonal antibody (mAb)] on B-cell proliferation and production of human immunoglobulin. For this purpose highly purified splenic B cells were cultured with various combinations of anti-CD40 and IL-10/IL-2 or IL-4 in the presence of CD32-transfected L cells. Simultaneous cross-linking of the BCR was achieved by mAb held on CD32-L cells or Staphylococcus aureus (SA). We found that dual BCR and CD40 ligation with IL-10/IL-2 leads to reduced immunoglobulin G (IgG) secretion compared with B cells stimulated with either anti-CD40 and IL-10/IL-2, or compared with B cells stimulated with SA or anti-BCR mAb and IL-10/IL-2. Dual BCR and CD40 ligation with anti-immunoglobulin mAb (anti-k+anti-l light chains) but not with SA induced a similar reduction in IgM production. The reduced immunoglobulin secretion found during dual ligation is accompanied by increased proliferation. This was independent of cytokine stimulation but SA/CD40-induced proliferation was increased in the presence of IL-10/IL-2, although not with IL-4. The combination anti-k and anti-l with anti-CD40 showed a long-term suppression of IgG and IgM production (at least 14 days), while anti-k or anti-l alone, or SA, allowed a moderate recovery of immunoglobulin production by day 14. These results suggest that simultaneous B-cell antigen receptor cross-linking and CD40 engagement via CD40L on T cells induces strong initial proliferation. This may be followed later by antibody production depending on the strength of the BCR signal and the presence of the appropriate cytokines.

Activated Human B Lymphocytes Express Cyclooxygenase-2 and Cyclooxygenase Inhibitors Attenuate Antibody Production

“…Following exposure to CD40L plus anti-IgM Ab (or pansorbin) for 7 days, B lymphocytes become activated, proliferate, and differentiate, thus increasing their production of IgM and IgG (20). Our findings of drastically reduced IgM and IgG levels following incubation with indomethacin or the selective Cox-2 inhibitor SC-58125 supports the concept that the B cell Cox-2-derived products are required for optimal Ab production.…”

“…Pharmacological doses of these drugs that have been previously shown to block PG production range from 5 to 40 M (9, 10). Dose response experiments (1,5,10,20,40, and 80 ⌴) were conducted to determine the optimal dose for PG inhibition using the supplier's protocol for the PG screening kit (Cayman Chemical).…”

Cross-Linking Surface Ig Delays CD40 Ligand- and IL-4-Induced B Cell Ig Class Switching and Reveals Evidence for Independent Regulation of B Cell Proliferation and Differentiation

“…The varied effects of the different anti-Ig mAbs on cell division suggested that these reagents might differ qualitatively in their ability to signal via sIg. Different mitogenic properties of various anti-Ig reagents have been noted previously and attributed to qualitatively different signals delivered to the B cell as a result of different sIg cross-linking capacities (18,(51)(52)(53), their binding of different sIg epitopes (53,54), or coligation of Fc␥RIIb (55,56). This latter possibility was eliminated in this study by the inclusion of an antiFc␥RIIb mAb in selected experiments.…”

Incorporation of Glycosylphosphatidylinositol-Anchored Granulocyte- MacrophageColony-Stimulating Factor or CD40 Ligand Enhances Immunogenicity of Chimeric Simian Immunodeficiency Virus-Like Particles

“…It is known that cytokines play a critical role in immunoglobulin class switching. Schilizzi et al have shown that simultaneous B-cell antigen receptor cross-linking along with CD40 engagement in the presence of IL-10 or IL-4 reduced IgG secretion in vitro (43). Thus, the decreased IgMto-IgG switch could presumably be explained by the high levels of IL-4 and IL-10 induced by CD40L SIV VLPs combined with CD40-CD40L interactions.…”