Stimulation of the B Cell Receptor, CD86 (B7-2), and the β2-Adrenergic Receptor Intrinsically Modulates the Level of IgG1 and IgE Produced per B Cell

Abstract

Our findings using B cells from either wild-type, CD86-deficient, or β2-adrenergic receptor (β2AR)-deficient mice suggest three mechanisms by which the level of IgG1 and IgE production can be increased on a per cell basis. Trinitrophenyl-specific B cells enriched from unimmunized mouse spleens were pre-exposed to Ag and/or the β2AR ligand terbutaline for 24 h before being activated by either a β2AR-negative Th2 cell clone or CD40 ligand/Sf9 cells and IL-4 in the presence or absence of an anti-CD86 Ab. Data suggest that the first mechanism involves a B cell receptor (BCR)-dependent up-regulation of CD86 expression that, when CD86 is stimulated, increases the amount of IgG1 and IgE produced in comparison to unstimulated cells. The second mechanism involves a BCR- and β2AR-dependent up-regulation of CD86 to a level higher than that induced by stimulation of either receptor alone that, when CD86 is stimulated, further increases the amount of IgG1 and IgE produced. The third mechanism is BCR-independent and involves a β2AR-dependent increase in the ability of a B cell to respond to IL-4. Flow cytometric and limiting dilution analyses suggest that the increase in IgG1 and IgE occurs independently from the isotype switching event. These findings suggest that the BCR, the β2AR, and CD86 are involved in regulating IL-4-dependent IgG1 and IgE production.

Selective Regulation of Mature IgG1 Transcription by CD86 and β2-Adrenergic Receptor Stimulation

“…In addition, full activation of these cells requires the binding of costimulatory molecules expressed on one cell to costimulatory molecules expressed on the other (3,4). One such costimulatory molecule is CD86 (B7-2), which is expressed at a low level on a resting B cell (5,6), but is up-regulated following the stimulation of BCR (7,8), CD40 (9,10), MHC class II (11), LPS receptor (5,7,12,13), IL-4R (14,15), and/or ␤ 2 -adrenergic receptor (␤ 2 AR) (16,17). CD86 binds to the costimulatory molecule CD28 on the Th cell to increase the expression of the costimulatory molecule CD40 ligand (CD40L) on the Th cell and also to increase the level of cytokine produced by the Th cell (13,15,18).…”

“…Although these findings were attributed to a lack of CD28 costimulation on the Th2 cell that resulted in a decrease in the level of IL-4 and CD40L costimulation provided to the B cell, these findings also suggested that CD86 costimulation might generate a signal within the B cell to regulate the level of a Th celldependent Ab response. Recent in vitro data show that the stimulation of CD86 on a B cell activated through CD40 and the IL-4R with or without BCR stimulation increases the level of IgG1 and IgE produced (16,25) and differentially affects the level of antiapoptotic and proapoptotic molecules expressed (26). Likewise, both host and donor B cells from chimeric mice that received donor cells from CD80/CD86-deficient mice and were challenged with a protein Ag were able to produce Ag-specific IgG1, but the level of IgG1 produced by the CD80/CD86-deficient cells was decreased compared with that of the host B cells (27).…”

“…Likewise, stimulation of the ␤ 2 AR on a B cell, which serves as the receptor for the neurotransmitter norepinephrine that is released in the B cell microenvironment within lymphoid organs (28), increases the level of CD86 expressed on and IgG1 produced by a B cell activated in vitro in the presence of a Th2 cell or CD40L/IL-4 (16). Since the Th2 cell did not express ␤ 2 AR, it was concluded that stimulation of ␤ 2 AR on a B cell most likely had a direct effect on IgG1 production.…”

“…Supernatant was frozen immediately at Ϫ80°C until analyzed by ELISA, as described in detail previously (16). A standard curve for IgG1 was prepared using known quantities of the myeloma protein MOPC-21 (IgG1; Sigma-Aldrich).…”

“…The number of IgG1-positive B cells was determined by FACS analysis, as described in detail previously (16). Briefly, B cells were collected on day 6 after initial activation and stained with PE-conjugated rat anti-mouse B220 Ab (clone RA3-6B2; BD PharMingen) and FITC-conjugated rat antimouse IgG1 Ab (clone A85-1; BD PharMingen).…”