Clonal analysis of B cells induced to secrete IgG by T cell-derived lymphokine(s).

Abstract

The switch from IgM to IgG (or IgA, IgE) synthesis has been studied in both normal and neoplastic Ig-secreting cells (1-6). Evidence suggests that DNA rearrangements precede isotype switching. The nature of the signals that induce isotype switching are not understood, although T cells (7-13), T cell-derived lymphokines (14)(15)(16)(17)(18)(19)(20), and mitogens (20-22) can influence switching in activated B cells.We have previously (16) described a T cell-derived lymphokine termed "B cell differentiation factor for IgG" (BCDF3,), l that induces increased levels of IgG1 secretion in lipopolysaccharide (LPS)-stimulated splenic B cells. T cell supernatants (SN) containing BCDF3, also contain lymphokines that suppress the secretion of IgG3 (23) and IgG2 (24,25). These changes in IgG secretion are accompanied by corresponding changes in the steady state levels of mRNA for each IgG subclass (23). BCDF3,-containing SN do not act on cells that bear surface IgG (sIgG) at the initiation of culture (16). Furthermore, BCDF7 does not bind to Sepharose-coupled IgM, IgD, or IgG (25). The cell surface receptor for BCDF3,, then, is probably not sIg.The mechanism of action of BCDF3, is unclear. It might induce growth of an sIgG + subset of B cells. Alternatively, BCDF3" might induce sIgG-B cells to secrete IgG1. In the present studies, we have examined the effects of a BCDFTcontaining T cell SN on normal B cells in a limiting dilution culture system. Our results suggest that BCDF3,-containing SN induce IgG1 secretion in a subset of sIgG-B cells already committed to a differentiation pathway leading to IgG1 secretion. These cells do not arise from precursors of IgG3-secreting cells. Materials and MethodsAnimals. We used female C57BL/6 × DBA/2 F~ (BDF1) mice (The Jackson Laboratory, Bar Harbor, ME) 8-16 wk old. Lewis rats (Harlan Sprague Dawley, Inc., Indianapolis, IN), used at 3-6 wk, were a source of thymus cells.

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

“…Previous data indicated that the amount of IgG1 produced by CD40L/IL-4-activated B cells changes because of an increase in the level of class switching to IgG1 and the level of mature IgG1 transcript (19,29). Previous data also indicated that the amount of IgG1 protein produced by CD40L/IL-4-activated B cells is increased further when CD86 (16,26) and/or ␤ 2 AR (16) are costimulated on the B cell.…”

“…In contrast, the mechanism by which CD40 and IL-4R stimulation on a B cell regulates IgG1 production at the level of class switching (19,29) and/or mature IgG1 transcript (30 -32) is well known. The class switching event is regulated by CD40-and IL-4R-induced NF-B and STAT-6 binding to the germline ␥1 promoter, respectively, to activate transcription of germline ␥1 (referred to as intervening ␥1 (I␥1)) (33)(34)(35)(36)(37)(38)(39).…”

“…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). Subsequently, CD40L and the secreted cytokine interact with CD40 and a cytokine receptor on the B cell to activate the process of Ab production and to regulate the process of Ig isotype class switching from IgM to another isotype that is used to mediate specific immune effector functions (19,20).…”

Serological, biochemical, and functional identity of B cell-stimulatory factor 1 and B cell differentiation factor for IgG1.

“…1 legend). It should be noted, however, that the majority of the cells producing IgG1 and IgG3 are different (19). Neither HPLC-purified BSF-1 nor affinity-purified BSF-1 bad any activity in the BCDF-/~ assay ( Fig.…”

H3 trimethyl K9 and H3 acetyl K9 chromatin modifications are associated with class switch recombination

“…The finding that the histones associated with both S␥3 and S␥1 were hyperacetylated with LPS ϩ IL4, whereas switching occurred only to IgG1 (13,14), led us to examine other histone modifications to determine whether some marks would better predict which SR would undergo CSR. Primary naïve splenic murine B cells are cultured either with LPS to stimulate them to switch from IgM to IgG3, or with LPS ϩ IL4 to stimulate them to switch from IgM to IgG1 (18 (19) and continues through 96 h. We selected 72 h to examine chromatin modifications because by then most cells have undergone at least the two divisions required to initiate switching, and CSR is still ongoing in a significant percentage of them (20). Chromatin was prepared from B cells treated with LPS or LPS ϩ IL4 for 72 h and subject to ChIP by using commercial antibodies that specifically recognize various modified histones (see SI Appendix).…”