Cellular and molecular mechanisms of regulation of autoantibody production in lupus

Abstract

The hyperactive interaction between helper T cells and autoimmune B cells in individuals predisposed to systemic lupus erythematosus (SLE) can be interrupted by induction of regulatory and suppressor T cells. Using two strategies-high dose tolerance to an immunoglobulin-derived peptide, and minigene vaccination with DNA encoding T cell epitopes presented by MHC class I molecules-our group has induced at least three types of regulatory/suppressive T cells. They include CD8+ T cells that suppress helper T cells by cytokine secretion, CD8+ T suppressors that kill B cells making anti-DNA antibodies, and peptide-binding CD4+CD25+ regulatory T cells that suppress B cells by direct cell contact. Each of these lymphocyte subsets suppresses anti-DNA antibody production and delays the onset of nephritis in BWF1 lupus-prone mice. Patients with SLE have amino acid sequences similar to those from murine anti-DNA antibodies used in these studies, and at similar locations in the VH regions of anti-DNA immunoglobulins. Therefore, strategies described here might ultimately be useful in therapy of the human disease.

FIGURE 1

CD4⁺CD25⁺ regulatory T cells from tolerized NZB/NZW F1 mice suppress the ability of syngeneic B cells to synthesize IgG anti-DNA antibody in vitro, and that suppression depends upon membrane-associated TGF and/or GITR. 1 × 10⁵ B cells from spleens of unmanipulated old BWF1 females were cocultured with 1 × 10⁶ CD4⁺ splenic helper T cells from naive young mice and 1 × 10⁶ pCONS-binding CD4⁺CD25⁺ spleen cells from young BWF1 mice tolerized with 1 mg pCONS i.v. one week prior to harvest. Various cell combinations are shown on the x-axis, as well as inhibition with anti-GITR or anti-TGF-β-LAP antibody. Antibody-forming cells (AFC) per 10⁶ B cells are shown on the y-axis. Information below the graphic indicates the contents of cultures labeled a, b, c, d, e. CD4⁺CD25⁺ T cells were selected by binding with a soluble dimer of I-Ed and pCONS. Note that in c, AFC formation is suppressed compared with b (P < 0.0004), and the suppression is abolished by inhibiting either GITR (d) or TGF-lap (e). Addition of CTLA4-Ig to the culture to inhibit surface CTLA4 on Tr cells did not inhibit suppression (data not shown). Statistical analysis by ANOVA showed that the following comparisons were significantly different at P < 0.0004: a vs. b, a vs. c, b vs. c, c vs. d, c vs. e.

FIGURE 2

CD8⁺ T cells from BWF1 mice tolerized with 1 mg pCONS suppress anti-DNA antibody production by syngeneic B cells. Data shown are representative of four experiments. Cultures contain 1 × 10⁵ B cells from spleens of unmanipulated old BWF1 females, and pCONS. CD4⁺ T cells are from unmanipulated young BWF1 mice and give help for the B cell production of anti-DNA antibody (b). To CD4⁺ B are added CD8⁺ cells from unmanipulated young syngeneic mice (c), or CD8⁺ cells harvested from spleens one week after administration of pCONS (d). CD8 to CD4 ratios are 1:1. Note that the tolerized CD8⁺ T cells suppress anti-DNA antibody production 10-fold (compare d vs. b).