BAFF and Autoimmune Disease Samia Ragheb, Ph.D. Wayne State University Department of Neurology Department of Immunology & Microbiology

MG is a B-cell Mediated Disease 1. AChR-specific antibodies are present in the serum of 85% of all patients with generalized MG; these antibodies are responsible for the pathology of MG, leading to impaired neuromuscular transmission and subsequent muscle weakness 2. In vitro, lymphocyte cultures from MG patients produce AChR-specific antibodies 3. EAMG can be induced in lab animals; serum anti-AChR antibodies are present in these animals 4. EAMG can be passively transferred, via antibodies, from immune animals to naïve animals and from man to mouse

Overexpression of CXCL13, CD23, and Bcl-2 in the Myasthenic Thymus CXCL13: promotes B-cell migration and homing of B-cells to lymphoid follicles CD23: promotes the survival and differentiation of germinal center B-cells through a mechanism that involves upregulation of Bcl-2 Bcl-2: pro-survival molecule that inhibits apoptosis

BAFF = TNFSF13b Myeloid cells produce and secrete Baff (B-cell activating factor of the tumor necrosis factor superfamily) A membrane-bound form of Baff is also expressed on the surface of myeloid cells; these include monocytes, macrophages, and dendritic cells Baff transgenic animals exhibit hypergammaglobulinemia, lymphoproliferation, and B-cell hyperplasia; and they develop autoimmune disease In Baff deficient animals, there are defects in peripheral B-cell maturation, and there are decreased levels of circulating immunoglobulins

Serum BAFF Levels

Effect of Clinical Extent and Severity on BAFF Levels

Effect of Presence or Absence of Serum Anti-AChR Antibody on BAFF Levels

Receptors for BAFF Baff-R deficient mice lack marginal zone and follicular B-cells TACI deficient mice have an increased number of peripheral B-cells, they develop autoimmune disease, and they exhibit fatal lymphoproliferation The pro survival signals of Baff are mediated by the Baff-R, whereas the interaction of Baff with TACI delivers inhibitory signals

Immunofluorescent Staining of Peripheral Blood Mononuclear Cells CD3: mouse IgG1-FITC CD20: mouse IgG2a-FITC Baff-R: goat IgG anti human Baff-R + rabbit F(ab)’2 anti goat IgG-Cy5 TACI: biotinylated goat IgG anti human TACI + streptavidin-Cy5

Cell-Surface Expression of BAFF-R and TACI

Thangarajh et al.: MG thymus with hyperplasia: macrophages express Baff Germinal center: B-cells express Baff-R Plasma levels of Baff were not different No differences in the percentages of BCMA, Baff-R, or TACI-positive B-cells Li et al.: Increased percentage of CD19+ Baff-R+ B-cells Kim et al.: Serum Baff levels are higher in MG patients

Myeloid Cells Produce and Secrete BAFF Monocyte Dendritic cell B-cell Baff

Immunofluorescent Staining of Peripheral Blood Monocytes CD14: mouse IgM-FITC Baff: mouse IgG1 anti human Baff + goat F(ab)’2 anti mouse IgG-PE

BAFF Production by Adherent Monocytes

BAFF Production by Adherent Monocytes

BAFF Production by THP-1 Cells THP-1: human acute monocytic leukemia 1 year old male HLA: A2, A9, B5, DRw1, DRw2

BAFF Production by THP-1 Cells

Enrichment of Monocytes by Immunomagnetic Separation PBMC are treated with a mixture of mouse anti CD2, CD7, CD16, CD19, CD56, and CD235a followed by anti mouse IgG-coated magnetic beads

BAFF Production by Monocytes

Dendritic Cell Lineages Banchereau et al., 2000

Differentiation of Monocytes Into Dendritic Cells

Maturation of Dendritic Cells With sCD40L (CD154)

Cytokine Production by Dendritic Cells sCD40L Immature DC Mature DC 254.0 pg/ml IL-4 192.0 pg/ml 5.0 IL-10 5.4 0 IL-12 1.3 0 IL-17 0

BAFF Production by Dendritic Cells

Ueno et al., 2007

Contributors Basic Science Clinical Samia Ragheb, Ph.D. Robert Lisak, M.D. Felicitas Gonzales, B.S. Richard Lewis, M.D. Kirk Simon, B.S. Gregory Van Stavern, M.D. Yanfeng Li, M.S. Wayne State University School of Medicine Supported by the Muscular Dystrophy Association (MDA)