The CD19-CD21 signal transduction complex of B lymphocytes regulates the balance between health and autoimmune disease: systemic sclerosis as a model system.
Cell-surface CD19 functions as a general rheostat for defining intrinsic and antigen receptor-induced signaling thresholds critical for clonal expansion of the B cell pool and humoral immunity. CD19 also governs B cell responses initiated through the CD21 receptor, where complement C3d binding to CD21 links humoral immune responses with the innate immune system. Alterations in this signaling pathway can predispose mice and humans to autoantibody production and systemic autoimmunity. Transgenic mice that overexpress CD19 by 20-170% lose tolerance and generate autoantibodies. Likewise, B cells from CD21-deficient mice overexpress CD19 by approximately 50%, which leads to autoantibody production. Autoimmune patients with systemic sclerosis also overexpress CD19 by approximately 20%, which may contribute to their intrinsic B cell abnormalities and autoantibody production. Thus, chronic B cell activation resulting from augmented CD19 expression or signaling through the CD19 pathway may reveal a prototype autoimmune disease susceptibility pathway in mice and humans.
Tedder
Thomas F
TF
Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA. thomas.tedder@duke.edu
Poe
Jonathan C
JC
Fujimoto
Manabu
M
Haas
Karen M
KM
Sato
Shinichi
S
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D018941:Antigens, CD19 / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D001327:Autoimmune Diseases / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D020013:Calcium Signaling; D015815:Cell Adhesion Molecules / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018448:Models, Immunological; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D017464:Receptors, Complement 3d / Q000172:deficiency / Q000378:metabolism*; D012595:Scleroderma, Systemic / Q000201:enzymology / Q000276:immunology*; D051918:Sialic Acid Binding Ig-like Lectin 2; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism
D015703:Antigens, CD; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D011947:Receptors, Antigen, B-Cell; D017464:Receptors, Complement 3d; D051918:Sialic Acid Binding Ig-like Lectin 2; D019061:src-Family Kinases