[HTML][HTML] Activation-induced cytidine deaminase deficiency causes organ-specific autoimmune disease

K Hase, D Takahashi, M Ebisawa, S Kawano, K Itoh… - PloS one, 2008 - journals.plos.org
K Hase, D Takahashi, M Ebisawa, S Kawano, K Itoh, H Ohno
PloS one, 2008journals.plos.org
Activation-induced cytidine deaminase (AID) expressed by germinal center B cells is a
central regulator of somatic hypermutation (SHM) and class switch recombination (CSR).
Humans with AID mutations develop not only the autosomal recessive form of hyper-IgM
syndrome (HIGM2) associated with B cell hyperplasia, but also autoimmune disorders by
unknown mechanisms. We report here that AID−/− mice spontaneously develop tertiary
lymphoid organs (TLOs) in non-lymphoid tissues including the stomach at around 6 months …
Activation-induced cytidine deaminase (AID) expressed by germinal center B cells is a central regulator of somatic hypermutation (SHM) and class switch recombination (CSR). Humans with AID mutations develop not only the autosomal recessive form of hyper-IgM syndrome (HIGM2) associated with B cell hyperplasia, but also autoimmune disorders by unknown mechanisms. We report here that AID−/− mice spontaneously develop tertiary lymphoid organs (TLOs) in non-lymphoid tissues including the stomach at around 6 months of age. At a later stage, AID−/− mice develop a severe gastritis characterized by loss of gastric glands and epithelial hyperplasia. The disease development was not attenuated even under germ-free (GF) conditions. Gastric autoantigen -specific serum IgM was elevated in AID−/− mice, and the serum levels correlated with the gastritis pathological score. Adoptive transfer experiments suggest that autoimmune CD4+ T cells mediate gastritis development as terminal effector cells. These results suggest that abnormal B-cell expansion due to AID deficiency can drive B-cell autoimmunity, and in turn promote TLO formation, which ultimately leads to the propagation of organ-specific autoimmune effector CD4+ T cells. Thus, AID plays an important role in the containment of autoimmune diseases by negative regulation of autoreactive B cells.
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