PTIP Deficiency in B Lymphocytes Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Mice

Immune dysregulation contributes to the development of ulcerative colitis (UC). The research on the inflammatory response of UC is mainly focused on T cells, with less understanding of the role of B cells. Pax transactivation domain-interacting protein (PTIP) is essential for the development of B cell subpopulations and humoral immunity. The purpose of this study was to elucidate the role of PTIP in B cells of mice with dextran sodium sulfate (DSS)-induced colitis.

The B-cell-specific PTIP knockout (PTIP^-/-) mice were established by crossbreeding cluster of differentiation (CD)19^cre/cre mice with PTIP^flox/flox mice. The UC mice were induced by drinking water supplemented with 3.8% Dextran Sulfate Sodium (DSS) (PTIP^-/- + DSS). The histological analysis was performed using hematoxylin and eosin staining. The immune cells were isolated using a fluorescence-activated cell sorter. The serum antibodies (immunoglobulin M (IgM) or immunoglobulin G (IgG)) and tumor necrosis factor (TNF)-α were determined by Enzyme linked immunosorbent assay (ELISA).

Interestingly, our findings demonstrate that PTIP deficiency in B cells significantly ameliorates UC. In contrast to PTIP^-/- + DSS, the wild type (WT) + DSS group showed a more robust increase in disease activity index (DAI) scores (p < 0.05), a substantially shortened colon (p < 0.001) and a decrease of mucous-producing goblet cells and the complete destruction of crypts. Moreover, PTIP-deficient mice manifested markedly altered neutrophil and T-cell distribution in UC (p < 0.05). Although anti-commensal IgG exacerbates UC, we demonstrated, for the first time, that serum natural IgG does not aggravate the pathology of UC. Furthermore, PTIP regulates UC by controlling B-2 cells independently from T cells.

Transplantation of splenic B-2 cells from PTIP-deficient mice protected recipient NOD/ShiltJGpt-Prkdcem26Cd52Il2rgem26Cd22/Gpt (NCG) mice from severe UC.