B cell-derived IL-10 is an autocrine survival factor and maintains immune homeostasis in the spleen

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Presentation Time: 11:30 AM - 12:45 PM
Poster Board Number: B819
Abstract ID: 5318

Presenting Author:
Chuxiao Chen , Post-Doctoral Fellow at Univ. of Pittsburgh, UPMC Thomas E. Starzl Transplantation Inst.

Abstract:

IL-10 is a key anti-inflammatory cytokine and IL-10 KO mice develop colitis. Mice with a global IL-10 KO or constitutive B cell-specific IL-10 KO (CD19-Cre.IL-10fl/fl) have otherwise normal B cells. Surprisingly, we found that within 14-21 days, mice with a tamoxifen (Tam) -induced B cell specific deletion of IL-10R (hCD20-ERT2-Cre.IL-10Rfl/fl) had a 50% decrease in splenic B cell number vs. Cre-controls. B cell frequency was unchanged due to a concomitant fall in both T cells and innate cells resulting in a 58% fall in splenocyte number. Plasma cells, CD4+ and CD8+ T cells, and neutrophils were disproportionately decreased, resulting in a 20-40% reduction in frequency. A similar but somewhat less severe loss of B cells/splenocytes was seen in Tam-treated hCD20-ERT2-Cre.IL-10fl/fl mice. Adoptive transfer competition studies in immunized µMT hosts treated with Tam revealed a selective loss of hCD20-ERT2-Cre.IL-10fl/fl vs. CD19-Cre.IL-10fl/fl B cells. Furthermore, by day 21, acute loss of B cell IL-10 or IL-10R resulted in ~20% weight loss and colon length, consistent with colitis (pathology pending). In conclusion, IL-10 is an autocrine B cell survival factor and acute loss of B cell IL-10 or IL-10R is associated with a marked contraction of B cells and associated collapse in T cells and innate cells in the spleen, resulting in immune dysregulation and colitis. This requirement for B cell IL-10 has not been previously recognized because it is compensated for developmentally.