Alteration of function and specificity of TFH in SLE

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Project Summary/ Abstract Systemic lupus erythematosus (SLE) is a chronic and complex autoimmune disease and pathogenic mechanisms are not well understood. Based on data from SLE patients and GWAS, we developed a mouse model to phenocopy the expression pattern of the PRDM1 risk allele. Mice with a selective deficiency of BLIMP1 in dendritic cells (DCs) (Prdm1 CKO mice) develop SLE with an increased number of T follicular helper cells (TFH) and autoantibodies arising in a germinal center response. Only female mice develop disease. The central hypothesis for the proposed studies is that BLIMP1-deficient DCs alter the selection of T cells in the thymus. We further hypothesize that estrogen and estrogen-receptor mediated signaling play a critical role in BLIMP1-deficient DC function, altering antigen presentation and synergizing with BLIMP1 deficiency to skew to TFH differentiation. The following aims will address these hypotheses. Aim 1 will determine if the altered TFH repertoire in female Prdm1 CKO mice is determined during thymic selection. We will identify whether BLIMP1-deficient DCs alter the strength of TCR signaling to alter the T cell repertoire. We will explore the function of TFH in female Prdm1 CKO mice and female control mice, and their activation of autoreactive B cells. Aim 2 will investigate functional changes in DCs and TFH conferred by estrogen receptor signaling. These studies should suggest therapeutic strategies in a defined subset of SLE patients, and advance precision medicine in a disease where many agree that the failure of clinical trials reflects an inadequate understanding of patient heterogeneity.