Project Grant R01AI185514

ROLE OF TIM-L IN B CELLS IN REGULATING AUTOIMMUNITY IN THE CNS - PROJECT SUMMARY ACCUMULATING EVIDENCE SUPPORTS THAT B CELL CAN REGULATE IMMUNE RESPONSES AND ARE ESSENTIAL FOR LIMITING INFLAMMATION AND AUTOIMMUNITY BY IL-10-DEPENDENT AND -INDEPENDENT MECHANISMS. THE PROCESSES AND MECHANISMS BY WHICH B CELLS WITH REGULATORY PROPERTIES ARE GENERATED HAVE ALSO NOT BEEN IDENTIFIED. WE HAVE SHOWN THAT TIM-1 IS ALSO EXPRESSED ON B CELLS THAT PRODUCE IL-10 AND TIM-1 IS REQUIRED FOR APOPTOTIC CELL (AC) BINDING TO B CELLS AND INDUCTION OF IL-10. WE GENERATED A MOUSE WITH A CONDITIONAL DELETION OF TIM-1 SELECTIVELY ON B CELLS (TIM-1BKO). THE TIM-1BKO MICE SHOW PROGRESSIVE LOSS OF IL-10 PRODUCTION IN B CELLS AND, WITH AGE, DEVELOPED SEVERE MULTI-ORGAN TISSUE INFLAMMATION INCLUDING COLITIS, DERMATITIS, HEPATITIS AND A PARALYTIC DISEASE WITH MENINGEAL INFLAMMATION IN THE CNS. ON THE OTHER HAND, TIM-1BKO MICE SHOW STRONG ANTI-TUMOR IMMUNITY WITH INHIBITION OF TUMOR GROWTH. THEREFORE, IN ADDITION TO SERVING AS A MARKER FOR REGULATORY FUNCTION OF B CELLS, TIM-1 AS A PHOSPHATIDYLSERINE RECEPTOR IS ALSO FUNCTIONALLY REQUIRED FOR OPTIMAL REGULATORY B CELL FUNCTION. HOWEVER, IT IS NOT CLEAR WHAT INDUCES TIM-1 EXPRESSION AND WHAT ARE THE TRANSCRIPTION FACTORS THAT DRIVE TIM-1 EXPRESSION AND REGULATORY B CELL FUNCTION. OUR DATA CLEARLY SHOWS THAT TIM-1 DOES NOT DEFINE A SUBSET OF B CELLS BUT CAN BE INDUCED ON B CELL UPON ACTIVATION. BASED ON THE PRELIMINARY DATA WE HYPOTHESIZE THAT TIM-1 IS A FUNCTIONAL MARKER ON B CELLS THAT CAN INDUCE IL-10 UPON BINDING TO AC AND REGULATE TISSUE INFLAMMATION, AUTOIMMUNITY, AND ANTI-TUMOR IMMUNITY. TO ADDRESS THIS HYPOTHESIS WE PROPOSE TO: 1) IDENTIFY TRANSCRIPTIONAL REGULATORS OF TIM-1+ B CELLS, FOCUSING ON EHF AS THE POSITIVE REGULATOR OF TIM-1, WHICH WAS IDENTIFIED BY A FOCUSED CRISPR-CAS9 SCREEN; 2) STUDY THE EFFECT OF LOSS OF TIM-1 ON B CELLS IN GENERATING PRO-INFLAMMATORY EFFECTOR B CELLS, AS TIM-1BKO B CELLS ARE HIGHLY ACTIVATED AND PRODUCE PROINFLAMMATORY CYTOKINES INCLUDING IL-23 AND IL-6 WHICH PROMOTE DIFFERENTIATION OF PATHOGENIC TH17 CELLS; 3) STUDY THE ROLE OF TIM-1+ B CELLS IN MAINTAINING STEM-LIKE TH17 CELLS AND LIMIT DIFFERENTIATION OF PATHOGENIC CXCR6+ TH17 CELLS. WE HAVE FOUND THAT TIM-1+ B CELLS PRODUCE WNT10A, WHICH PROMOTES STEMNESS, AND OTHER SUPPRESSIVE CYTOKINES THAT KEEP TH17 CELLS IN A STEM-LIKE STATE AND LIMIT THEIR DIFFERENTIATION INTO PATHOGENIC TH17 CELLS. THE PROPOSED STUDIES WILL GREATLY INCREASE OUR UNDERSTANDING OF THE ROLE OF TIM-1 IN B CELLS AND THE GENERATION OF REGULATORY ACTIVITY ON B CELLS TO PROMOTE IMMUNE TOLERANCE AND LIMIT TISSUE INFLAMMATION AND AUTOIMMUNITY. THESE STUDIES WILL PROVIDE A NOVEL THERAPEUTIC STRATEGY BY TARGETING B CELLS FOR THE TREATMENT OF AUTOIMMUNE DISEASES AND PROMOTING ANTI-TUMOR IMMUNITY.