To unravel the potential mediators of Fas proinflammatory and proresorptive signaling, in this study we characterized frequencies of main hematopoietic articular populations in Fas-deficient mice with AIA, analyzed the transcriptome of CD11b+Gr-1+ cells as the most altered subset, and assessed the role of downregulated midline 1 (Mid1) gene as a potential proinflammatory and proresorptive mediator in arthritis. Here, MID1 is linked to arthritic joint disease.