Fig. 3

a–k IHC staining for CD117 and CD138 on ST of patients with naïve or MTX-IR PsA and Ab^neg RA patients. Example photos of CD117 (RED) staining of ST biopsies from patients with naïve (a) or MTX-IR (b) PsA and with naïve (c) or MTX-IR (d) Ab^neg RA (magnification × 20 and magnification × 40 in the corresponding inset). Thin black arrows indicate CD117⁺ cells (red) in the corresponding inset. e IHC scores for CD117⁺ cells in PsA and Ab^neg RA patients divided by treatment regimen; *p = 0.0004, naïve PsA vs naïve Ab^neg RA patients; *p = 0.0005, MTX-IR PsA vs MTX-IR Ab^neg RA patients. Example photos of CD138 (DAB) staining of ST biopsies from patients with naïve (f) or MTX-IR (g) PsA and with naïve (h) or MTX-IR (i) Ab^neg RA (magnification × 20 and magnification × 40 in the corresponding inset). Thin black arrows indicate CD138⁺ cells (brown) in the corresponding inset. j IHC scores for CD138⁺ cells in PsA and Ab^neg RA patients divided by treatment regimen; *p = 0.04, naive PsA vs naive Ab^negRA patients; *p = 0.002, MTX-IR PsA vs MTX-IR Ab^neg RA patients. k Rate of distribution of CD117/CD138 IHC combination differentially distributed among PsA and Ab^neg RA patients. IHC immunohistochemistry, PsA psoriatic arthritis, RA rheumatoid arthritis, Ab autoantibody, MTX-IR methotrexate inadequately responder, CD cluster designation