Overlapping macrophage immune profiles in polymyalgia rheumatica and giant cell arteritis

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are closely related chronic inflammatory diseases in which macrophages play a central role in the pathogenesis. This study compared macrophage-related immune profiles in subacromial bursal tissues affected by PMR and temporal arteries affected by GCA to identify shared therapeutic targets.

Subacromial bursa biopsies (SABBs) were obtained from patients with active PMR (n = 11). Temporal artery biopsies (TABs) were collected from 14 patients with GCA. Immunohistochemical staining was performed for macrophage markers [CD68, CD64, CD86, CD206 and folate receptor (FR) β] and macrophage-related cytokines (GM-CSF, IL-6, IL-23, IFN-γ, M-CSF and TNF-α). The percentage of positively stained cells was quantitatively scored.

All macrophage-related markers and cytokines were expressed in both PMR-affected SABBs and GCA-affected TABs. The proportions of cells expressing macrophage markers (CD68, CD64, CD86 and CD206) and macrophage-related cytokines (GM-CSF, IL-6, IL-23, IFN-γ, M-CSF and TNF-α) were comparable between the two tissue types. However, the expression of FRβ was relatively higher in GCA TABs than in PMR SABBs.

The macrophage immune profiles are remarkably similar in PMR SABBs and GCA TABs. This study underscores the concept of PMR and GCA as a disease spectrum and identifies shared therapeutic targets for both PMR and GCA.