CONCISE REPORT Colon mucosa of patients both with spondyloarthritis and Crohn’s disease is enriched with macrophages expressing the scavenger receptor CD163

Background: Crohn’s disease is associated with an increased number of macrophages in ileal and colonic mucosa. Data on macrophages in gut mucosa of patients with spondyloarthritis (SpA) are scarce. Objective: To investigate macrophages and other antigen presenting cells in gut mucosa from patients with SpA and Crohn’s disease, given the relationship between both entities. Methods: Biopsy specimens from patients with SpA, Crohn’s disease, ulcerative colitis, and from controls were immunohistochemically stained with different markers for macrophages and dendrit ic cells. Slides were scored semiquantitatively on a four point scale. Results: SpA and Crohn’s disease were associated with large numbers of CD68 macrophages. Colon mucosa of both patients with SpA and Crohn’s disease, but not ulcerative colitis, showed increased numbers of macrophages expressing the scavenger receptor CD163. Conclusions: Macrophages expressing the scavenger receptor CD163 are increased in colonic mucosa in SpA and in Crohn’s disease, highlighting the relationship between these entities. The increased number of CD163 macrophages in colon mucosa of patients with SpA suggests this is another argument for a role of macrophage scavenger receptors in this group of diseases.