The rat macrophage scavenger receptor CD163: Expression, regulation and role in inflammatory mediator production

The monoclonal antibody ED2 is widely used to define macrophages (mϕ)(mϕ) in the rat. We have recently identified the ED2 antigen as the rat CD163 glycoprotein. CD163 is a member of the scavenger receptor cysteine-rich group B (SRCR-B) family and functions as a scavenger receptor for hemoglobin–haptoglobin complexes. Moreover, CD163 has also been indicated as a marker for alternatively activated mϕmϕ. In the current study, we identify rat CD163/ED2-antigen as a marker for mature tissue mϕmϕ. Rat CD163 is constitutively expressed on most subpopulations of mature tissue mϕmϕ, including splenic red pulp mϕmϕ, thymic cortical mϕmϕ, Kupffer cells in the liver, resident bone marrow mϕmϕ and central nervous system perivascular and meningeal mϕmϕ, but is apparently absent from monocytes. Rat CD163 expression can be promoted by glucocorticoids, and this can be further enhanced by IL4. Finally, engagement of rat CD163 on peritoneal mϕmϕ induces the production of pro-inflammatory mediators, including NO, IL-1β1β, IL-6 and TNF-αα. Collectively, our findings identify rat CD163 as a broadly expressed macrophage scavenger receptor that may play a role in the activation of mϕmϕ during hemolytic and/or inflammatory conditions.