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

The monoclonal antibody ED2 is widely used to define macrophages ( m ϕ ) 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 m ϕ . In the current study, we identify rat CD163/ED2-antigen as a marker for mature tissue m ϕ . Rat CD163 is constitutively expressed on most subpopulations of mature tissue m ϕ , including splenic red pulp m ϕ , thymic cortical m ϕ , Kupffer cells in the liver, resident bone marrow m ϕ and central nervous system perivascular and meningeal m ϕ , 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 m ϕ induces the production of pro-inflammatory mediators, including NO, IL- 1 β , IL-6 and TNF- α . Collectively, our findings identify rat CD163 as a broadly expressed macrophage scavenger receptor that may play a role in the activation of m ϕ during hemolytic and/or inflammatory conditions.