CD163

CD163 is a 130 kDa membrane glycoprotein. CD163 was recently identified as an acute phase-regulated transmembrane protein whose function is to mediate the endocytosis of haptoglobin-hemoglobin complexes. Solubilized in plasma, CD163 functions as an anti-inflammatory signal and has many roles in disease processes that range from autoimmune conditions such as Rheumatoid Arthritis to Atherosclerosis. CD163 is expressed exclusively on the cell surface of human monocytes and macrophages that evolve predominantly in the late phase of inflammation, and is, therefore, very useful for macrophage-phenotyping. This receptor is expressed on the surface of monocytes (low expression) and histiocytes (high expression).

Staining for CD163 has been helpful in distinguishing synovial macrophages from synovial intimal fibroblasts in the setting of Rheumatoid Arthritis, where its specificity for macrophages was found to be superior to that of CD68, which does not discriminate between these cell types. Flow-cytometry studies have confirmed that CD163 expression is limited to Leukemias with monocytic differentiation. Positive staining can be seen in the skin (histiocytes), gut, Kupffer cells, a few aveolar macrophages, the main population of macrophages in the placenta, and in varying degrees in macrophages in inflammed tissue including tumor tissue, depending on the inflammatory stage. Redpulp, not white-pulp, macrophages in the spleen and cortical macrophages of the thymus are stained by CD163.

CD163 is a mouse monoclonal antibody derived from cell culture supernatant that is concentrated, dialyzed, filter sterilized and diluted in buffer pH 7.5, containing BSA and sodium azide as a preservative.

1. Van den Heuvel MM, et al. J Leukoc. Biol. 1999;66(5):858–66
2. Matsushita N, et al. Clin. Exp. Immuno. 2002;130(1):156–61
3. Buechler C, et al. J Leukoc Biol. 2000;67:97-103
4. Kristiansen M, et al. Nature. 2001;409:198-201

1. Cut and mount 3-4 micron formalin-fixed paraffin-embedded tissues on positive charged slides.
2. Air dry for 2 hours at 58° C.
3. Deparaffinize, dehydrate and rehydrate tissues.
4. Subject tissues to heat epitope retrieval using a suitable retrieval solution such as ImmunoDNA Retriever with Citrate (BSB 0020-BSB 0023) or EDTA (BSB 0030-BSB 0033).
5. Any of three heating methods may be used:
   • Electric Pressure Cooker
     Place standoff rack at base of pressure cooker. Add 1-2 inches of distilled water to the pressure cooker and turn heat to high, and incubate for 15 minutes. Open and immediately transfer slides to room temperature.
   • Water Bath Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a water bath set at 95°-99° C. Incubate for 30-60 minutes.
   • Conventional Steamer Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a Steamer, cover and steam for 30-60 minutes.
6. After heat treatment, transfer slides in ImmunoDNA Retriever with Citrate or EDTA to room temperature and let stand for 15-20 minutes.
7. Wash slides with IHC wash buffer or DI water.
8. Continue IHC staining protocol.