CD99

CD99, also known as MIC-2 or single-chain Type-1 glycoprotein, is a human protein encoded by the CD99 gene. The protein has a MW of 32 kD. It is expressed on all leukocytes but highest on thymocytes, and is believed to augment T-cell adhesion and apoptosis of double-positive T-cells. It also participates in migration and activation.

The CD99 antigen is found on the cell membrane of Ewing’s Sarcoma and Primitive Peripheral Neuroectodermal Tumors (PNET). It is also present on a variety of other cell types including bone marrow, lymph nodes, spleen, cortical thymocytes, granulosa cells of the ovary, beta cells, CNS ependymal cells, Sertoli’s cells of the testis and a few endothelial cells. Mature granulocytes, however, tend to express very little or no CD99. MIC-2 has also been identified in Lymphoblastic Lymphoma, Rhabdomyosarcoma, Mesenchymal Chondrosarcoma, and Thymoma.

CD99 is 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. Rettig WJ, et al., Lab Invest. 1992;66:133
2. Fellinger EJ, et al., Amer J Surg Pathol. 1992;16(8):746
3. Ambros IM, et al., Cancer. 1991;139:317
4. Goodfellow PN, Tippett P, Nature. 1981;289:404

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.