CD74

CD74, also known as the MHC Class II-associated invariant chain (II), is a Type II transmembrane protein which binds to the peptide-binding groove of newly-synthesized MHC class II alpha/beta heterodimers and prevents their premature association with endogenous polypeptides. CD74 is expressed primarily by antigen-presenting cells such as B-lymphocytes (from before the pre-B-cell stage to before the plasma-cell stage), macrophages and monocytes, together with many epithelial cells.

CD74 stains predominantly germinal-center lymphocytes and B-cell lymphomas but rarely T-cell lymphomas. It stains the cell membrane but a paranuclear globular labeling is also noted. CD74 is useful in differentiating Atypical Fibroxanthoma from Malignant Fibrous Histiocytoma, as well as Small-cell Lung Carcinoma from Non-small cell Lung Carcinomas.

CD74 antibody is a mouse monoclonal from ascites fluid diluted in Phosphate Buffered Saline, pH 7.6, with protein base, and preserved with Sodium Azide preservative.

1. Chan JKC, et al. Histopathology. 1994;25:517-536.
2. Kasaian MT, et al. Proc of the Soc for Exp Bio and Med. 1991;197:226-241
3. Jones NH, et al. Nature. 1986;323:346-349

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.