CD8 is a cell surface receptor expressed either as a heterodimer with the beta chain or as a homodimer. A majority of thymocytes and a subpopulation of mature Tcells and NK cells express CD8a. It binds to MHC class 1 and through its association with protein tyrosine kinase p56lck plays a role in Tcell development and activation of mature Tcells. For mature Tcells, CD8 and 4 are mutually exclusive, so antibody to CD8 is generally used in conjunction with antibody to CD4. CD8a antibody is a useful marker for distinguishing helper/inducer T-lymphocytes, and most peripheral Tcell lymphomas are CD4+/CD8-. Anaplastic large cell lymphoma is usually CD4+/CD8-, and in T-lymphoblastic lymphoma/leukemia, they are often co-expressed. It is also found in littoral cell angioma of the spleen.

Store the CD8a antibody at 2-8°C (with azide) or aliquot and store at -20°C or colder (without azide).