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CD Markers


Reviewers: Nat Pernick, M.D. (see Reviewers page)
Revised: 20 January 2011, last major update January 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Receptor important in CD4+ T cell activation


● T cells require 2 signals for full activation: (1) binding of the antigen/MHC complex on the antigen presenting cell to the T cell receptor; (2) interaction of CD28 with its ligands CD80 (B7-1) or CD86 (B7-2), found on activated B cells and called a costimulation signal
● The costimulatory signal induces T cell activation and survival, interleukin-2 production, T-helper type 2 development and clonal expansion
● CD28 is a constitutive, high abundance, low affinity receptor; its binding also increases expression of CTLA4 (CD152), a structurally related cell surface receptor on T cells which competes with CD28 for the same ligands, but has opposite effects (J Clin Immunol 2002;22:1, Curr Pharm Des 2006;12:149)
● CD8+, CD28+ T cells are antigen specific cytotoxic T cells (class I restricted), and constitute 90% of CD8+ T cells
● CD8+, CD28- T cells are suppressor T cells; increased in various infectious diseases and autoimmune diseases and associated with aging



Competition between CTLA4 and CD28 for same ligands


CD28 costimulation is also required for proper memory cell activation

Clinical features

● An imbalance in CTLA-4/CD28 expression at the maternal-fetal interface may confer susceptibility to unexplained pregnancy loss (Int J Gynaecol Obstet 2006;93:123)
● Loss of T cell CD28 expression is associated with aging, and the frequency of CD28(null) T cells predicts immune incompetence in elderly; these T cells are functionally active and long-lived, but have no/limited proliferative capacity (Trends Immunol 2009;30:306)


● No significant clinical use by pathologists

Positive staining - normal

● CD4+ T cells (95%), CD8+ T cells (50%); activated B cells, thymocytes, plasma cells (some)

Positive staining - disease

● Myeloma (95%)

Additional references

MIM 186760, Blood 2005;105:13

End of CD Markers > CD28

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