Pérez RM

Language: Spanish
References: 7
Page: 7-10
PDF size: 312.81 Kb.

ABSTRACT

The major histocompatibility complex molecules (MHC) bind self or foreign antigens and present them to T lymphocytes. Newly synthesized alpha chain of MHC class I is associated with calnexin protein in the endoplasmic reticulum (ER). The alpha chain then binds with β₂-microglobulin and calnexin is substituted by calreticulin. This complex has association with other chaperone proteins, ERp57 and tapasin. MHC class I molecules are loaded with peptides of length 8-11 aminoacids derived from intracellular proteins, which were hydrolyzed by proteasomes. These peptides are translocated into the lumen of the ER by TAP (transporter associated with antigen processing), where they can proceed to bind MHC class I groove. The newly synthesized MHC class II heterodimer is escorted by the invariant protein (Ii) from the ER into the MCII and prevents premature association of any antigenic peptide by insertion of CLIP (class II-associated invariant chain peptide) within the peptide-binding site. After Ii is degraded by proteolytic enzymes, CLIP is removed by HLA-DM molecule and a peptide of 25 aminoacids is loading into the MHC class II groove. Finally the MHC class II molecules, on the surface of antigen presenting cells, present antigenic peptides to CD4+ T cells.

REFERENCES

1. Griffin TA, Nandi D, Cruz M, Fehling H, Van-Kaer L, Monaco JJ, et al. Immunoproteasome assembly: cooperative incorporation of interferon γ (IFN-γ)-inducible subunits. J Exp Med 1998; 187(1):97-104.

2. Sadasivan B, Lehner PJ, Ortmann B, Spies T, Cresswell P. Roles for calreticulin and a novel glycoprotein, tapasin, in the interaction of MHC class I molecules with TAP. Immunity 1996; 5(2):103-114.

3. Williams A, Peh CA, Elliott T. The cell biology of MHC class I antigen presentation. Tissue Antigens 2002; 59(1): 3-17.

4. Harris MR, Lybarger L, Yu YYL, Myers NB, Hansen TH. Association of ERp57 with mouse MHC class I molecules is tapasin dependent and mimics that of calreticulin and not calnexin. J Immunol 2001; 166(11):6686-6692.

5. Pieters J. MHC class II restricted antigen presentation. Curr Opin Immunol 1997; 9(1):89-96.

6. Weenink S, Gautam AM. Antigen presentation by MHC class II molecules. Immunol Cell Biol 1997;75(1):69-81.

7. Villadangos JA, Schnorrer P, Wilson NS. Control of MHC class II antigen presentation in dendritic cells: a balance between creative and destructive forces. Immunol Rev 2005; 207:191-205.