טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentSinik Keren
SubjectStudy of Antigen Processing and Presentation by Constitutive
and Immuno-Proteasomes
DepartmentDepartment of Biology
Supervisors Professor Michael Glickman
Professor Yoram Reiter
Full Thesis textFull thesis text - English Version


Abstract

Class I pMHC complexes are used by the immune system to differentiate between self and non-self. It is well established that the class I MHC expression is altered by cytokines, specifically by IFNg. However, the influence of IFN on antigen presentation and processing is not yet elucidated.

We study the influence of IFNg on the presentation of differentiation antigens-derived HLA-A2-peptide complexes on the surface of melanoma cells using unique antibodies that bind specific HLA-A2-peptide complexes with T-cell receptor-like specificity and with high affinity. Using TCR-like antibodies specific to melanoma-derived HLA-A2/p complexes, we study the influence of IFNg on the presentation of specific melanoma antigens such as gp100, Mart1/MelanA and Tyrosinase. Wester blot analysis enables us to examine intracellular expression levels of the proteins from which these epitopes are derived and to follow the changes in expression of proteasome subunits of constitutive versus immunoproteasomes.

We demonstrate that there is no direct correlation between the increase in the presentation of specific epitopes compared to the general increase in total HLA expression. Moreover, we show that IFNγ has a selective effect on antigen presentation. While the presentation of one epitope is not affected, two epitopes show significant higher levels of presentation after stimulation by IFNγ. This effect does not correlate with protein expression levels or with their degradation rate. The effects of IFNγ were accompanied by replacement of constitutive proteasomes subunits to immunoproteasome. shRNA assays enable us to determine the mechanism by which this selective effect of INFγ is controlled.