|M.Sc Student||Voloshin-Sela Tali|
|Subject||Recombinant Human Antibodies with TCR-like Specificity|
Directed towards MAGE A (Melanoma Antigen Encoding
Gene) HLA-A2 Restricted Epitopes
|Department||Department of Biology||Supervisor||Professor Yoram Reiter|
|Full Thesis text|
During the past 20 years, significant effort has been devoted towards the
identification of tumor-associated antigens (TAA) recognized by human T
lymphocytes. MAGE (Melanoma antigen encoding gene) genes
are an example of such specific antigens that are expressed in the testis and
in tumors of varying histological origin. In the present work, a major effort
has focused on the generation of recombinant T-cell receptor-like antibodies
that can bind in a peptide-specific manner only to MAGE-A1278-286 and
MAGE-A3112-120 TAA determinants, in association with HLA-A2
molecules. These antibodies were selected from a large nonimmune
human Ab phage library, and an exquisite, very specific, and special binding
pattern. We demonstrated the ability of these Abs to bind
specifically to recombinant class I peptide-MHC complexes, as well
as to complexes presented on the surface of peptide pulsed APCs and to
complexes presented on cancer cells. The isolated Abs can serve later as an
efficient research tool to study antigen presentation, and can also be used for
establishment of clinical applications.
The second part of this work focused on a new subset of CD33 positive T-cells, which were identified recently in our laboratory. These T-cells are induced under polyclonal activation of freshly isolated peripheral blood T-cells, and were found to possess a regulatory role. We analyzed the cytokine profile and biological features of these cells, and found that CD3+CD33+ T-cells secrete high levels of IL4 and low levels of IFNγ and suppress the proliferation of naïve T-cells. Thus, these cells appear to be a novel subset of T-cells with regulatory/inhibitory features. In the present work, in order to support the cytokine secretion data, we examined the expression pattern of the major Th1/Th2/T-reg transcription factors and cytokines of CD3+CD33+ T-cells by quantitative real time PCR analysis. Our results demonstrate that the CD3+CD33+ subpopulation is being induced and maintained under Th2-like expression environment and is distinguished from Th1 cells that drive the inflammatory process towards cellular response.
In order to establish an animal model for the CD33+ T-cells, we attempted to isolate CD33+ subpopulation from murine activated T-cells. We did not observe neither mCD33 mRNA nor mCD33 Protein expression in the different murine T-cells samples regardless to whether they were activated or not. Hence, we conclude that this particular subpopulation does not exist in mice, a statement that is supported with current literature which demonstrates that the mCD33 has a granulocyte restricted expression profile.