TUMOR ESCAPE MECHANISMS

Question 1

what are the tumor escape mechanisms?

Answer 1

selective outgrowths of antigen negative variants

loss or reduced expression of HLA antigens

lack of co-stimulation

immunosuppression

apoptosis of cytotoxic T-cells

Question 2

during tumor progression strongly immunogenic sub clones may be eliminated

Answer 2

selective outgrowth of antigen negative variants

Question 3

tumor cells may fail to express normal levels of HLA class I molecules, thereby escaping attack by cytotoxic T-cells

Answer 3

loss or reduced expression of HLA antigens

Question 4

sensitization of T cell requires 2 signals:

1 by a foreign peptide presented by MHC molecules and the other by costimulatory molecules; although tumor cells may express peptide antigens with class I molecules, they often do not express costimulatory molecules

prevents sensitization and renders T cells anergic

Answer 4

lack of co-stimulation

Question 5

many oncogenic agents like chemicals and ionizing radiation suppress host immune responses; tumors or tumor products are also immunosuppressive

Answer 5

immunosuppression

Question 6

eliminates tumor specific T cells

Answer 6

apoptosis of cytotoxic T-cells