USMLE Forum Archives - USMLE Step 1 - Pathology 33
Pathology 33
TheOne - 11-21-06 16:16
Loss of which of the following classes of molecules on the surface of a tumor cell target would result in loss of susceptibility to killing by host immune cells?
A. CD3
B. CD4
C. CD8
D. MHC class I
E. MHC class II
TheOne - 11-21-06 16:16
Loss of which of the following classes of molecules on the surface of a tumor cell target would result in loss of susceptibility to killing by host immune cells?
A. CD3
B. CD4
C. CD8
D. MHC class I
E. MHC class II
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#2
Re: Pathology 33 Youngdoctor - 11-24-06 17:33 Loss of which of the following classes of molecules on the surface of a tumor cell target would result in loss of susceptibility to killing by host immune cells?
A. CD3
B. CD4
C. CD8
D. MHC class I
E. MHC class II
I guess MHC class II, can any one explain to me.
#3
Re: Pathology 33
TheOne - 11-26-06 13:30 Explanation: The correct answer is D. After the MHC class I molecule has moved to the surface of the tumor cell, peptide fragments from the tumor are presented in a groove of the class I molecule. The peptide fragments are presented to cytotoxic CD8 T cells, which recognize the MHC class I molecules on the cell surface and kill the tumor cell. Loss of this molecule would therefore prevent the tumor cell from being killed. The CD3 molecule (choice A) is a marker on all T cells. It is involved in signal transduction, but not antigen recognition. This molecule would not be on the surface of tumor cells. The CD4 molecule (choice B) is not on the surface of a tumor cell, but it is on the surface of a CD4+ T helper lymphocyte. The CD8 molecule (choice C) is not on the surface of a tumor cell, but it is on the surface of a CD8+ cytotoxic T lymphocyte. MHC class II antigens (choice E) are not involved in killing of tumor cell targets. They present peptide fragments (derived from intracellular killing of extracellular organisms by macrophages) to CD4 T lymphocytes.
#4
Re: Pathology 33 galaxy - 05-28-10 02:25 Loss of which of the following classes of molecules on the surface of a tumor cell target would result in loss of susceptibility to killing by host immune cells?
D. MHC class I
#5
Re: Pathology 33 babbu5508 - 06-21-10 15:31 D. . MHC class I molcules display fragments of proteins from within the cell to T cells; healthy cells will be ignored while cells containing foreign proteins will be attacked by the immune system.
#6
Re: Pathology 33 bingousmle - 06-30-10 22:02 Loss of MHC class I molecules on the surface of a tumor cell target would result in loss of susceptibility to killing by host immune cell..
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