Question

MHCs are present as self antigens on all body cells except
A. RBCs
B. WBCs
C. Lymphocytes
D. Tissue cells

Answer 1

Hint: MHCs are generally not found on the surface of enucleated cells. Except these, all body cells having a nucleus usually have MHCs to project or display an antigen on the cell surface prior after the binding. Here, the cells without MHCs usually contain hemoglobin that ultimately plays a role in transport of oxygen.

Complete answer:
MHC is an abbreviated form of major histocompatibility complex. It is basically a group of genes that usually encode for proteins (or MHC molecules) found on the surface of those cells which have a nucleus. A cell devoid of a nucleus does not have MHC molecules on their surfaces. MHC molecules bind the peptide fragments that are derived from pathogenic organisms. These are then displayed or projected on the cell surface as antigens for their recognition by certain specialized immune cells (T cells).
RBCs are the red blood cells that generally do not have a nucleus. Unlike RBCs, all other cells mentioned in the rest of the options including WBCs (white blood cells), lymphocytes, and tissue cells are carrying a nucleus. Thus, these nucleated cells are likely to have MHCs present as self antigens on all body cells. However, RBCs being enucleated do not have MHC molecules on their cell surface.

The correct answer is option A, representing RBCs.

Note:
WBCs are also referred to as leukocytes, and play a crucial role in the immune system by acting as soldier cells of the body due to their ability to fight against pathogens aiming to attack the body cells or tissues. Lymphocytes are the plasma cells, and are classified into two categories including B lymphocytes and T lymphocytes. The cells contributing to structure of a tissue are commonly referred to as tissue cells.