Major Histocompatibility Antigens Are

Major histocompatibility antigens are

A) glycoproteins found in the cytoplasmic membranes of most vertebrate animal cells.
B) antigens attached to foreign invaders.
C) antigens that provoke allergic reactions.
D) not really antigens, but rather antibodies produced to mask foreign antigens.
E) antigens that must be processed by cells called histiocytes in order to be recognized by the immune system.