Question

Major histocompatibility antigens are

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

Answer 1

Major histocompatibility antigens are glycoproteins on cell membranes that present antigens to T cells, vital for immune response. There are two types, MHC class I found on all nucleated cells and MHC class II on professional antigen-presenting cells like macrophages, dendritic cells, and B cells.

Step-by-step explanation:

The major histocompatibility antigens are glycoproteins found in the cytoplasmic membranes of most vertebrate animal cells, which makes option C the correct answer. These MHC molecules play a vital role in the immune system by presenting processed antigens on the cell surface, which are then recognized by T cells. There are two types of MHC molecules: MHC class I and MHC class II.

MHC class I molecules present antigens derived from intracellular pathogens, like viruses, and are found on all nucleated cells, enabling them to elicit a cytotoxic T cell response. In contrast, MHC class II molecules are expressed only on professional antigen-presenting cells, such as macrophages, dendritic cells, and B cells, and they present antigens that come from extracellular sources like bacteria and fungi.

The combination of an MHC molecule and a peptide fragment is what T cells recognize, marking the start of an adaptive immune response.