IMMUNOLOGY

Detailed explanation-1: -T cells can detect the presence of an intracellular pathogen because infected cells display on their surface peptide fragments derived from the pathogen’s proteins. These foreign peptides are delivered to the cell surface by specialized host-cell glycoproteins.

Detailed explanation-2: -Antigens are markers that tell your body that something is foreign. Your immune cells make antibodies to recognize and destroy harmful antigens. In fact, you can think of antigens as antibody generators. Antibodies are very specific to the antigens they recognize and destroy.

Detailed explanation-3: -Immune markers are proteins that determine our ability to resist harmful agents such as bacteria and other foreign substances.

Detailed explanation-4: -Antigens, small molecules, or peptides capable of eliciting an immune response are key elements in this process of distinguishing self from nonself. Antigens serve as labels that enable the immune system to distinguish between a normal interaction (self) and an encounter with a foreign threat (nonself).

Detailed explanation-5: -Any substance that causes the body to make an immune response against that substance. Antigens include toxins, chemicals, bacteria, viruses, or other substances that come from outside the body.

Detailed explanation-6: -T Cells Recognize Foreign Peptides Bound to MHC Proteins As discussed earlier, both cytotoxic T cells and helper T cells are initially activated in peripheral lymphoid organs by recognizing foreign antigen on the surface of an antigen-presenting cell, usually a dendritic cell.