Unit 4 AOS 1

Pathogen

Pathogen

An agent that causes disease in a host.

Antigen

Any molecule that may trigger an immune response.

MHC

A group of receptor proteins present on the surface of body cells that help distinguish the body’s proteins from foreign proteins.

MHC-I

Receptor proteins found on all nucleated body cells, marking cells as self to prevent immune system attacks.

MHC-II

Receptor proteins found on antigen-presenting cells, interacting with T helper cells during antigen presentation.

Prions

Normal proteins in the nervous system that change shape and become infectious, affecting other proteins they contact.

Viruses

Infectious agents composed of genetic material inside a protein coat, causing disease by replicating in host cells.

Bacteria

Unicellular prokaryotes that can cause disease through toxins and enzymes, reproducing through binary fission.

Defensins

Small peptides toxic to microbes and fungi, part of the plant's chemical defense.

NK Cells

Cells that destroy infected or abnormal cells with insufficient MHC Class I markers.

Phagocytes

Cells that consume and destroy foreign or dead material in the body through phagocytosis.

Complement Proteins

Proteins that react with each other in the presence of pathogens, leading to opsonization, chemotaxis, and lysis.

Antigen Presentation

Process where an APC engulfs and presents antigens to T cells, initiating the adaptive immune response.

Lymphocytes

Cells involved in the immune response, including memory B cells, plasma B cells, T helper cells, and cytotoxic T cells.

Antibodies

Proteins composed of polypeptide chains that bind to antigens, immobilizing pathogens and activating complement proteins.