Immune System | 21.2: Second Line of defense (Interferons and Complement System and some cells) | Part 2

Whats the bodies second line of defense?

Nonspecific internal defenses

• Antimicrobial substances (chemical)

• Cells

• Physiological responses

What are examples of Nonspecific internal defenses: Antimicrobial substances (chemicals)?

• Interferons

• Complement System

• Iron-binding proteins (Transferrin, Ferritin, Hemoglobin)

• Antimicrobial proteins

What are examples of Nonspecific internal defenses: Physiological responses?

• Inflammation

• Fever

What are examples of Nonspecific internal defenses: Cells

• Phagocytes

  • Macrophages

  • Neutrophils

  • Monocytes

  • Dendritic Cells

  • Eosinophills

• Natural Killer Cells

What are the two types of macrophages?

• Wandering

• Fixed

What chemical is produced by virus-infected cells (sometimes bacterial) and various types of immune cells

Interferons

Can the immune system save the cell that is virus infected?

No

• But that cell can save the surrounding cells

What do interferons do to protect body cells and tissues from viruses (sometimes bacteria)?

• They signal neighboring uninfected cells to destroy RNA and reduce protein synthesis

• They signal neighboring cells to undergo apoptosis

• Activate immune cells

What is programmed cell death?

Apoptosis

• they do not lyse so they do not spread the virus

Why are viruses special?

In order to live, they need to be inside a live cell.

• They cannot live on their own

What is the goal of a virus?

To change the cell machinery of the host cell

What type of pathogen most strongly induces interferon production?

Viruses

Which cells secrete interferons?

Virus‑infected cells.

What is the complement system?

A defensive system of plasma proteins that are activated by microbes and promote the destruction of the microbes

• A series of plasma proteins that form a cascade to destroy pathogens.

Where are complement proteins made?

In the liver

• then dumped into the blood stream

The cascade reaction in a complement system consists of?

30 - 60 Plasma Proteins

The complement system is the bridge between?

Innate and adaptive immunity

• some pathways belong to adaptive while some belong to innate

Complement proteins are inactive until?

There is an infection

• they become activated

How many pathways does the complement system have?

Three

• Classical

• MB-Lectin

• Alternative

All produce the same result

What best describes the classical pathway?

• Antigen:antibody complexes

• Belongs to adaptive immunity

What best describes the MB-Lectin pathway?t

• Lectin binding to pathogen surface

• Innate Immunity

What best describes the Alternative pathway?

• Pathogen surfaces

• Innate Immunity

All three pathway (Classical, MB-Lectin, & Alternative) of the complement system lead to?

Complement Activation

• When the proteins circulate in the blood in an inactive state are activated due to a pathogen

Complement activation then causes what immune responses?

• Recruitment of Inflammatory Cells

  • Inflammation

• Opsonization of pathogens

• Chemotaxis

• MAC formation

• Killing of pathogens

  • Cytolysis

  • Elimination of immune complexes

What is MAC?

Membrane attack complex

• made of complement proteins

What is opsonization?

Complement protein binds to pathogen to enhance phagocytosis.

• phagocytic cell can identify pathogen easier due to complement protein

What is inflammation in terms of the complement system?

Complement system releases chemicals that activate and attracts various cells of innate immunity (Mast cells, basophil, neutrophil, macrophage, etc.)

• causes inflammation due to mast cells and basophils and complement proteins

What is cytolysis?

Complement system creates MAC to lyse the cell

• MAC proteins attach to cell and make little holes in them, which makes the cell membrane porus which causes it to lyse and die

What is elimination of immune complexes?

The complement protein finds an antigen-antibody complex and binds to it, then the other end binds to a red blood cell

• Red blood cells usually go to the liver and spleen to recycle

• when the red blood cells get recycled, it forced the antigen, antibody, and complement protein to leave the body

• Whenever RBC gets recycled, it kills the antigen

The classical pathway, used during adaptive immune responses, occurs when?

C1 reacts with antibodies that have bound an antigen.

Fragment from C5 joins C6, C7, C8, and C9 to form?

Membrane attack complex

• makes a whole in pathogens plasma membrane which causes it to lyse

C3 attracts?

Phagocytes to infection site

C1 binds to an antigen-antibody complex on an invading pathogen, causing?

Complement components C2 and C4 to split in two

What is an antigen and anti-body complex?

When antibody binds to antigen

What white blood cells are the “foot soliders” that are the first to arrive at the site of infection?

Neutrophils

What white blood cells are the “big eaters” and are the clean up crew that arrives at the injured or infected scene late and stays longer

Macrophages

What white blood cells are engaged in chemical warfare that causes inflammation?

• Basophils

• Mast cells

What serve as security guards that search and destroy unwanted cells?

Natural Killer cells

What are the heavy artillery cells that take on the “big guys” (parasites)

Eosinophils

What cells are phagocytic?

• Neutrophils

• Macrophages

• Basophils

• Mast cells

• NK cells

• Eosinophils