Membranes in the Immune System

By Lauren, Olivia, Milly and Lindsay

There are Three Lines of Defense

1st Line of Defense -- Barriers at Surface (6)

Keeps pathogens out of the body (nonspecific)→ Skin: Low pH, little moisture, thick layers of dead

skin cells→ mucous membranes: Contain lysozyme (ex. Lungs)→ Lysozyme and other substances in tears, saliva, and

gastric fluid→ urination and diarrhea flushes pathogens away from

the body

2nd Line of Defense -- Nonspecific Responses (5, 6)

1) Inflammation: increase in blood flow to the affected area (= painful) (5)a) White blood cells (neutrophils, eosinophils, basophils)b) Phagocytic cells: macrophages (which also takes part in the specific

immune response)c) Complement proteins in the blood, including blood- clotting proteins,

other infection fighters.2) Organs with pathogen-killing functions (lymph nodes)3) Interferon-proteins released by cells, ramps up

immune system(6).4) Fever-temperature too hot for pathogens

major lymph node areas

White Blood Cells Destroy Microbes (5)Three white blood cells: neutrophils, eosinophils, basophils react quickly.

● Neutrophils=most abundant white blood cell, eat bacteria.● Eosinophils=secrete enzymes that create holes in parasitic worms● Basophils=secrete histamine and other substances ● Macrophages= white blood cells, called “big eaters,” engulf and

digest foreign agents + clean up damaged tissues. ● Mast cells= (not a white blood cell) reside in connective tissues

and function like basophils, they synthesize and release histamine○ histamine = a chemical signals that trigger vasodilation○ vasodilation= an increase in a blood vessel’s diameter after

smooth muscle in its wall has relaxed, letting plasma proteins to “leak” easily out of the blood in the injured site

Plasma Proteins In the Blood (5)A protein attaches to an antibody or the pathogen itself. Protein becomes activated

Activated: it begins producing many other complement proteins and these are assembled into attack complexes.

Attack complexes attack the lipid membrane or envelope of the pathogen, causing large pores to form. Lysis, a major structure disruption, occurs=death. Also on pg 691 in textbook

Phagocytosis (5)

Phagocyte: A type of cell (macrophage) that can eat pathogens that pass into body tissues

→ pathogen infected cell signal the phagocyte to destroy it (mercy killing)→ Phagocyte attaches to the pathogen using their surface receptors→ The phagocyte then engulfs the pathogen into a vacuole, known as a

Phagosome

→ Lysosomes fuse with the phagosome, forming phagolysosomes→ Inside the phagolysosome, the pathogen is killed

→ Takes some of the remains and presents it on its surface for the specific immune response http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

3rd Line of Defense -- Specific Immune Response

T Cells● Hangs out in organs, then rushes to the

infected area when notified (7)● Uses MHC (Major Histocompatibility

Complex) Proteins to determine whether a cell is self or pathogen(6).

B Cells● Fights pathogens in bloodstream (7)● Forms in the bone marrow and also

matures in the bone marrow● Coated in thousands of antibodies that

detect and kill one specific pathogen by attaching to the antigens located on it’s surface. An antigen is any molecular configuration that triggers formation of lymphocytes. They are usually found on the surface of invaders.(6,7)

When a B-cell finds and attaches to a recognizable antigen, it copies itself so that the body can come into contact with and kill the antigen more quickly. (7)

T Cell interacting with a macrophage

T Cells

Helper T Cells (6)● Phagocytes present pieces of the pathogens they gobbled. The T cells examine these pieces by attaching

themselves to the presented antigen and communicating with the antigen-presenting cell● The Helper T cell first sends out chemical signals to tell nearby white blood cells about the pathogen, then

makes a LOT of copies of itself. (2)● These copies fall into two categories: Effector T Cells and Memory T Cells

o Effector T Cells secrete protein signals to tell other white blood cells to come to the infected area and fight.

o Memory T Cells remember the intruder so that the pathogen can be identified faster in future cases“Natural Killer” T Cells or Cytotoxic T Cells(6,7)

● These cells kill cells that contain pathogens by secreting perforinso Perforins are proteins that form holes in the plasma membraneo chemicals are inserted through these holes that cause the cell to commit apoptosiso Cytoplasm and organelles also leak out through the holes, which also will kill the cell

Killer T cells interact with a cancer cell

B CellsAntibodies:

● Antigen-binding protein complexes secreted from plasma/effector B-cells (1,6,7)● Two Primary Functions

o White blood cells and invaders both hold a negative charge, so they repel from one another. The antibodies, however, attach to the surface of an invader and neutralize the charge. (1)

o Antibodies can also activate Phagocytes, which makes them more active in seeking out invaders and killing the invaders more quickly (1)

● Antibodies are powerless in actually penetrating pathogens, but help white blood cells to complete phagocytosisPlasma/Effector Cells(7):

● Created by B-cells once they are attached to a pathogen.● Creates Antibodies. (Around 200 antibodies a second!)

Memory Cells(7) :● Created by B-cells once they are attached to a pathogen.● Majority of B-cell clones are memory cells● Holds memory of the antibodies against a pathogen for future use

Creative Activity

Round 1: In a group of 8 people, each person receives a card. One person will receive a joker card, and will be the “pathogen.” Everyone shakes hand with each other, and the pathogen will scratch the person’s hand, and the person whose hand was scratched will “die” after they shake 3 more people’s hands. To win the game, people will guess who the pathogen is, and if they guess it wrong they die.

Round 2: A new person will be introduced. This new person will be a helper T cell. They will go around asking to see each person’s card (MHC Protein) to try to identify the pathogen (the person with the joker).

Useful Video Links

1) Immune Cells in Action: http://www.pbslearningmedia.org/resource/tdc02.sci.life.stru.immune/immune-cells-in-action/

2) Immunity and vaccines: http://www.pbslearningmedia.org/resource/nvvs-sci-immunity/immunity-vaccines/

Sources1) "Antibodies." Novimmune. Novimmune, Web. 17 Nov. 2014.

<http://www.novimmune.com/science/antibodies.html>.2) "How T Cells Work." YouTube. Adaptive Biotechnologies Corporation, 27 Dec. 2011. Web. 17

Nov. 2014.3) "Immune System." Immune System. N.p., Web. 16 Nov. 2014.

<http://www.austincc.edu/apreview/EmphasisItems/Inflammatoryresponse.html>.4) Khan, Salman. "B Lymphocytes (B Cells)." Khan Academy. N.p., 18 Feb. 2010. Web. 17

Nov. 2014.5) "Phagocytosis." Animation: Phagocytosis. McGraw-Hill Higher Education, 13 Nov. 2014. Web.

17 Nov. 2014. <http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/

animation__ phagocytosis.html>.6) Starr, Cecie, Ralph Taggart, and Lisa Starr. "Immunity." Biology: The Unity and Diversity of Life.

Australia: Brooks/Cole, 2001. 689-707. Print.7) "Your Immune System: Natural Born Killer - Crash Course Biology #32. “YouTube. Crash

Course, 3 Sept. 2012. Web. 17 Nov. 2014.