Name ______

Immune System – 20 Informal Points

Introduction

In this unit, you have taken a look at the barriers, skin and bone, and accessory organs and secretions that protect the body from injury and initial invasion by pathogens. Now you are going to take a deeper look at the body system that functions to drain and distribute fluid in the body, and to protect the human body against specific invaders – the lymphatic and immune system.

When you think of transportation of fluid around the body, you probably think of the network of blood vessels in the circulatory system. But the body has another transportation system – the lymphatic system. The lymphatic system consists of organs, ducts, and nodes and transports a watery clear fluid called lymph. Up to three liters of fluid remain behind in the tissues and must be returned to the blood each day. Lymph vessels interact with the circulatory system to drain this fluid from your cells and tissues. Lymph also distributes immune cells around the body. White blood cells called macrophages and lymphocytes, that are also found in the blood, form the body’s immune system – your most powerful defense weapon. These cells initiate highly specific responses directed against particular microbes, such as viruses or bacteria or abnormal cells, such as cancer cells, and protect the body while it is under attack.

In PBS, you learned that human blood contains three main cells or cell fragments. Red blood cells help transport oxygen around the body. Platelets assist in protection by helping your blood clot. But it is the white blood cells that really function to keep you well. Your body’s immune system relies on special white blood cells to pinpoint and destroy microbes that may make it through your body’s non-specific defenses. You have been introduced to antibodies, special proteins that can target and inactivate specific antigens. Antibodies are one of your body’s main defenses. These Y- shaped proteins are created by the white blood cells and circulate in your blood and lymph. Specific antibodies are produced when an unwanted antigen enters the body. The antibodies work to disable these invaders and target them for destruction.

Conclusion Questions

  1. Why is red bone marrow considered part of the immune system?

The vast majority of lymphocytes (T-Cells and B-Cells) are manufactured in the red bone marrow.

  1. The walls of lymph vessels are extremely thin. How does this structure relate to function?

Thesevesselsare closed at their ends and have verythinwalls that allow interstitial fluid to flow into the capillaryvessel. Once the fluid enters thelymphcapillaries, it is calledlymph.

  1. Since movement of the lymphatic fluid is not fueled by a pump, such as the heart, how do you think this liquid is propelled around the body? (HINT: Think back to some of the features of veins that helped blood fight back to the heart.)

Lymph is a fluid. It flows through the lymphatic vessels by one way valves whichallows lymph move way through lymphatic system. Muscle movement helps propel the lymph through the vessels.

  1. What is the function of the lymph nodes? Why are they often inflamed or swollen when we get sick?

The primaryfunctionoflymph nodesis to harbor the body's disease-fighting cells. Any infection or virus, including the common cold, can cause yourlymph nodesto swell as the lymph congregates to attempt and kill the infection.

  1. Why do you think the defense mechanisms we have discussed thus far in this unit are considered “non-specific” resistance? What do you think is meant by specific resistance?

Nonspecific immunityis the initialimmunereaction against foreign antigens vianonspecificantibodies andimmunecells. In contrast,specific immunityinvolves the production of antibodies against a particular antigen.

  1. Fill in the table to describe the role each structure plays in the lymphatic system.

Lymphatic System Structure / Function
B-Cells (B lymphocytes) / With the help of T-cells, B-cells make special Y-shaped proteins called antibodies. Antibodies stick to antigens on the surface of germs, stopping them in their tracks, creating clumps that alert your body to the presence of intruders. Your body then starts to make toxic substances to fight them. Patrolling defender cells called phagocytes engulf and destroy antibody covered intruders.
Helper T-cells (T lymphocytes) / Having recognized the invader, different types of T-cell then have different jobs to do. Some send chemical instructions (cytokines) to the rest of the immune system. Your body can then produce the most effective weapons against the invaders, which may be bacteria, viruses or parasites. Other types of T-cells recognize and kill virus-infected cells directly. Some help B-cells to make antibodies, which circulate and bind to antigens.
Macrophages / Macrophages are large, specialized cells that recognize, engulf and destroy target cells.
Mucus / A major function of thismucusis to protect against infectious agents such as fungi, bacteria and viruses since it is sticky and these pathogens stick to it instead of entering the body systems.
Lymph / A colorless fluid containing white blood cells, that bathes the tissues and drains through the lymphatic system into the bloodstream to heal and protect the body.
Cytokines / Cytokinesare cell signaling molecules that aid cell to cell communication in immune responses and stimulate the movement of cells towards sites of inflammation, infection and trauma.
Receptor Proteins / Areceptoris aproteinmolecule that receives chemical signals from outside a cell. When such chemical signals bind to areceptor, they cause some form of cellular/tissue response.
Antibodies /
  1. A blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances that the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood.

Memory Cells /
  1. A long-lived lymphocyte capable of responding to a particular antigen on its reintroduction, long after the exposure that prompted its production.

Plasma Cells / A fully differentiated B cell that produces a single type of antibody. Fights only one pathogen.
  1. How do B-cells and T-cells get their names?

They are named for the place they were discovered.

T cellscome in two different types, helpercellsand killercells. They are namedT cellsafter the thymus, an organ situated under the breastbone.T cellsareproducedin the bone marrow and later move to the thymus where they mature. B Cells are produced and mature in the bone marrow.

  1. Imagine you are exposed to the same flu virus (flu antigen) twice in one year.Name at least two ways in which the body’s response is different each time. Why would the second response to the flu antigen be so different?

During the first exposure a non-specific response will occur to attempt to kill off the pathogen; but the person will be sick. However, due to this initial exposure antibodies will be produced. During the second exposure the antibodies will recognize the antigen and kill off the pathogen either without making the person sick at all or to a much lesser extent.

  1. Given what you now know about memory cells, how do you think a vaccination works?

Vaccines expose a person to a disease without making them sick so that antibodies can be built within the immune system so that if the person is ever exposed to the actual disease they will not truly get sick. Memory cells remember the first exposure (the vaccination) and recognize it as foreign if the person is ever truly infected with the disease.

  1. Sometimes the body can attack its own tissue as if it was foreign. We call these disorders autoimmune diseases. Multiple sclerosis is an autoimmune disease where the body attacks its own myelin. Rheumatoid arthritis is an autoimmune disease where the body attacks the lining of the joints. How do you think each of these diseases would impact the function in the human body? Explain.

Multiple sclerosis destroys the nerve cells causing a person to slowly lose movement. Rheumatoid arthritis affects joint linings, causing painful swelling. Over long periods of time, the inflammation associated with rheumatoid arthritis can cause bone erosion and joint deformity.

  1. What role do other human body systems, such as the digestive system, the integumentary system, and the respiratory system play in protection?

Digestive System – Stomach is acidic to kill bacteria

Integumentary System – Skin serves as a barrier to pathogens

Respiratory – Lined with cilia and mucus to trap pathogens before they enter the body