The IMMUNE System

Purposes of the Immune System

1. Return tissue fluid to the blood stream

2. Fight infection

• Four basic types of germs: Viruses, Bacteria, Protozoa, Fungi

Lymphatic System Made up of both innate and acquired immune

systems

Organs – Macrophages wait to destroy prey!!

•Lymph nodes, tonsils, adenoids, appendix, spleen

• Lymphocytes come in three flavors, B-cells, T-cells, and Natural Killer (NK) cells. B-cells can become plasma cells and produce antibodies. T-cells exist in 2 forms, helper T-cells and killer T-cells. Helper T-cells are a bit like antibodies and help tag bacteria for destruction. Killer T-cells and NK cells do exactly what it sounds like they do -- they kill bacteria. Monocytes are big and slow Pacman-like cells that eat other cells whole. It can take 3-5 days for these bad boys to arrive on the scene, and so the immune system has neutrophils, which are smaller and stealthier. Basophils are basically wimps. Eosinophils fight crime in the form of parasitic infections.

T and B cells

• T Cells – made in marrow, but develop and reside in thymus–

• B Cells – made in marrow

Humoral Immunity—depends on antibodies (proteins made by B-cells)

This refers to a response by certain cells of the immune system (B cells) which have the ability to make what are called antibodies. Antibodies are proteins which float around in the blood and have a particular ability to bind to a foreign protein.Depending on the features of this foreign protein, antibody binding to it will have numerous possible effects.

-ex- would be antibodies which can recognize proteins on the surface of invading bacteria. If antibody coats the surface of the bacteria, the cell will more easily recognize that the bacteria is foreign, and try to destroy it.

-ex - is antibody which can recognize a certain toxin produced by bacteria and neutralize its toxic action. An example of this is antibody against tetanus toxin. If we get infected with the bacteria which causes tetanus, we can usually handle the bacteria infection and rid the body of the pathogen. The problem is that the bacteria can quickly make a potent toxin which can make us very sick. The vaccine is actually an inactive form of the toxin. This antibody floats around our bodies for years, until the day we get infected by the tetanus bacteria. As soon as the bacteria makes the toxin, the antibodies bind it, and prevent any terrible consequences.

Cellular Immunity—depends on T-cells

-Viruses are incapable of replicating on their own, and so they must invade cells of our body and hijack the cell's machinery to replicate. -Cell mediated immunity is the type of response that can allow cells of our immune system (T cells) to recognize which cells in our bodies are virally infected. -The T cells seek out these cells, and destroy them, thereby killing the virus contained within them. -Once all of the infected cells are wiped out, there is no more virus left in our bodies. By generating a response to the virus, our T cells end up with what is called memory. Next time we are infected by the same virus, certain T cells remember seeing it before and can respond quicker and more explosively.

This is the basis behind vaccination for certain diseases.

One thing to note is that some viruses place their genetic material into the genetic material of the cell and hide out. T cells may not recognize that this cell is infected, and may pass over it when seeking out infected cells. At a later time point, using the genetic material which the virus deposited in the cell at an earlier time, the cell may begin producing new virus. Now the cell should be recognized by T cells, and destroyed.

Two Types of Disease

NonInfectious DiseaseAKA Noncommunicable

AKA Noncontagious• Diseases NOT caused by

germs cannot be transmitted from person to person.

• Diseases caused by genetics or lifestyle choices.

• EX: Most cancers, heart disease, hemophilia, etc.

Infectious DiseaseAKA Communicable

AKA Contagious

• Diseases caused by germs.

• Can be transmitted from person to person.

• EX: HIV, STDs, the Flu, the Cold, Ear Infections, Malaria, Hepatitis, Tuberculosis, etc.

Two Types of Immunity

Passive ImmunityImmunity that does

not require an immune

system response, but

antibodies are otherwise acquired against a

particular antigen.

Genetic Immunity

Breastfeeding

Immunity is the inability of a pathogen to infect an organism. Active Immunity

Immunity occurs as a result of an immune system response to

foreign antigens circulating through the body.

Vaccination

Illness

How do Pathogens Enter the Body

• Vectors are carriers of pathogens—insects • Importance of skin—Langerhans cells mixed

with the melanocytes alert WBC when pathogens attempt to enter.

• Sebum (oil) contains antimicrobial chemicals.• Mucous Membranes (entrances to the body—

mouth, eyes, anus, etc) contain mucus to trap and enzymes that break down pathogens.

• Once a pathogen has entered the body it must also survive, the lymphatic system, the kidneys, and circulating WBC before it can infect.

How Does the Immune System Work?

• Inflammatory Response—body’s attempt to prevent an infection when a pathogen enters or when tissues are damaged.

1. Release of histamine—causes blood vessel walls to spread so that WBC and fluids can move towards the site of infection.

2. Swelling

3. Itching

4. Redness

5. Warmth

How Does the Immune System Work?

Normal human body temperature is 98.6oF or 37oC.

When pathogens enter the body the hypothalamus may release chemicalsto increase the body’s core temperature.

Low fevers ~100oF a) increase the maturation rate of WBC b) reduce the reproduction rate of pathogens

High fevers 103o or highera) are beyond control of the hypothalamusb) may cause seziures, brain damage or death

How Does the Immune System Work?

• Antigens are substances or molecules that, when detected by WBC, trigger an immune response.

• ALL cells have markers outside their cell membrane, if those markers do not match the ones that are supposed to be present, the immune system will act.

• Vaccines are a way of introducing an antigen without the potential of infection. A vaccine, or immunization, introduces enough or a foreign cell to trigger a small immune response that if the REAL antigen presents itself, the immune system will be ready.

Allergies• Abnormal sensitivities to antigens (allergens)

– Histamine – chemical in body for response– Antihistamines – blocks histamines

• Anaphylactic shock – very sensitive and have a deadly high amount of histamine released at high rate.

Malfunctions of Immune system• Autoimmune diseases – immune systems

is confused or misdirected.– Lupus, MS, Rheumatoid Arthritis, diabetes

• Immunodeficiency diseases- missing an entire component to

immune systemBubble boy