Immune/Lymphatic System

I. Brief history of disease A. Disease: any change, other than injury, that disrupts the normal functions of the body. –1. Inherited –2. Environmental –3. Infectious agents (pathogens- “sickness maker”)

B. Spread & the Fight Against 1. Fight a disease by avoiding it 2. Understand disease so you are better able to prevent it. 3. Remove vectors: organisms that carry disease causing agents. –a. Ex: mosquito & spray insecticides 4. New Drug Treatments: Antibiotics-work by killing bacteria BUT not the host cells.

C. For thousands of years people did not know what caused illness –1. Curses, evil spirits, etc –2. Mid 19 th century Louis Pasteur & Robert Koch concluded that disease was caused by microorganisms or germs called “Germ Theory of Disease”

II. Body Defenses A. The body is constantly in contact with bacteria, fungi, and viruses B. Because of our two defense systems –1. Nonspecific defense system –2. Specific defense system

C. Nonspecific Body Defenses 1. 1 st line of defense –a. Intact skin & production of sweat, body oils & Mucous –b. Chemicals produced by the body (very low pH in the stomach, slightly lower pH in urine and female reproductive tract.)

2. 2 nd line of defense a.Defensive Cells- cells that roam the body engulfing (phagocytosis) intruder cells b.Natural Killer Cells –i. can recognize invader cells based on chemicals on cell membrane (cancer and viral cells) before specific defense kicks in. Figure 12.7a

c. Inflammatory Response –i. Triggered when body tissues are injured –ii. Produces 4 cardinal signs Redness Heat Swelling Pain –iii. chain of events which lead to protection and healing

Steps in the Inflammatory Response pg 797 iv. Cells release histamine (protein) –Allow: Blood vessels to dilate, become more permeable & allow more Defense cells to the wound area Figure 12.8

D. Specific defense system 1. Each type of invader has a specific defense –a. A.K.A. “immune system”

E. Antigens (Nonself) 1. Any substance capable of activating the immune system and provoking an immune response 2. Examples of common antigens –a. Foreign proteins –b. Pollen grains –c. Microorganisms

F. Self-Antigens 1. Our cells have many surface proteins thus our system can recognize itself 2. Our immune cells typically do not attack our own cells (If it did that would be a homeostatic imbalance!) 3. BUT each persons surface proteins are unique so, our cells in another person’s body can trigger an immune response because they are foreign –a. Restricts donors for transplants –b. Can cause miscarriage

G. Specific Defense: The Immune System – Third Line of Defense 1. Antigen specific – recognizes and acts against particular foreign substances 2. Systemic – not restricted to the initial infection site, covers the entire body 3. Has “memory” – recognizes and mounts a stronger attack on previously encountered pathogens

H. Cells of the Immune System 1. Lymphocytes –a. from stem cells in the red bone marrow –b. B lymphocytes create antibodies & memory cells –c. T lymphocytes specialized in the thymus gland 2. Macrophages –a. Large cells that eat other invader cells –b. Become widely distributed in lymphoid organs

J. Types of Immunity 1. Antibody-mediated immunity (HUMMORAL) –a. Cells (lymphocytes) produce chemicals (anti- bodies) to mark antigens for disposal. 2. Cell-mediated immunity –a. Cells target virus infected cells directly

K. Antibody-Mediated Immune Response (HUMMORAL) 1. B lymphocytes with specific receptors bind to a specific antigen 2. The binding event activates the lymphocyte to clone itself 3. A large number of clones are produced

4. Most cloned B cells become plasma cells –a. Produce antibodies to mark antigens 5. Some B cells become long-lived memory cells –a. Ready to respond to subsequent exposure to same antigen.

L. Antibodies (Immunoglobulins) 1. proteins secreted by cloned plasma cells 2. Carried in blood 3. Bind to specific antigens to… Figure 12.15a

4. inactivate antigens by: –a. prevent antigen from attaching to anything else –b. Mark it for death, phages know to kill it.

M. Cell-Mediated Immune Response 1. Many different types of T cells which directly attack invaders. 2. macrophage cells “eat” invaders –a. Pieces of the invader are displayed by macrophage. 3. T cells bind to these macrophages antigens and become…

4. Helper T cells: attract natural killer cells. They can ALSO activate B cells 5. Killer T Cells are very effective in killing. Because they actively seek out the invader. –a. Killer T makes organ transplant difficult  –b. Rejection of organs –c. Suppression drugs are taken for life

N. T Cell Clones 1. Suppressor T cells –a. Once the invader has been removed chemicals are released to suppress the activity of T and B cells –b. Stop the immune response to prevent uncontrolled activity

O. Secondary Response to an invader 1. Memory cells are long-lived 2. A second exposure causes a rapid response 3. The secondary response is stronger and longer lasting Figure 12.13

A/B Day 3/11-3/12 Lecture on Immunity & disorders of immune system & Lymphatic system Worksheets on above Wednesday- lecture on Antibiotics & resistance and Vaccine Debate Thurs/Fri- LAB? TEST next week either C Wednesday or A/B Thurs/Fri. T.B.D.

P. Immunity 1. Active: a. Your B cells actively encountered antigens and produce antibodies 2. Passive: a. Antibodies are obtained from someone else b. B cell memory does not occur because protection “borrowed”; your body did not create Figure 12.14

Q. Disorders of Immunity: 1. Allergies (Hypersensitivity) –a. Abnormal, vigorous immune responses 2. Autoimmune Diseases: T cells attack its own tissues Examples –a. Multiple sclerosis – white matter of brain and spinal cord are destroyed –b. Juvenile diabetes – destroys pancreatic beta cells that produce insulin –c. Rheumatoid arthritis – destroys joints

AIDS Acquired Immune Deficiency Syndrome Caused by HIV (Human Immuno Deficiency Virus) Virus attacks the Immune System cells, knocks out the Immune System and the person dies of other infections.

Unique Incurable (?), high mortality, quickly spread, no vaccine. **The combination is RARE in this technological age. Spread through intimate contact w/ an infected person –THIS is a limiting factor! Think what could happen if it was airborne  –UNFORTUNATLY a person can carry and transmit HIV for years before symptoms arise

How it’s contracted 1 in 1000 chance of contracting HIV during unprotected heterosexual sex (of any kind). –Higher for some areas of the country and higher for some groups of people Unprotected sex (of any kind) is the most common. You can also be exposed… –Sharing needles –Blood transfusion (rare if blood is tested) –Mother/baby –Breastfeeding

Not transmitted through… Sweat, saliva, tears have small traces: There is a SLIGHT possibility through kissing. Insects Environment: HIV is fragile and dies quickly outside of the body. –Same toilet use –Touching, hugging, hand shaking –Sitting next to or where someone has been sitting

How it works HIV infects the helper T cells & the body loses it’s specific defense! AND HIV can mutate making it hard to treat with drugs.

Life Cycle All viruses require a host cell to live and replicate HIV attacks the helper T cell which reduces the number of helper T (hT) cells until the person has AIDS –Usual amount= 1million hT cells in 1 ml pf blood –AIDS= > 200,000 hT cells per 1 ml blood –Takes 2-15 years

No one dies from HIV/AIDS They die from infections that their body can no longer fight off. Can be the common cold to a minor infection.

III. Lymphatic System Anatomy Consists of two semi-independent parts –Lymphatic vessels –Lymphoid tissues and organs Lymphatic system functions –Transport fluids back to the blood –Play essential roles in body defense and resistance to disease

Organs of the Immune System Skin- Mucose Membranes- Once inside…

Once Inside… Lymph System –When the Dr. checks your neck they are feeling for swollen lymph nodes. Lymph system follows the pattern of the circulatory system BUT it is not pressurized, it is passive. –Fluid diffuses into the lymph system and is “pushed” by normal body and muscle motion to the nodes.

Lymph Fluid? Clear fluid that bathes the cells in nutrients. –interstitial fluid & blood plasma are similar Also carries away waste and proteins and random bacteria through the lymph vessels to the lymph Nodes.

Lymphatic Vessels Figure 12.2

Lymph Nodes Filter lymph before it is returned to the blood Defense cells within lymph nodes –Macrophages present to B & T cells here These nodes swell during some infections due to filtration (full of dead invaders and defense cells)

Lymph Node Structure Figure 12.4 Most are kidney-shaped, less than 1 inch long

Other Lymphoid Organs Several other organs contribute to lymphatic function –Spleen –Thymus –Tonsils –Peyer’s patches Figure 12.5

The Spleen Filters blood & Destroys worn out blood cells Forms blood cells in the fetus An adult can live w/o the spleen, but you’ll be sick more often

The Thymus Located low in the throat, overlying the heart Functions at peak levels only during childhood to produce/mature t-cells.

Tonsils Small masses of lymphoid tissue around the back of the throat Trap/remove bacteria and other foreign materials & give immune system a “heads up”. Tonsillitis is caused by congestion with bacteria –They are no longer removed because we now understand their purpose is to become infected (rather than the whole person)

Peyer’s Patches Found in the wall of the small intestine Resemble tonsils in structure Capture and destroy bacteria in the intestine (same idea as tonsils) Appendix?