Immunity Immunity ability of an organism to resist

Immunity Ø Immunity: ability of an organism to resist disease. Ø Homeostasis: the tendency of the body to maintain stability while continually adjusting to conditions that are optimal for survival. Ø Homeostatic mechanisms are necessary for the body to regain its balance when disease or injury occurs and to maintain that balance if it is to remain healthy. Ø Antigen: any substance that elicits an immune response. Ø Antibodies: made in response to specific antigens; can inactivate the antigen that triggered the antibody formation.

The Body Fights Back: 2 Ways Ø Surface Barriers Keep Intruders Out • Prevents entry of antigens inside our body • Skin, Mucosa Ø Response Against Antigens: • Cell Mediated Immunity: Cell activates itself to defend against the attack • Humoral Immunity: Cell produces antibodies carried in blood to combat the intrusion

Declaring War on Invaders Ø The Antigen The Enemy Invader • Usually a bacteria or virus • Comes in many different forms and attacks the body

The Warriors Ø The Macrophage Body's Radar l Type of cell normally present in the blood l Detects the enemy

The Warriors Ø The T-Helper Cell Communication Link Ø Communication Link Between the body's macrophages and Bcells

T-Cells in Action Virus

The Warriors Ø The B-Cell The War Factory l Produces antibodies custom tailored for the type of enemy antigen

B-Cells in Action Virus

The Warriors Ø Antibodies Antigen Busters l Designed to seek and destroy the specific enemy antigen Ø Complement Support Troops l Assists the antibodies to neutralize the enemy antigen

Humoral Immunity Since antibodies circulate through the humours (body fluids), the protection afforded by B cells is called humoral immunity. Structure of antibodies (Y-shaped proteins)

So what does an antibody do? 1. Binds to molecules (antigens) on the surface of invading organism. 2. Inactivates or renders the microorganism susceptible to destruction by the immune system.

The War Immune Complex: When antibodies and complement attack the antigen, an immune complex is formed. Polymorph : Disposal Unit. Detects the immune complexes and removes them T-Suppressor Cell: Another Communication Link Signals to the B-cell to stop making antibodies once the antigen has been destroyed

Review 1 Ø What is the enemy called that invades the cell? Ø What keeps intruders out? Ø What are the two kinds of immunity?

Surface Barriers or Mucosal Immunity ØSkin ØCilia ØTears, Saliva, Urine. ØSticky mucus ØStomach: ØHydrochloric Acid

Analogy Ø Suppose the classroom is a body. Ø All students are cells. Ø Rats are Antigens. Ø Doors and Windows prevent them from entering - Surface Barriers. Ø Some of you Tough ones (T-cells) will capture the rodents - Cell-mediated Immunity. Ø Some of you Brainiacs (B-cells) will call pest control (Antibodies) to capture the rodents – Humoral Immunity.

The Ultimate Battlefield : Blood BLOOD: It is the place where the antigen and the antibody/T-cells collide. Blood cells= RBCs + WBCs + Platelets.

Normal Blood Cell Count Type of Cell RBC Men 5 -6 billion cells per Liter of Blood Women 4 -5 billion cells per Liter of Blood WBC 4 -11 billion cells per Liter of Blood Platelets 150 -400 billion cells per Liter of Blood Type of Cell Increase Decrease RBC Erythrocytosis Anemia WBC Leucocytosis Leucopenia Lymphocyte Lymphocytosis Lymphocytopenia Platelets Thrombocytosis Thrombocytopenia

The Cells in Blood Source: National Library of Medicine *Lymphocyte not shown. Looks like a monocyte, except nucleus mostly fills the cell and does not have a notch in it.

The Role of Neutrophils When a wound occurs, neutrophils migrate out of blood to rush to the wound and phagocytize (“eat”) the bacteria. This is what pus is made of. “old” neutrophil surrounded by red blood cells

The Role of Monocytes Eosinophils Turn into Macrophages Attack Internal Parasites Note the notch in the nucleus. Otherwise, it looks like a lymphocyte. Note the red granules in the cytoplasm.

The Role of Macrophages Enter tissue and engulf and then digest cellular debris and microbes Note the irregular cell membrane. These are the largest blood cell, but they migrate out of blood into damaged tissue.

The Role of Platelets Blood Clotting They can clump together to form clots. No role in immunity.

Review 2 Ø What do Macrophages do? Ø Where is the “Ultimate Battlefield? ” Ø What do Platelets do?

Leukocytosis Ø Leukocytosis: white blood cell count increased above the normal range. Ø It is not a disorder or a disease, but a sign of illness. Ø It occurs in response to a wide variety of conditions, including l viral, bacterial, fungal, or parasitic infection l cancer l Hemorrhage (internal bleeding) l exposure to certain medications or chemicals including steroids.

Leukopenia Ø Leukopenia: a decrease in the number of circulating white blood cells in the blood. Ø As white blood cells get “used up” during infection, leucopenia can place patients at higher risk for infection. Ø Causes: l Influenza, typhus, malaria, HIV, tuberculosis, dengue, Rickettsial infections, enlargement of the spleen and folate deficiencies. l chemotherapy, radiation therapy, leukemia , myelofibrosis and anemia. l many common medications like minocyclen.

HIV (Human Immunodeficiency Virus) Ø HIV infection causes AIDS (Acquired Immuno. Deficiency Syndrome). Ø AIDS causes the immune system to fail, leading to life- threatening opportunistic infections. Ø Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Ø The four major routes of transmission are l l unprotected sexual intercourse, contaminated needles breast milk transmission from an infected mother to her baby at birth.

AIDS (Acquired Immuno. Deficiency Syndrome) Ø Virus infects vital cells such as helper T cells and macrophages. Ø When T cell numbers decline below a critical level, cell-mediated immunity is lost, and infections with a variety of opportunistic microbes appear.

Cell-mediated immunity Ø It is an immune response that does not involve antibodies, but rather the cells act as the killers themselves. Ø It protects the body by: Ø Activating antigen-specific T-cells that destroy infected cells. Ø Activating macrophages that destroy intracellular pathogens. Ø Activating NK (Natural Killer) cells that release a protein that kills the target cells

Review 3 Ø What is Leukopenia and what does it cause? Ø What immune response does not involve antibodies?

Immune System Research How do they test for antibodies?

ELISA TEST Remove blood cells and use the fluid (serum) to test for presence of antibody. A. Place target sample on a support B. Add serum that has antibody against antigen being tested for. Antibody, if present, binds the antigen. C. Add a second antibody (that was separately developed to react with the antibody/antigen complex in step B) binds it to the complex. Second antibody was also prepared with an enzyme attached to it. D. This new complex is made visible by reacting it with an enzyme that converts it to a colored compound that you can see.