Directions: Define key science terms relating to immunology and physiology using contextual clues from “Transplant tolerance.” Consult an outside resource if necessary.

Word bank and definitions by science subtopic:                   

Immunology

What is the immune system, and what does it do?
The immune system is a collection of cells that help the body fight off infections and diseases. The immune system recognizes and attacks pathogenic organisms or cells that have invaded the body, as well as the body’s own cells that become cancerous. 

What is an allergic response?
An allergic response is when the immune system reacts to a normally harmless substance, such as a particular food, pet, plant or drug. Untreated, a particularly severe allergic response can lead to death.            

What is transplant rejection?
Transplant rejection occurs when the immune system recognizes transplanted organ as foreign and not belonging to the patient. As a result, the immune system attacks and kills the transplanted cells, impairing or destroying the function of the organ.            

What is an autoimmune disease?
An autoimmune disease is inflammation caused by a person’s immune system attacking that person’s own body. This inappropriate reaction can cause disease instead of curing it. Autoimmune diseases can be quite severe and hard for doctors to treat. They include rheumatoid arthritis (affecting joints such as knees), multiple sclerosis (targeting nerves and muscles), Crohn’s disease (affecting the gut), psoriasis and lupus (affecting skin) and the type of diabetes that typically develops in young children. In all of these cases, the immune system generates out-of-control inflammation.

What is immune deficiency?
Immune deficiency is when part or all of the immune system is too weak to fight off infectious diseases or cancerous cells. Some immune deficiencies are inherited. Others are caused by viruses, like HIV. Immune suppressing drugs, which can help prevent the immune system from attacking a transplanted organ, also cause immune deficiency.        

What are antibodies?
Antibodies are proteins that immune cells in the body produce and release into the blood. Antibodies bind to very specific surface features on other molecules or on cells. The body produces antibodies when it encounters some foreign material, called an antigen. Antibodies lock onto antigens as a first step in disabling the germs or other foreign substances that were the source of those antigens.

What are B cells?
B cells are a type of small white blood cell that produce antibodies. In some cases, the antibodies remain attached to the surface of the B cells and are used as sensors. In other cases, the antibodies are released to float around on their own.         

What are HLAs and MHCs?
Human leukocyte antigens (HLAs) and major histocompatibility complexes (MHCs) are cell-surface proteins that function like bar codes to help the immune system identify your cells versus foreign, cancerous or infected cells.            

What are T cells?
T cells are a family of white blood cells, also called lymphocytes, which are primary actors in the immune system. They fight disease and can help the body deal with harmful substances. They use cell-surface receptors as sensors to examine other cells’ MHCs and any proteins that MHCs may be holding.            

What are cytotoxic T cells?
Cytotoxic T cells are immune cells that kill other types of cells that may be a threat, including foreign cells, cancer cells and cells infected with a virus. Cytotoxic T cells identify target cells by the MHCs on their surfaces.            

What are macrophages?
Macrophages are a type of white blood cell that surrounds and kills microorganisms, removes dead cells and stimulates the action of other immune system cells.

What are helper T cells?
Helper T cells are a type of immune cell that stimulates cytotoxic T cells, macrophages and B cells to make immune responses.            

What are regulatory or suppressor T cells?
Regulatory or suppressor T cells help to tell the rest of the immune system when not to react to something.            

What are memory B cells and memory T cells?
Memory B cells and memory T cells remember specific threats that the immune system has encountered before. These cells spring into action if that threat arises again. That is why you are immune to most specific infectious diseases that you have had before, or against which you have been vaccinated.           

What are vaccines? A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease. The injections used to administer most vaccines are known as vaccinations.           

What are natural killer (NK) cells?
NK cells are a type of immune system cell that kills other types of cells in the body that are missing MHCs. Cells that have removed or buried their own MHCs may be trying to hide that they are foreign, cancerous or infected.

What are mast cells?
Mast cells are a type of immune system cell uses antibodies made by B cells as sensors to detect foreign substances. If mast cells find something foreign, they release signals that cause inflammation and summon other immune cells.     

What are phagocytes?
Phagocytes are cells that eat the body’s own cells that have died, foreign cells, the remains of foreign cells or other debris. They function both as a part of the immune system and as a trash collection system.

 

Anatomy and physiology

What does the liver do, and what problems can happen if it is not functioning properly?
The liver is the chemical engineering department for the whole body. It can store fat and sugar as energy, break down harmful substances for excretion by the body, and secrete bile — a greenish fluid released into the gut, where it helps digest fats and neutralize acids. If the liver isn’t functioning properly, chemicals can build up in the body and become toxic.  

What does the pancreas do, and what problems can happen if it is not functioning properly?
Part of the pancreas produces digestive enzymes that help break down food in the stomach and small intestine. An especially important part of the pancreas secretes the hormones insulin and glucagon as well as other molecules that break down food in the gut and help keep blood sugar concentrations at a healthy level. The most common problem with the pancreas is that some or all of those hormone-producing cells die off, resulting in uncontrolled blood sugar — a disease called diabetes.          

What do the kidneys do, and what problems can happen if they are not functioning properly?
The kidneys filter out toxins and other molecules from blood as it circulates and produces urine to remove excess liquid from the body. If the kidneys are not functioning properly, blood pressure and volume can become too high, and toxic molecules can rapidly accumulate in the body.           

What does the spleen do, and what problems can happen if it is not functioning properly?
The spleen stores blood, filters old or damaged red blood cells as well as viruses and bacteria out of circulating blood, and creates various immune system cells including B cells. If the spleen is not functioning properly, it can cause immune deficiency or become infected and burst.       

What do the lungs do, and what problems can happen if they are not functioning properly?
The lungs bring air in and out of the body. As the lungs expand, they provide oxygen from the air to the capillaries to oxygenate the blood. As the lungs compress, the exchanged carbon dioxide waste is pushed out during exhalation. If the lungs are not working properly, the body may not be able to get enough oxygen to sustain itself properly.         

What does the heart do, and what problems can happen if it is not functioning properly?
The heart circulates blood throughout the body. Blood facilitates all of the essential processes that the body needs to function. If the heart is not working properly, one serious problem is that some or all tissues and organs may not get enough blood and oxygen.           

Discussion beyond the article: The article presented a timeline called “Second chances” with a few of the major milestones in the history of organ transplants. As an optional activity, students can partner up to search the Science News archive for additional articles about organ transplants. After groups have read and summarized their articles for their classmates, the class can create a timeline showing the history of organ transplants. Students should include milestones from the “Second chances” timeline in their class timeline.

Some related Science News article examples that could be used for the timeline:

“The organ transplant odyssey,” Science News, October 1, 1983

Type of transplant: Cyclosporine and review of organ transplants from 1960s to date

“New hand, same brain map,” Science News, November 8, 2008

Type of transplant: Hand transplant surgery

“A dash of marrow helps kidney transplant,” Science News, March 7, 2012

Type of transplant: Kidney and bone marrow transplants

“The first penis-scrotum transplant is the latest to go beyond lifesaving” Science News, April 24, 2018

Type of transplant: Penis-scrotum implant on a 2018 veteran