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Immune system


Front-loading vocabulary

The Immune system is a system of cells and chemicals which recognize, target and destroy pathogens.

Pathogens are organisms that cause a disease in another organism.

RBC = red blood cells, which carry oxygen from the lungs to all body tissues.

WBC = white blood cells, which fight pathogens.

How does the immune system target invaders?

All cells have many different proteins on their cell membranes. Each has their own name and job.

antigens on cell membrane

When we learn how they are recognized by our immune system, we don’t care about their names. We just care whether or not they trigger an immune response. These cell membrane proteins are called antigens.

{ image from http://biginscience.com/big-in-science-articles/2013/12/1/cancer-vaccine-extends-life-for-patients-with-the-most-common-aggressive-form-of-brain-cancer }

When our WBCs “eat” a pathogen (like Pac Man), they then display broken bits of the dead pathogen on their surface. This helps other parts of the immune system recognize the pathogen.

from NobelPrize Org phagocyte antigen


{ from http://www.nobelprize.org/educational/medicine/immunity/immune-detail.html }

Killer T cells

  • Helper T cells can stimulate Killer T cells in response to a particular antigen
  • Killer T cells attack infected body cells and kill them
  • They release enzymes directly into pathogens causing them to lyse and die.

Killer T-Cells


{ from http://kmbiology.weebly.com/immune-response—notes.html }

B-cells bind to antigens

  • Then the B-cells are activated by helper T-cells and divide
  • The cloned B-cells can develop into either Plasma Cells or Memory Cells

Plasma Cells

  • Produce antibodies that are released into the blood stream and tissue spaces
  • Antibodies – Y-shaped proteins produced in reaction to antigens that react with and disable antigens
  • Pathogens covered with antibodies are easier to attack and engulf

B Cells bind to the antigens

Our WBCs that “touch” every cell in our body

If they recognize these antigens as “self” (part of you) then they do nothing. If they do not recognize them , then they are “non-self” (not part of you), and therefore targeted for destruction.

What cells would our WBCs not recognize?
* pathogens
* body cells which could become cancerous.
* On super rare occasions, a terrible mistake is made – and WBCs fail to recognize one of our own normal body cells. This could cause an auto-immune disease.

Many types of WBCs

RBC = carry O2 (oxygen gas) from the lungs, to every tissue in our body

RBC = carry CO2 (carbon dioxide gas) from every tissue in our body, back to our lungs, where we exhale it

WBC = White blood cell, job is to kill anything it doesn’t recognize

Phagocytes, like Pac Man, engulf and digest invaders

Antibodies are “Y” shaped proteins secreted by lymphocytes WBCs. They attach to the antigens on pathogens, targeting them for destruction by other WBCs.

The below text is loosely adapted from http://regentsprep.org/regents/biology/units/homeostasis/disease.cfm


When organisms are exposed to disease, they make specific antibodies. These destroy that pathogen during their first exposure to it. This is called the primary immune response.

Our immune system has a memory. If we’re ever exposed to that same antigen again, we’ll make antibodies rapidly in response to it This is  the secondary immune response.

Vaccinations use dead or weakened pathogens, or parts of them, to stimulate primary immune response

Why dead or weakened? Will not make the organism (us) sick

Because the vaccine has stimulated the immune system, the organism  now has memory. If there is a subsequent exposure, then body quickly fights it off.

Allergies and Auto-immune Diseases

In allergies, the body’s immune system produces chemicals in response to normally harmless substances which do not trouble other individuals. These chemicals make people with allergies feel sick.

In auto-immune diseases, the body’s immune system for usually unknown reasons may attack and destroy some its own cells. Some kinds of arthritis and degenerative diseases result from auto-immune diseases.

Types of immunity


  • Naturally antibodies are transferred from mother to child
    • Through the placenta before the baby is born
    • Through milk after birth
  • Artificial Passive Immunity à injecting antibodies from other animals/humans already immune to disease
    • Snake venom


  • Naturally antibodies are produced during an infection in response to antigens
  • Artificially by vaccines
  • Vaccines à substance consisting of weakened, dead, or incomplete portions of pathogens/antigens that when injected cause an immune response
  • Vaccines produce immunity because it prompts the body to act like it is infected


T-Cells and B-Cells fighting a pathogen

Immune system T and B cells



Ask A Biologist: Viral Attack and Click here to read the comic: “Viral attack!”

The innate and adaptive immune systems



Learning Standards

College Board Standards for College Success: Science

LSH-PE.5.4.3 Give examples, using evidence gathered from print and electronic resources, of genetic diseases (e.g., cystic fibrosis, sicklecell anemia, Tay-Sachs disease or phenylketonuria) that result from mutations to a single gene. Identify, for each example,
the specific type of mutation that causes the change in amino acid sequence and ultimately the change in the protein that is produced.

LSH-PE.5.4.4 Give examples, using evidence gathered from print and electronic resources, of instances when viruses are linked to cancer. Explain, based on knowledge of viral gene insertions and of the relationship among DNA, proteins and traits, how a viral insertion into DNA can cause cancer.

LSH-PE.5.4.5 Give examples, using evidence gathered from print and electronic resources, of the potential of using viruses for curing genetic diseases via gene therapy. Make a claim about, and justify, based on knowledge of viral DNA and viral insertions, why some viruses are appropriate for this application.

Massachusetts Comprehensive Health Curriculum Framework

Students will gain the knowledge and skills to select a diet that supports
health and reduces the risk of illness and future chronic diseases. PreK–12 Standard 4

Through the study of Prevention students will
8.1 Describe how the body fights germs and disease naturally and with medicines and
Through the study of Signs, Causes, and Treatment students will
8.2: Identify the common symptoms of illness and recognize that being responsible for individual
health means alerting caretakers to any symptoms of illness

8.5 Identify ways individuals can reduce risk factors related to communicable and chronic diseases
8.6 Describe the importance of early detection in preventing the progression of disease
Through the study of Signs, Causes, and Treatment students will
8.7 Explain the need to follow prescribed health care procedures given by parents and health care providers
8.8: Describe how to demonstrate safe care and concern toward ill and disabled persons in the family, school, and community

8.13 Explain how the immune system functions to prevent and combat disease

Interdisciplinary Learning Objectives: Disease Prevention and Control
8.a. (Law & Policy. Connects with History & Social Science: Geography and Civics &
Government) Analyze the influence of factors (such as social and economic) on the treatment and management of illness.

Benchmarks for Science Literacy, AAAS

The immune system functions to protect against microscopic organisms and foreign substances that enter from outside the body and against some cancer cells that arise within. 6C/H1*

Some allergic reactions are caused by the body’s immune responses to usually harmless environmental substances. Sometimes the immune system may attack some of the body’s own cells. 6E/H1

Some viral diseases, such as AIDS, destroy critical cells of the immune system, leaving the body unable to deal with multiple infection agents and cancerous cells. 6E/H4

Vaccines induce the body to build immunity to a disease without actually causing the disease itself. 6E/M7** (BSL)

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