Immunityis the ability to protect your body from outside organisms that can cause diseases, pathogens.
When a pathogen attacks your body, the immediate response our body makes is to counter-attack the pathogens with our white blood cells.
antibodies.PNGThe picture above shows how phagocytosis works. This is the process where white blood cells engulf the foreign matter in order to destroy it.

What is a pathogen: A pathogen is something which produces diseases or refers to an infectious organism. It is a microbe (for example, bacteria and viruses).

Immunity vocabulary – defined ("Pathology):
Active Immunity: When an individual is exposed to an antigen and in response to that, their body becomes immune.
Passive Immunity: When an individual becomes immune and that immunity is transferred to a non - immune individual.
Natural Immunity: When an individual is exposed to an antigen naturally as it is part of everyday life.
Artificial Immunity: When an individual is exposed to an antigen that is deliberately introduced to the body, by vaccines are example.


Types of Immunity ("Pathology):
Active Natural Immunity: When an individual is exposed to a harmful antigen, catches the disease and recovers from in. In result, their body becomes immune and he or she will never catch that disease again.
Active Artificial Immunity: When an individual is exposed to an antigen that is deliberately introduced into his or her system by a vaccine.
Passive Natural Immunity: When antibodies are transferred from one individual to another. This normally only occurs between the mother and child right after post – delivery. The antibodies can give the child protection, however these antibodies will deteriorate and sooner or later the child has to rely on his or her own immune system. Antibodies can also be transferred from mother to child through breast milk.
Passive Artificial Immunity: When antibodies are deliberately transferred from one individual to another by the method of injection. This type of immunity takes immediate effect, however this does not last long.

Primary and Secondary Immune Responses:

When an individual encounters a virus or bacteria for the first time, his or her immune system gives a primary respond. When this occurs, the T – Cells and B – Cells meet the antigen, thus are activated and multiplies itself into 2 cells: Memory B cells and Plasma cells. The Plasma cells are the main cause of the primary response while the Memory B cells are there to remember the disease. Following this, the levels of the antibodies increase rapidly, however then begins to decrease as the Plasma cells start to die off.

As the primary response disappears a second injection of the antigen is injected into the individual and this triggers the secondary response. When this occurs, more cells participate in this response as the system is familiar with the disease. Therefore, much more antibodies are produced in the secondary response than the primary response ("Primary)

Lymphocyte and Phagocyte (Difference between Phagocyte) :
A lymphocyte is a small white blood cell, whose purpose is to fight infections and immune responses to the body.
A phagocyte can be thought of as a pac - man. Its purpose is to eat and consume any waste material.

A phagocyte eating a yeast cell:

external image 15-11_Phagocyte_1.jpg
"The Innate Immune Response." Bakersfieldcollege. N.p., n.d. Web. 25 May 2011.

A pac - man eating pac dots:
external image pacman.jpeg

"Pac-man's Past." Animeradius. N.p., n.d. Web. 25 May 2011.

Our immune system

Our body creates a defense system to the response to infection by a germ. There are two main stages of this defense: the innate immune response and the adaptive immune response. The first is a general immune response and the adaptive immune response is a more specific targeted attack on the germ.
Adaptive immune response

Adaptive immune response refers to the response that happens that has had enough time to recognize the germ causing the infection and can target it’s action specifically to that particular type of germ. An action that is targeted is more efficient and effective than the general innate response above. There are two different types of adaptive immunity:

- Cellular immunity: White blood cells are made to specifically target the invading germs

- Humoral immunity: This is when the system specified a special substance in the surface of invading germs which is antigens. As we already know, it then produces its own chemicals known as antibodies to specifically target the antigens and inactivate them. Antibodies marked the germs for destruction by white blood cells.

Same same but different?

B-lymphocyte and a T-lymphocyte (Difference between T - lymphocyte):

T – Cells are used to identify antigens and to release chemicals that can destroy the antigens.

B – cells are used in the production of antibodies. When it encounters an antigen it will divide into two types of cells: plasma cells and memory B cells. The memory cells remembers the type of antigen in the immune system while the plasma cells will fight to get rid of the antigens.


Vaccination is how we trick our body to accelerate the immune system.

We do this by injecting a weak or dead pathogen into our body so that as an immediate response, our body creates an antibody for it without our body being even harmed by the pathogen since it is weaken or dead already.

This prepares us to make antibodies faster if the same type of pathogen happens to attack our body again. This process still takes few days, from 3 up to 10 days, as our body needs time to figure out how to make the right antibody for this pathogen.

For an immediate protection from the pathogen, we can also inject another person’s antibodies to that type of pathogen so that our body doesn’t need few days before figuring out which type of antibody has to be made. This gives us immediate protection against the pathogen but it does not last long as our body will begin to attack the foreign antibodies as they come from outside the our own body.



How does a single infection by a pathogen can provide lifelong protection against a disease:
Vaccines give the body a preview of the bacteria or virus. This prepares the body in advance against deadly diseases and teaches the body how to defend itself. If the body encounters the bacteria again, the body will be prepared.
When a weakened or dead antigen is introduced to the body through a vaccine, the B – cells go to work and fight the disease causing pathogens by creating antibodies. The antibodies will act on the antigens and destroys the pathogens, thus when an individual receives a vaccine he or she is usually free from that specific type of pathogen for his or her whole life.


Cited Sources:
"Differences between phagocytes and lymphocytes?" Biology Online. N.p., n.d. Web. 25 May 2011. [[http://www.biology-online.org/biology-forum/ about17166.html]].

"Difference between T- lymphocytes and B- lymphocytes?" Answers. N.p., n.d. Web. 25 May 2011. http://wiki.answers.com/Q/ Difference_between_T-_lymphocytes_and_B-_lymphocytes.

How Does the Vaccine Work? . CancerCouncilVic. Youtube. Web. 30 May 2011. http://www.youtube.com/watch?v=jq346hkaEec&feature=player_embedded.

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Pham, Trung and Jae Hyun, Park. “Immunity and Vaccination.” Wikispace. N.p., n.d. Web. 1 June 2011.