Immune system review

- B cells are lymphocytes

- they play a large role in the immune response

- the functions of B cells are:

• to make antibodies against antigens
• perform the role of antigen-presenting cells (APCs)
• and develop into memory B cells after activation by antigen interaction
• they kill pathogens
  

- B cells are an essential component of the adaptive immune system

- B cells circulate in the blood and lymphatic system

-  formed from activated B and T cells that are specific to the antigen encountered during the primary immune response.

- These cells are able to live for a long time, and can respond quickly following a second exposure to the same antigen.

- if a person has an infection, his/her memory cells remember how to get rid of the virus that causes the disease

- once the virus has been fought off once any future infections will unlikley result in a person becoming ill.

- B effector cells are made when the B cell is stimulated

- the B cell differentiates into B effector cells

- The B effector cells can the differentiate into plasma cells.

- these plasma cells then secrete antibodies.

- these antibodies then bind to antigens identifying them for easier destruction.

T helper cells:

When activated these stimulate the B cells

- the B cells then divide and become capable of producing antibodies

- they also enhances the activity of pathogens

active T killer cells:

- these destroy cells with antigens on their surface that are recognised as non self

- this includes body cells infected with pathogens

- unfortunately it also includes tissues recieved as a transplant from another person.

- macrophages and neutrophils are a type of phagocyte

- phagocytes are white blood cells that engulf bacteria and other foreign matter in the blood and tissues.

- a bacterium with antigens on its surface is engulfed by a macrophage

- is is then enclosed in a vacuole

- lysosomes fuse with the vacuole releasing enzymes that destroy the foreign material.

- neutrophils leave blood capillaries by squeezing between the cells of capillary walls

- they ingest and destory bacteria

- natural killer cells are a type of lymphocyte

- they are found in the blood and lymph

- unlike B and T cells they do not use specific antigen recognition

- instead they provide immunity against cells invaded by viruses and cancerous cells