The immune response, antibodies and WBC count (Chapter 11) Flashcards Preview

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Define immunity

The protection against disease provided by the body's internal defence/immune system


What 3 things constitute the external defence system?

Skin, HCl in stomach, blood clotting


What is an antigen?

A substance foreign to the body which stimulates an immune response


Which cells recognise antigens?



What are examples of antigens?

Glycoproteins on the surface of pathogens or their waste material


What is an antibody?

A glycoprotein (immunoglobulin) made by plasma cells derived from B-lymphocytes, secreted in response to an antigen


What is the immune response?

The complex series of responses of the body to the entry of a foreign antigen, involving the activity of lymphocytes and phagocytes


Define self substances

Substances produced by the body that the immune system does not recognise as foreign ∴ they do not stimulate an immune response


Define non-self substances

Any substance/cell that is recognised by the immune system as being foreign and will stimulate an immune response


Where do the cells of the immune system originate from?

The bone marrow


What are the two groups of WBCs?

Phagocytes and lymphocytes


What are the two groups of phagocytes?

Neutrophils and macrophages


Describe the characteristics of phagocytes

- They are produced throughout life in the bone marrow and are stored there before being distributed around the body in the blood
- They remove any dead cells and invasive microorganisms


Describe the characteristics of neutrophils

- Smaller than macrophages
- Short-lived cells


Describe the characteristics of macrophages

- Larger than neutrophils
- Found in organs rather than blood e.g. liver/kidney
- After they are made in the bone marrow, they travel in the blood as monocytes, which develop into macrophages in the organs
- They are long-lived cells


What is the role of macrophages in the immune response?

They do not destroy pathogens completely but cut them up to display antigens that be recognised by lymphocytes


Describe the role of neutrophils in the immune response (5 stages)

1) Neutrophils move towards the pathogens, attracted by chemicals released e.g. histamine by the cells under attack and the pathogens, which may be clustered together and covered in antibodies
2) The ABs further stimulate the neutrophils to attack the pathogens bc the neutrophils have receptor proteins on their surfaces that recognise AB molecules and attach to them
3) When the neutrophil attaches to the pathogen, the neutrophil's CSM engulfs the pathogen and traps it within a phagocytic vacuole (endocytosis/phagocytosis)
4) Lysosomes and the phagocytic vacuole fuse
5) Digestive enzymes are secreted into the phagocytic vacuole ∴ destroying the pathogen


What happens after the neutrophils kill and digest some pathogens?

The neutrophils die and often collect at the site of infection to form pus


Describe the characteristics of lymphocytes

- Smaller than phagocytes
- They have a large nucleus that fills most of the cell


What are the two types of lymphocytes?

B and T cells


Where and when are lymphocytes produced

In the bone marrow before birth


What type of lymphocytes can carry out immune responses?

Mature lymphocytes


How are B and T cells specialised and what does this mean?

Each type of mature B and T cell is specialised to respond to one antigen ∴ they can overall respond to any type of antigen


What happens as B cells mature?

- B cells remain in the bone marrow until they are mature and then spread throughout the body, concentrating in lymph nodes and the spleen
- As each B cell matures, il gains the ability to make just one type of AB molecule - the genes that code for ABs are changed in a variety of ways to code for diff ABs
- Each cell then divides to give a small no. of clones that can all make the same type of AB


What happens to ABs before an immune response?

They remain in the CSM - part of each AB forms a glycoprotein receptor, which can combine specifically with one type of antigen


Describe the response of a B cell to an antigen

1) Clonal selection - when the antigen enters the body for the first time, the B cells with receptors complementary to the antigen are stimulated to divide by mitosis
2) Clonal expansion - the small clone of cells divide repeatedly by mitosis so that a huge number of identical B cells are produced over a few weeks
3) Some of the activated B cells become plasma cells that produce AB molecules v quickly and secrete them into diff parts of the body e.g. blood and lymph
4) Other B cells become memory cells which remain circulating in the body for a long time


How long do plasma cells live?

Not very long (several weeks) but the AB molecules that they have secreted stay in the blood for longer, but eventually decrease in concentration too


Why is the primary response to the antigen slow?

- At this start of the response, there are v few B cells that are specific to the antigen and it take time for them to be selected and cloned
- It also takes time for the T helper cells to become activated


Why is the secondary response to the antigen much faster?

- There are now many memory cells which divide rapidly and differentiate/develop into plasma cells and more memory cells
- ∴ many more ABs are produced and the pathogens can be destroyed and removed before any symptoms develop
- clonal selection and expansion happens much faster


How come some viral infections can infect repeatedly when we have memory cells?

There are many different and new strains of the viruses e.g. cold and flu each with different antigens ∴ there is only and always a primary response, during which time we often become ill

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