The Immune System

Question 1

What are examples of bacterial pathogens?

Answer 1

Enterobacteria, salmonella enterditis, campylobacter jejuni, escherichia coli, and helicobacter pylori.

Question 2

What are the 2 types of bacterial pathogen?

Answer 2

Intracellular pathogens such as mycobacteruym tuberculosis, and arthropod transmitted pathogens such as borrelia burgdorferi.

Question 3

What are viruses?

Answer 3

Acellular (noncellular) pathogens that are composed of nucleic acid and a few proteins and they do not metabolise. They can only reproduce in systems that can perform these functions - living cells. They use the cells synthetic machinery and usually destroy the host cell in the process.

Question 4

What are viroids?

Answer 4

The simplest infective virus which is made up of only genetic materials.

Question 5

What are virions?

Answer 5

The individual viral particles outside a host cell.

Question 6

What is the virion genetic material?

Answer 6

Either DNA or RNA and it is generally surrounded by a capsid or protein coat.

Question 7

What does the protein coat of a virion determine?

Answer 7

The characteristic shape of the virion.

Question 8

Why are viruses unaffected by antibiotics?

Answer 8

They lack the cell wall structure and ribosomal biochemistry of bacteria.

Question 9

What are arboviruses?

Answer 9

Viruses that infect both insects and vertebrates. The virus passes from arthropod to vertebrate through an insect bite. The arthropod is the vector/carrier.

Question 10

What are prions?

Answer 10

Protein-only infectious agent.

Question 11

What are protists?

Answer 11

Eukaryotic pathogens which do not fit into the 3 familiar kingdoms (plantar, Animalia, fungi).

Question 12

What are diplomonads and parabasalids, and what is an example of each?

Answer 12

Pathogens that represent the earliest surviving branches in todays tree of eukaryotic life. Giardia Lamblia is a parasitic diplomonad that contaminated water and causes giardiasis. Trichomonas vaginalis is a parabasilid responsible for an STD.

Question 13

What are euglenozoans?

Answer 13

Kinetoplastids are unicellular parasitic flagellates with one large mitochondrion that contains a kinetoplast which houses multiple DNA molecules and proteins. Trypanosomes are human pathogens that cause sleeping sickness and Chagas disease.

Question 14

What are alveolate/apicomplexans?

Answer 14

Exclusively parasitic. The apical complex is a mass of organelles contained in the apical end of their spores which help the apicomplexan invade its host tissue. Apicomplexans of the genus Plasmodium are the cause of Malaria. The parasite is an extracellular parasite in the mosquito and an intracellular parasite in the human host.

Question 15

What are the 2 main types of WBC’s?

Answer 15

Phagocytes and Lymphocytes (B and T cells).

Question 16

What is the function of RBC’s (erythrocytes)?

Answer 16

Transport oxygen and carbon dioxide.

Question 17

What is the function of platelets (cell fragments without nuclei)?

Answer 17

Initiate blood clotting.

Question 18

What is the function of basophils (phagocyte)?

Answer 18

Release histamine and may promote the development of T cells.

Question 19

What is the function of eosinophils (phagocyte)?

Answer 19

Kill antibody-coated parasites such as worms.

Question 20

What is the function of neutrophils (phagocyte)?

Answer 20

Phagocytose antibody-coated pathogens.

Question 21

What is the function of mast cells (phagocyte)?

Answer 21

Release histamine.

Question 22

What is the function of macrophages (phagocyte), and what immune cell are they developed from?

Answer 22

Developed from monocytes and engulf and digest microorganisms. Also activate T cells. Can also produce cytokines which may signal the brain to produce a fever during an inflammatory response.

Question 23

What is the function dendritic cells (phagocyte)?

Answer 23

Present antigens to T cells. Also have highly folded plasma membranes that can capture invading pathogens.

Question 24

What is the function of B cells (lymphocyte)?

Answer 24

Differentiate to form antibody-producing cells called plasma cells/effector B cells, and memory cells.

Question 25

What is the function of T cells (lymphocyte)?

Answer 25

Kill virus-infected cells and regulate other WBC’s.

Question 26

What is the function of natural killer cells (lymphocyte)?

Answer 26

Attack and lyse virus-infected or cancerous cells.

Question 27

What are the 4 groups of protein that play key roles in defending against disease?

Answer 27

Antibodies, T cell receptors, major histocompatibility complex (MHC) and cytokines.

Question 28

What are some physical barriers of the nonspecific (innate) defence system?

Answer 28

• Skin
• Bacteria and fungi on surface of skin which compete with pathogens for space/nutrients.
• Tears, mucus, saliva contain the enzyme lysozyme.
• Mucus and cilia in respiratory tract.
• HCL and proteases in stomach.
• Bile salts in small intestine.

Question 29

What are the 3 defences of antimicrobial complement proteins in vertebrate blood?

Answer 29

• Attach to microbes, helping phagocytes recognise and destroy them.
• Activate inflammation response, attracting phagocytes to the site.
• Lyse invading cells.

Question 30

What are interferons and what do they do?

Answer 30

Proteins released by animal cells that increase resistance to viral infection.

Question 31

What do basophils do?

Answer 31

Release histamine.

Question 32

What does histamine do?

Answer 32

Causes capillaries to become leaky allowing plasma and phagocytes to escape into the tissue.

Question 33

What are the 4 characterstics of the adaptive (specific) immune system?

Answer 33

1. Specificity - antigens are specifically recognised by T-cell receptors and antibodies.
2. Diversity - The human immune system can distinguish and respond to millions different antigenic determinants.
3. Distinguishing self from non-self.
4. Immunological memory.

Question 34

What are antibodies and how do they work?

Answer 34

Involved in the humoral immune response. Some antibodies are soluble proteins that travel freely in the blood, others are integral membrane proteins on B cells. When a pathogen invades the body, it may be detected by a B cells whose membrane antibody fits one of its potential antigenic determinants.

Question 35

What is the cellular immune response?

Answer 35

Able to detect antigens that are within cells. Destroys virus-infected or mutated cells. Main component consists of T cells.

Question 36

What is the process of clonal selection?

Answer 36

When a B cell binds to an antigen, the B cell divides and differentiates into plasma cells/effector B cells (produce antibodies) and memory cells. The antigen ‘selects’ and activates particular B cells.

Question 37

What do effector T cells do?

Answer 37

Release cytokines.

Question 38

What do memory cells do?

Answer 38

Retain the ability to divide quickly to produce more effector and more memory cells in a secondary immune response.

Question 39

What is artificial immunity/what are the 2 methods?

Answer 39

The introduction of antigenic determinants into the body.

1. Vaccination - Inoculation with whole pathogens that have been modified so they cannot cause disease.
2. Immunisation - Inoculation with antigenic proteins, pathogen fragments or other molecular antigens.

Both initiate a primary immune response to generate memory cells without making the person ill.

Question 40

What causes an autoimmune disease?

Answer 40

When the body is not tolerant of its own molecules and cells.

Question 41

What is cellular division and differentiation of B cells stimulated by?

Answer 41

A signal from the activated helped T cell.

Question 42

What are immunoglobulins and what is their structure?

Answer 42

• Antibody molecules.
• Composed of 1 or more tetramers.
• 2 identical light chains and 2 identical heavy chains.
• Both chains have variable and constant regions.
• Constant regions determine the class of the antibody.
• Variable regions differ in amino acid sequences at the antigen-binding site and are responsible for the diversity of antibody specificity.
• Each tetramer has 2 identical antigen-binding sites making the antibody bivalent.