immunology

Question 1

Describe antigen

Answer 1

An antigen is a molecule (protein/glycoprotein/glycolipid ect) that stimulates an immune response that results in the production of a specific antibody from a specific plasma cell.

Note: (antigen = Antibody generator)

Question 2

Describe antibody

Answer 2

An antibody is a protein specific to one antigen
Produced by a specific plasma cell
+ draw it out - Y shapes molecule with disulphide bonds - antigen binding site - variable and constant regions

Question 3

List 4 types of cells that will elicit an immune response (due to the antigens they display)

Answer 3

Cells infected by a virus
Cells from another organism/transplant
Cancerous cells
Bacteria Cells

Question 4

Describe phagocytosis

Answer 4

1. Engulf pathogen by endocytosis
   2.Forming vesicle/phagosomewhichfuses with
   lysosome
   3.lysosomes contain hydrolytic enzymes (lysozymes) that
   hydrolyse molecules of pathogen OR digests pathogen.
   4. antigens are displayed on cell membrane

Note: waste material is also removed by exocytosis

Question 5

Describe how vaccination leads to production of antibodies and immunological memory

Answer 5

1.Vaccine contains antigen from pathogen.
2.phagocyte engulfs and presents antigen on its surface.
3.T helper lymphocyte with complementary receptor protein binds to antigen.
4.T helper lymphocyte releases cytokines to stimulate specific B lymphocyte to divide by mitosis (clonal expansion)
6.clones becomes plasma cells which produce and secrete (monoclonal) antibodies complementary with antigen.
7. Clones become memory B lymphocytes which remain in blood and recognise antigen for a more rapid response and release of more antibodies upon second infection.

Question 6

Contrast passive and active immunity

Answer 6

1.Active involves memory cells whereas passive does not.
2.Active involves production of antibody by plasma cells / memory cells whereas passive antibody is introduced from outside body (eg breast milk/antivenom ect)
3.Active long term, because antibody produced in response to antigen whereas passive is short term, because antibody is broken down.
4.Active takes time to develop as requires formation of memory cells whereas, passive fast acting as antibodies given directly

Question 7

Define the following mutations and describe how they can lead to a non-functional protein (or in this case a different antigen)
-Addition

Answer 7

Addition: an addition of a single base in the DNA base sequence of a gene (frame shift mutation).
Affect:
-changes triplets after mutation (frame shift).

-change in amino acid sequence (primary structure).
-forms ionic / hydrogen / disulfide bonds, between R groups, in different places.
-changes tertiary structure of protein so non-functional (new antigen).

Question 8

State the uses of monoclonal antibodies in medical treatments

Answer 8

Elisa test for presence of foreign antigen (pathogen) or antibody (against pathogen)
Carries drug to a specific cell (eg cancer cell)
Targets and binds to antigens on specific cells (eg cancer)
Block antigens or receptors on cells.

Question 9

Describe the structure of HIV

Answer 9

1.  genetic material is RNA
2.  contained in a capsid
3. containsReverse transcriptase
4.  Phospholipid envelope
5.  has Attachment proteins on lipid envelope

Question 10

Describe the HIV replicates

Answer 10

1. Attachment proteins complementary and bind to proteins on T helper cell.
2. Capsid broken down and releases viral RNA
3. Reverse transcriptase converts viral RNA to cDNA.
4. Viral cDNA incorporated into host DNA (NOW INFECTED).
5. Transcription of viral DNA into mRNA
6. Translation of HIV proteins and formation of virions (infectious particle)

Virions bud off the host cell membrane forming their lipid bilayer.

Question 11

Describe the cell mediated response

Answer 11

Specific T helper cell binds to antigen presenting cell and goes through clonal selection.
Release cytokines which:
attract phagocytes
activate cytotoxic killer T cells
activates specifically complementary B lymphocyte
Form memory T cells.

Question 12

Describe the role of the T cytotoxic killer cell

Answer 12

Destroys cancer cells OR cells infected by a virus
By releasing perforin
Creating holes in cell surface membrane of the Antigen presenting cell
Causing cell lysis

Key: destroys one’s own cells.

Question 13

Describe the humoral response

Answer 13

Specific T helper cell bind to specifically complementary B lymphocyte and releases cytokines.
clonal expansion of B lymphocyte.
B lymphocytes differentiate into plasma cells or memory B cells.
Plasma cells produce and secrete specific antibodies complementary to one antigen.
Memory cells involved in secondary response

Question 14

Describe the primary and secondary response

Answer 14

No antibodies due to no exposure to antigen.

Latent period -The time that passes between being exposed to an antigen and having symptoms.
Primary response (1st response to antigen)
clonal expansion of specific B lymphocyte into plasma cells.
Plasma cells produce and secrete antibodies.

Secondary response (2nd exposure to antigen)
Shorter latent period
Memory cells divide into large numbers and create plasma cells.
Produce more antibodies more rapidly.

Question 15

describe the role of antibodies in producing a positive elisa test

Answer 15

(First) antibody binds/attaches /complementary (in shape) to antigen;
washto remove unbound antibodies
(Second) antibody with enzyme attached is added;
(Second) antibody attaches to antigen;
wash to remove unbound antibodies
(Substrate/solution added) and colour changes;