TOPIC 6 - IMMUNOLOGY

Question 1

Lymphocytes are defined by

Answer 1

the antigen receptor they express on the surface of the cell.

Question 2

The clonal selection theory

Answer 2

that each lymphocyte bears a single type of antigen receptor with a unique specificity. These are generated during development PRIOR to exposure to the antigen.

Question 3

B cell receptor chains

Answer 3

2 heavy chains and 2 light chains.

Question 4

T cell receptor chains

Answer 4

1 alpha (homologous to heavy chain) and 1 beta (homologous to light) chain.

Question 5

B cells recognise

Answer 5

3D form of pathogen

Question 6

T cells recognise

Answer 6

antigen in the form of peptides in the groove of MHC

Question 7

CD4 T
CD8 T
MHCs

Answer 7

4= II
8 = I

Question 8

What does a co receptor do

Answer 8

Co receptors from the T cell help to bring the MHC closer to the T cell (CD8 and CD4 are termed co receptors)

Question 9

Each chain of a receptor is coded for by…

Answer 9

its own gene

Question 10

Regions of high variation in protein structure of receptors are termed:

Answer 10

hypervariable regions and determine specificity of receptor

Question 11

CDR3

Answer 11

is the most variable due to being the join between multiple segments

Question 12

Heavy chain has

Answer 12

V D J segments

Question 13

Light chain has

Answer 13

V J segments

Question 14

Somatic recombination mechanism

Answer 14

RAG 1 and 2 each recognise an RSS (one 12 and one 23).

1 curves around so that complexes joined side on.

Cleavage of DNA occurs creating hairpin at end of each segment

hairpins cleaved, DNA ligase joins segments together

Question 15

Nucleotide deletion and addition at junctions

Answer 15

Terminal deoxynucleotidyl transferase (TDT) can add nucleotides

Exonuclease removes nucleotides

Create imprecise ends in CDR3 region.

Known as junctional diversity

Question 16

Isotype switching

Answer 16

T follicular helper cell sees virus in groove, notices same virus in B cell, provides help by sending cytokine signal to trigger switching

forms a loop between variable part and desired isotype gene, cuts off loop so desired isotope is transcribed

not RAG 1 and 2

Question 17

3 changes that occur in tumourogenesis

Answer 17

immortalisation: failure to die, divide indefinitely, sensitive to constraints of growth
transformation: failure to observe normal constraints of growth (no longer sensitive to contact inhibition, start growing on each other)
metastasis: ability to invade normal tissues

Question 18

What is a (Proto)-Oncogene

Answer 18

a normal gene which when mutated can cause transformation.

Question 19

Explain burkitts lymphoma translocation

Answer 19

c-myc oncogene inserted into region where expression is driven by Ig heavy chain regulatory sequences.

Gene loses own regulation and starts proliferating

either T or B cells

Question 20

transgenesis

Answer 20

addition of function

introduce new gene into genome

Question 21

knockout

Answer 21

removal of function

remove gene from genome

Question 22

what is a promoter

Answer 22

a regulatory sequence that will determine where and when the transgene is active

Question 23

what is a transgene

Answer 23

the gene being inserted into the genome

Question 24

what is a targeting construct

Answer 24

a targeting construct is a vector that contains part of the flanking DNA in the genome, that can be added to the cell to replace the gene strand and cause a knockout

Question 25

what is a selection marker

Answer 25

something that will code for a trait that allows you to select against instances where the gene inserted in the wrong place and select the genes inserted in the right place

Question 26

Outline CRISPER-cas

Answer 26

2 compulsory components: Cas9 a nuclease which cleaves DNA gRNA which contains homologous sequences that target the gene of interest gRNA binds to target gene, cas9 cuts gene, repair by the cell could result in error resulting in a knockout template DNA can also be added which can be used to repair the cut and give precise mutations

Question 27

what is a parasite

Answer 27

An organism which lives/feeds off another organism (host) without providing any benefit to that host

Question 28

outline trypanosome structure and life cycle

Answer 28

unicellular fly and mammalian host in bloodstream variant surface glycoprotein covers surface, is the antigenic target. invariant SG is hidden by VSG. VSG switching by using different VSG genes helps avoid antibody recognition, antigenic diversity

Question 29

3 mechanisms of VSG switching

Answer 29

Gene conversion: replacement of the expressed VSG gene by a pre-existing silent copy. Most important mechanism as it allows the parasite to use the silent subtelomeric VSG genes. Telomere exchange: homologous recombination between telomeres. In situ switch: activating another VSG expression site. Mechanism not well understood.

Question 30

Outline malaria

Answer 30

caused by plasmodium P. falciparum mostly infects humans can have natural acquired immunity but slow, fast anti disease immunity, slow anti parasite immunity

Question 31

CD8 T cells could NOT kill red blood cells because

Answer 31

they do not express MHC class 1 as it is only expressed in nucleated cells.

Question 32

How does infection avoid splenic clearance

Answer 32

PfEMP1 protein expressed on surface allows sequestration of red blood cell to vessel wall. Avoids antibodies by newly infected red blood cells change the var gene used to encode PfEMP1. Antigenic diversity allows avoidance of antibodies.