Infectious Diseases Part I: The Immune System Flashcards
(22 cards)
What is the immune system?
The immune system is a host defence system comprising many cells and processes to protect the body against diseases.
What are the functions of the immune system?
- Detect a wide variety of pathogens that cause diseases.
- Distinguish pathogens from body’s own healthy cells.
- Destroy and remove pathogens.
What are the types of immune system?
- Innate immune system
- Adaptive immune system
Name the cells involved in the innate immune system.
- Neutrophils
- Basophils / Mast cells
- Eosinophils
- Monocytes / Macrophages
- Dendritic cells
- Natural killer cells
How many gene clusters code for light chains of antibodies?
2.
Which chromosome numbers are the gene clusters that code for light chains in antibodies found in?
Chromosomes 2 and 22.
What does each light chain gene cluster have?
- Series of variable (V) genes
- Series of joining (J) genes
- One or more constant (C) genes
How many gene clusters code for heavy chains of antibodies?
1.
Which chromosome numbers are the gene clusters that code for heavy chains in antibodies found in?
Chromosome 14.
What does each heavy chain gene cluster have?
- Series of variable (V) genes
- Series of diversity (D) genes
- Series of joining (J) genes
- Series of constant (C) genes
How many gene clusters are expressed in an individual B cell?
1.
Recall that the 2 light chains in an antibody are identical!
How do light chain gene clusters undergo rearrangement of genes?
Via somatic recombination:
* 1 of V gene recombines with 1 J gene to create VJ pair, catalysed by recombinase
* Transcription begins at L exon, finishes at C segment.
* Light chain pre-mRNA is spliced, joining VJ segment to C exon, forming mature mRNA
* Translation of mature mRNA occurs at rough ER.
How do heavy chain gene clusters undergo rearrangement of genes?
Via somatic recombination:
* 1 D gene joins to J gene to form random combination of DJ pair.
* 1 V gene joins to rearranged DJ gene segment to form VDJ gene segment.
* pre-mRNA undergoes transcription.
* Splicing occurs to join VDJ gene segment to C exons, forming mature mRNA.
* Translation occurs to form polypeptide.
What are the different classes of antibodies?
- IgM
- IgG
- IgA
- IgE
- IgD
What classes of antibodies do naïve B cells express as B cell receptors?
IgM and IgD.
Where does class switching occur?
It occurs in the nucleus of the B cells.
What is class switching?
It involves change of amino acid sequence in the constant region of the heavy chain.
How can B cells benefit from class switching?
It allows for more efficient humoral response.
How does class switching occur?
Class switching occurs in individual B cells by further excision of DNA in the heavy chain gene cluster, resulting in the same VDJ segment to lie next to a different C gene, retaining the same epitope specificity in the antibody but with a different constant region.
What is class switching dependent on?
It is dependent on the cytokines released by helper T cells that trigger class switching.
What catalyses somatic hyper-mutation?
Cytidine deaminase.
How do B cells benefit from somatic hyper-mutation?
The mutations may increase binding affinity of the antibody for its epitope.
