Innate immune system

Question 1

1.1 First line of defence against infections - physical barriers

Answer 1

Skin
- fatty acids in sweat and lactic acid (Ph 3-5 ) in sebaceous glands
stomach acid
- ph (1.5-3.5
Mucous Membranes
- mucous blocks adherence of bacteria and viruses to epithelial cells and trapped pathogens are removed via cillary action, they are move up and either sneezed or coughed out.
Bodily fluids (tears,saliva and urine)
- contains bactericidal components like lysozyme, proteolytic enzyme, spermine

Question 2

1.2 If pathogens miss the first line of defence

Answer 2

Then there is 3 next line of defence which include(all in book)
- phagocytosis
- pattern recognition receptors (
-complement system

Question 3

3 different pathways that activate complement cascade

Answer 3

classical pathway :
- triggered by antigen-antibody complex binding to c1,c2 and c4
alternative pathway :
- C3b trigger C3 convertase which activates c3. activated by viruses, bacteria and fungi
mannose lectin binding pathway:
-mannose residues on pathogen surface activate C4 and C2 to form C3 convertase

all pathways lead to activation of C3 which lead to activation of c3a (promotes inflammation) c3b ( an opsonin)

Question 4

membrane attack complex (part of complement system )

Answer 4

complements that inserts them selves into the surface of microbes forming a cytotoxic pore leading to cell lysis.
- include in order: C5b, c6, c7,c8 and c9

Question 5

Dendritic cells

Answer 5

antigen presentation is largely carried out by the DC’s, they migrate to the tissues an sample their environment. they are equipped with TLR’s and other PRRS. when activated, they migrate to the lymph nodes where they perform antigen presentation awakening the cells of the AIS

Question 6

Major histocompatibility complex( MHC 1)

Answer 6

• are present in most nucleated cells of the body, if abnormal peptides are presented to the t cells via MHC 1 it indicates an intracellular infection or abnormal cell. contains the unique proteins HLA - A, HLA - B, HLA - C . THE REsponse is to kill the cell.

Question 7

Major histocompatibility complex ( MHC 11)

Answer 7

present in professional antigen presenting cells(dendritic and macrophages ). if abnormal peptides are presented to t cells via MHC 11 it indicates an infection external to the cell. killing the cell will not eradicate the problem. contains unique proteins HLA-DQ, HLA - DP, HLA - DR

Question 8

INtracellular infections NATURAL KILLER CELLS

Answer 8

infections that occur in a cell are protected from complements and phagocytosis. Therefore Natural killer cells will kill the infection . NK cells express TLR’s and are activated in the presence of PAMP’s and interferon-a and interferon - b . they survey cells for abnormal patterns of proteins on the surface. for example if MHC is missing or if DNA has been interrupted.

Question 9

Type I Interferons (IFN-α and IFN-β)

Answer 9

• Anti-viral (and anti-bacterial) interferons, produced after PAMPs activate TLR receptors via the interferon-regulated factor (IRF) family of transcription factors.
• Antiviral effects are mediated by reduced protein translation, degradation of viral and host mRNA and reduction of expression of the MHC.