U2) KA5)Mammalian immune response

Question 1

the immune response to parasitic attack in mammals has both __ _____ and ____ aspects

Answer 1

specific

non specific

Question 2

non specific : first line defences

Answer 2

defence : physical barriers - epithelial cells blocks the entry of pathogens / parasites , also kills many microbial parasites. Nasal hairs trap microbial parasite, prevent them from contacting delicate tissue in lungs.

defence : chemical secretions- hydrolytic enzymes in mucus , saliva and tears destroy bacterial cell walls: low ph environments created by the secretions in the stomach , vagina and sweat glands denature the proteins of pathogens. Mucus in the lungs traps microbial parasites. the Mucus is continuously moved away from delicate alveolar tissue by action of cilia

Question 3

second line defence examples

Answer 3

• inflammatory response
• phagocytes
• Natural Killer cells

Question 4

inflammatory response

Answer 4

• some injured/infected cells release signalling molecules including histamine
• causes local blood vessels to dilate and results in increased blood flow to site of injury
• it also brings antimicrobial proteins and stimulates phagocytes to migrate to the area

Question 5

phagocytes

Answer 5

• are white blood cells , which migrate out of blood to tissue fluid which surrounds cells.
• they can engulf the bacteria , viruses and dust particles into a vacuole.

Question 6

natural killer cells

Answer 6

• also a type of white blood cell which can migrate into the tissue fluid. they detect the abnormal cell surface proteins found on virus infected cells and on cancerous cells
• natural killer cells attach to to the stricken cell and release chemicals into it. these cells induce apoptosis
• phagocytes engulf and digest the resulting cell debris

Question 7

How are specific cellular defences triggered- and what does it invokve

Answer 7

• triggered by the antigens on the surface of the parasite
• responses here are specific to the antgien and involves lymphocytes,
• range of white blood cells constantly circulates , monitoring the tissues , if the tissues become damaged or invaded , cells release cytokines that increase blood flow resulting in no specofic and specific white blood cells accumulating at the site of infection or tissue damage

Question 8

What are Lynphocytes

Answer 8

• white blood cells which are found mainly in the lymph glands

Question 9

Lymphocytes present one type of _____ _______ ______ on their _____ . What can these do

Answer 9

• antigen receptor protein on their surface (lymphocytes surfuce )
• these can bind to just one specific antigen

Question 10

Each lymphocyte can only make one type of receptor. why ?

Answer 10

• although each one of us can produce between 1 million and 10 million different antigen receptors each lymphocyte can only make one type of receptor
• this is becuase each lymphocyte is part of a clone - a group of about 1000 identical cells made from a common ancestral cell , which was commited to produce a single type od antigen receptor

Question 11

Tissue fluid is drained from around the bodys cells by the ________ ______

Answer 11

Lymphatic system

Question 12

Where do lymphocytes carry out immune surveillance

- what is this

Answer 12

• the lymph fluid passes through the lymph glands , where the lymohocytes carry out immune surveillance
• this is when they check for specific antigens using the receptor proteins on their surface
• during surveillance,phagocytes in the lymph fluid are also checked for their presented antigen fragments

Question 13

Clonal selection of lymphocytes

Answer 13

• mammal tissue contain many different lymphocytes
• each lymphocyte has an antigen receptor with the capability to recognise a specific parasite antigen.
• binding of antigen to the lymphocytes receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte, with the SAME specific antigen receptor
  Look at diagram on how to pass book page 104

Question 14

What do some selected B lymphocytes do

- how does this help get rid of parasites

Answer 14

• some of these lymphpcytes produce antibodies
• antibodies possess regions where the amino acid sequence varies greatly between different antibodies - this variable region gives the antibody its specificty for binding to the antigen on the parasite
• the antigen antibody conplex formed can inactivate the parasite , making it easier for the phagocytes to find and engulf , or it can cause the parasite cell to undergo lysis

Question 15

Other lymphocytes destory infected cells by inducing _______

Answer 15

Apoptosis
- (although this is a similar function to that of the natural killer cells , these lymphocytes are much more effective but can only attack a cell if it has the specific antigen )

Question 16

What is immunological memory

Answer 16

• once parasite infection has been defeated , some members of the lymohocyte clones are kept as an immunolgical memory
• the long term survuval of a larger population of these memory lymphocyte cells means they produce a quicker and larger response if the specific antigen is detected again

Question 17

• initial antigen exposure produces memory lymphocytes : summarise what this does

Answer 17

These memory lymphocyte cells specific for that antigen ,can produce a secondary response when the same antigens enter the body in the future - they produce a quicker and larger response
- when this occurs, antibody production is enhanced in terms of speed of production , concentration in blood and duration

Question 18

Parasites have evolved ways of evading the immune system.

how ?

Answer 18

• mimicking host antigens -endoparasites mimic host antigens to escape detection and modify the hosts immune response to reduce their chances of destruction
• antigenic variation - allows parasites to change between different antigens during the course of infection of a host, might also allow reinfection of the same host with the new variant.
• integrate genome into host genome- some viruses can escape immune surveillance by integrating their genome into the host genome, existing in cells in an inactive state.