L4

Question 1

Explaing the stages of immune respons ?

Answer 1

1 contact with antegen
2 inducation of information
3 antigen processing by APC ( antegin is broken down by enzymes insiede tge antegin presenting cell
4 antigen recognition by lympicytes
5 activation of effector mechanisms
6 destruction if antigens and excration of products of destruction

Question 2

Explain the anigen presentation

Answer 2

1- its all beging with the invasion of forgein organisim to the body these ingested by antigen presbting cells they are 3 type but the majorty of them include debdrite cells , microphages , B-cells 
2- once forgein organisms are phagocyted , they form an Endosome , which is fuses with lysosomes that contain enzymes to kill ans digest the organisms 
3- the CD8 molecule binds to MHC1 helps to gnerate an intercellular signal of TCR engegment 
4 endogenous processinf of intercellular phatgpns thus leads to actviations of cytotoxic effector cells able to destroy infected cell 
5 the exogenous pathway is for the MHC class 2 meloucles and is used by the antigen presnting cell 
6 in the rough endoplasmic reculum the native MHC class 2 associy with each other and 3rd protein called invariant cahin which stabliazed the complex 
7 the resulting MHC 2 peptied complex trabsported  to cell to be seen bt the TCR of CD4 T-helper cell

Question 3

Explain the antigen presnting cell Apc

Answer 3

Antigen persnting cells : is cell that display antigen bound by major histocomptability complex (MHC) proteins on its serfuce

Type and functions 
Apc is fall into 2 types professional and non profissinal 
- profissinal antigens persnting cells : that express MHC class 2 moleculs along with co-stimulatory moleucles and TCR and BCR
- non-profissnal : apc express MHC 1 mloucules 
Function and types of non pro :
Non pro antigen presbting cells inclouds all nucleated cell typeij the body , they use MHC class 1 to display endogenous peptieds on the cell membrane .

Type of pro apc :
1- dendritic cells : have the broadest range of antigen presbtation and are necessary for activation of naive T cells
2-macrophages : can be stamulated by T cell secration of interferon after this activation microphages are able to express MHC lass 2
3- B cells : can internalze antigen that bind to their B cell receptor ans presnte it to helper T cells

Question 4

Explain the TCR and BCR recognation receptor

Answer 4

TCR

2 variants of chains antigen recognation site :ab or y8
1 thymus-depndet
t-lymphcytes Tab
2 thymus -independt 
T-lymphocytes  Ty8 

BCR
Membrane -bound ig on the B-cell recptor and its recognat the antigen through the formation if a macromoulecular cluster if definde compastion
T-lymphoctes Ty8

Question 5

Explain the suppression of the immune response

Answer 5

1- when the antigen is removed there is nothing to active
2-termanally defrenteated lymphocytes have a limited life time span and die
3- ig G high concentration through speical receptor the synthisis of antibodeis in a given lymphocytes and its prograssion
4- Reglatory CD4 lymphocytes is the resonsable pf suppresion the immune system
5 NK and NK-like lymphocytes : autokilles they are die by binding the fas recptor on actevated t-lymphocytes
6 neutrophils die by phsiological apoptosis 4-12 hours after leaving the bone marrow
7 macrophages live longer but die after actvite destrctive work

Question 6

Explain the T-cells devolopment , slection , actviation

Answer 6

Devolopmenet : they origneat from hematopatic stem cell which rsied in the bone marrow and some time cloud be in the liver during emberyoinc devolpment , then they go to thymus which there gose to be CD4 or CD8 co receptor

-Selction there is two type of selcetion
Postive and nigative
1-postive : the random genrator produced a large number of thymocytes each of wich have uniqe TCR
Generally T cells usefull if its TCR can be actvatied by our own , here is the usefullness of the positive selction ducking of the TCR to one of the MHC moulcules on thymic epetgelial cells delevards the survaival single T-cell
Positive selction therefore resultss in self-MHC-restraction

2-nigative: among all the thymocytes there is a postive slection for recognaizing our own MHC , some are bound to recognaize some combanation of MHC mulocule persnted it self prefctly
They are auto-reactive and they are dengourns
The seloution is very strong and countenous bnding a sginal indecate the clons of thymocytes under apoptosis

—actviation : the T-cells get actevatied when they are persented with pepteid antigens by MHC class 2 muolcoues which expressed on the surface of the apc

Question 7

Explain the B-cells devolopment , slection , actviation

Answer 7

• Devolopment : B cells devolopment starts in the bone marrow and countenious to the slpeeb and final maturation
• Selction : there are 2 postive and nigative

Postive selcation : when the bone marrow generates the b cells its genrate a lrage number and between the bone marrow and spleen here when the postive slection happens by sending sginal by MHC moulcular and indecate the survaival B cells

-Nogative selcation : some of the b cells cant be recognized and suddnly get selected as postive slecation they are dengours the seloution is very strong and countenos beinding results that indecate defrent signals from the bone marrow to bind the clons

—-activation : b cells actevate when there B cell recptor binds to either sulable of membrane bound antigen