introduction to immune system

Question 1

what are the two types of adaptive immunity, and what types of microbes do these adaptive immune responses combat?

Answer 1

adaptive immunity

1. humoral
   
   1. antibodies neutralize and eradicate extracellular microbes and toxins
2. cell mediated
   
   1. T lymphocytes eradicate intracellular microbes

Question 2

what are the principal classes of lymphocytes, and how do they differ in function?

Answer 2

lymphocytes are the cells of adaptive immunity and are the only cells with clonally distributed receptors specific for different antigens.

two classes

1. B lymphocytes-
   
   1. are only cellsthat produce antibodies.
   2. express membrane antibodies that recovnize antigens
   3. generate plasma cells, secrete antibodies to neutralize and eliminate antigen targets(toxins or invaders)
2. t lymphocytes
   
   1. recognize fragments of protein antigens displayed on other cells.
   2. helper T cells
      
      1. produce cytokines that activate phagocytes,
      2. recruit leukocytes
      3. actvate b cells to secrete antibodies
   3. cytotoxic t cells kill infected cells harboring microbes

Question 3

Two large grouped categories for cells of immunity

Answer 3

1. lymphoid cells-mediators of the adaptive immune system
2. myeloid cells-non-lymphoid cells, play diverse roles including innate immunity

Question 4

what is clonal selection hypothesis

Answer 4

clones of lymphocytes specific for different antigens develop before an encounter with these antigens and each antigen elicits an immune response by selecting and activating the lymphocytes of a specific clone

Question 5

what is immunologic memory?

Answer 5

Only the lymphoid cells(B&T) can generate this response.

1. primary response- initiated by lymphocytes called naive lymphocytes that are seeing antigens for the first time
2. secondary response- more rapid, larger and better able erradicate foreign invader

Question 6

What happens when a naive or memory lymphocyte is activated?

Answer 6

clonal expansion- massive proliferation, generating 1000’s of cells. this is the ramping up of the system.

Question 7

What stop the immune cells from recting against host protein

Answer 7

immunological tolerance-the ability of the immune system to coexist with (tolerate) potentially aantigenic self molecules, cells and tissues

Question 8

give the principal function for cells in these categories

lymphocytes

APC’s

effector cells

Answer 8

Question 9

What are the CD’s and functions of lymphocytes

Answer 9

CD4

1. Helper T cells-help B lymphocytes and phagocytes
2. regulatory t cells-special subset that prevent or limit immune reponses

CD8

1. CTL-kill cells harboring intracellular microbes

Question 10

Where is the orgination maturation site of lymphocytes? What happens after they are matured?

Answer 10

both originate from a stem cell in the bone marrow

B

1. mature in bone marrow

T

1. mature in the thymus

post maturation

1. naive lymphocytes express receptors that look for antigens
2. effetor cells
   
   1. b cells differentiate to plasma cells
   2. T cells differentiate to respected CD(4or8)
3. memory cells are generated

Question 11

The correlation between age and blood T cell concentration

Answer 11

Question 12

What is a common entrance for microbes to the body? Describe the first steps to the adaptive immune system

Answer 12

skin, gastrointestinal, respiratory, and genitourinary tracts- all contain specialized cells located in the epithelium that capture antigens and display them to a T cell and B cells.

these cells are known as antigen presenting cells (APC)

1. dendritic cells(general)
   
   1. activate a naive T lymphocyte by displaying the antigen on its surface.
2. macrophages
   
   1. present antigens to differentiated effector T cells.
   2. may present to B cells
3. B cell
   
   1. may encounter antigen directly
4. follicular dendritic cells
   
   1. resides in the germinal centers of lymphoid follicles in the peripheral lymphoid organs and displays antigens that stimulate the differentiation of B cells in the follicles
   2. DO NOT present antigens to T cells

Question 13

Define key peripheral lymphoid organs and features.

Answer 13

Secondary organs act to assist the lymphocytes circulating the body and bringing antigens in contact with T and B lymphocytes.

1. lymph nodes
   
   1. as lymph pases through the nodes, APCs sample the antigens of microbes.
   2. dendritic cells present processed antigens here(these are refered to as draining lymphnodes)
2. spleen
   
   1. blood entering the spleen flows through a network of channels(sinusoids).
   2. High in {phagocytes] which ingest and destroy microbes and RBC’s
3. MALT-mucous associated lymphoid tissue, where APC’s survey the enviornment
   
   1. tonsils, peyers patches
   2. 1/4 of WBC are in these regions
   3. these cells are able to discriminate commensal bacteria from invaders

Question 14

sketch the anatomy and regions of the lymph node

Answer 14

Follices-

1. Bcells
2. if follicle has responded to T helper cell about antigen, a germinal center will develop as a light staining region.
   
   1. develops highly effective antibodies
   2. also found in spleen
3. contian FDC

paracortex-

1. contains T lymphocytes
2. regular Dendritic cells that present the antigen to the T cells

Question 15

give a general description of the spleen anatomy and regions of cell concentration.

Answer 15

A shows the strucutres worth noting

1. pals =periartriolar lypohoid sheath in combination with follicles, they constitute the white pulp.
2. marginal zone is the indistinct boundary between the red pulp and white pulp

B shows an arteriole with the PALS and a follicle with a prominent germinal center

Question 16

What is a location difference between the effector T and B lymphocytes?

Answer 16

T effector cells must locate the site of infection to locate and attack invader.

B effector cell, plasma cell does not need to migrate, instead its works stationarily pumping out tons of antibodies.

1. plasma cells in the MALT generate antibodies that are secreted in mucosal secretions.

Question 17

Other than the afferent lymph vessel, how can T and B lymphocytes enter the lymph node?

Answer 17

High endothelial venules.

1. effector/memory/naive T cells leave the thymus and naive B cells leave the bone marrow where they follow the chemokine signal to the HEV, where they attach via adhesion molecules.
   
   1. chemokines binds to
      
      1. T=CCR7
         
         1. goes to parafollicular zone and interacts with dendritic cells
      2. B=CXCR5
         
         1. goes to follicles

Question 18

Describe the pathway of naive T and B cells, freshly matured, resonding to the lymph for a new antigen.

Answer 18

1. T leaves the thymus and B leaves marrow and enter lymph node through HEV/lymph. T->parafollicular, B->follicles
2. T->scan dendritic cells->activate->differentiate(CD4&8) respectivly. B->interacts with FDC->undergoes activation.
3. effetor T cell migrates to the infeted tissue and perform function.
4. B differentiate into plasma cells and go to bone marrow or mucosal tissue.
5. Memory cells consist of different population and recirculate or hang out in MALT/epithelial

Question 19

compare and contrast Immunogenicity vs Antigenicity

Answer 19

antigenic molecules are recognized by cell surface receptors: T and B cells, dendritic cells, etc.

immunogenic molecules elicit humoral or cell mediated immune response

all immunogens are antigens, but not all antigens are immunogenic

Question 20

Define the components and the idea of Hapten-carrier response. What does this mean about our immune systems specificity?

Answer 20

hapten=antigen w/o immunogenicity

hapten carrier response=when a hapten is coated with proteins that elicit an immune response, antibodies are generated with respect to the proteins recognized on the surface.

the immune system is incredibly specific against haptens.

Question 21

compare and contrast the primary and secondary lymphoid organs

Answer 21

primary

1. bone marrow
2. thymus

secondary

1. lymph node
   
   1. antigen deposition FROM TISSUE and B/T cell activation, differentiation and proliferation
2. spleen
   
   1. antigen deposition FROM BLOOOOOD and B/T cell activation, differentiation, and proliferation
3. MALT
4. GALT
5. Skin

Question 22

compare and contrast the key differences between innate and adaptive immune responses.

characteristcs: specificity, diversity, memory, reactive to self?
components: physical and chemical barriers,blood proteins, cells

Answer 22

Question 23

identify the five protective mechanisms associated with antigen-antibody binding and explain why they are important to the immune system.

Answer 23

protective mechanism of binding antibodies to antigens

1. agglutination
   
   1. reduces the number of infectious units to be dealt with
2. opsonization
   
   1. coating antigen with antibody enhances phagocytosis
3. neutralization
   
   1. blocks adhesion of bacteria and viruses to the mucosa
   2. blocks attachment of toxins
4. antibody-dependent cell-mediated cytotoxicity
   
   1. antibodies attached to target cell cause destruction by eosinophils and NK cells for a large target like a parasite
5. activation of the complement system
   
   1. causes inflammation and cell lysis

Question 24

How do the innate and immune responses work with respect to ?

1. resonese time
2. specificity
3. response to second exposure
4. components involved

Answer 24

The two systems rely on each other for the protection of the host from invaders. The innate system reacts quickly but can be evaded after several days of battling. in this event the immune system will have used the time generating effector cells to amplify the immune response.

1. normal humans have the concert of having above system in action against an antigen.
2. lacking an innate system will mean a quick death, b/c the immune system takes too long to ramp up
3. lacking an adaptive system means an inevitable death in the long run, b/c the innate system cannot change its specificity like the adaptive can.

Question 25

Explain the difference between primary and secondary immune response.

Question 26

list the characters and draw the associated functions during the process of T cell recognition

Answer 26

Question 27

list the characters and draw the associated functions during the process of B cell recognition

Answer 27

Question 28

draw/explain the difference between humoral and cell-mediated immunity response to an antigen

Answer 28

T

1. APC presents the antigen on surface
   
   1. Th
      
      1. CD4
      2. MHC2
   2. Tc
      
      1. CD8
      2. MHC1

B

1. antigen leads to Ab-secretion