cells and organs of the immune system

Question 1

What enzymes are unique to neutrophils? Which granules are they in?

Answer 1

myeloperoxidase which catalyzes the formation of hypochlorous acid and singlet O2 (anti-microbial). Primary granules (along with lysozyme and defensins)

Question 2

which cells make up 50-70% of the leukocyte population? what types of infection are they most active in?

Answer 2

neutrophils

acute infections

Question 3

What is the difference in basophil action during primary and secondary exposure to allergens?

Answer 3

Primary exposure to allergens causes production of IgE molecules–> some IgE binds to allergens and some binds to receptors present on surface of basophils

upon Secondary exposure, IgE is already present on surface of basophils so when receptor on basophil (IgE) binds to allergen it leads to a signalling–> degranulation–>release of histimine–>allergic reactions

Question 4

which cells have granules that contain histamines?

Answer 4

basophils

Question 5

What are the different pathways that monocytes can kill ingested microbes? (4)

Answer 5

1. generation of reactive oxygen intermediates
2. reactive nitrogen intermediates, antimicrobial peptides
3. by fusion of phagosomes containing bacteria with lysosomes
4. Antimicrobial peptides

Question 6

In what compartment do DC’s process extracellular protein antigens? Which MHC class are they associated with?

Answer 6

Extracellular proteins antigens are phagocytosed by DCs and then processed in the endosomal compartment, where it breaks down the antigen and is associated with MHC class II molecules before the whole complex is moved to the surface for CD4+ cell recognition

Question 7

In which compartment are Viral protein antigens processed in DC’s? Which MHC class are they associated with?

Answer 7

Viral proteins from intracellular virus are processed in the proteosomes of DC’s. the processed antigen is transported by TAP to the rough ER where it is associated with MHC class I molecules and then the complex is moved to the surface for recognition by CD8+ T cells

Question 8

Which cells secrete perforin and granulysin to kill the target cell?

Answer 8

Natural killer cells (non-specific)

CD8+ T cells ( when recognize antigen in association with MHC class I)

Question 9

CD4+ T cells recognize protein antigens that are displayed on DC surfaces in association with which MHC class?

Answer 9

MHC class II

Question 10

CD8+ T cells recognize protein antigens that are displayed on DC surfaces in association with which MHC class?

Answer 10

MHC class I

Question 11

What stimulates natural killer cell action?

Answer 11

recognition of cells that express low levels of MHC class I molecules

Question 12

What are the two classes of CD4+ T cells and what do they each secrete?

Answer 12

T helper 1 cells secrete IL-2 and IFN-gamma –> activate macrophages and neutrophils to fight infection

T helper 2 cells secrete IL-4, IL-5, and IL-10 –> stimulate B cells to produce antibodies

Question 13

What is a plasma cell? What is its function? What antigens does it express?

Answer 13

When B cells encounter antigens, they multiply and form plasma cells. Plasma cells live for 30 days and produce antibodies. they do not express any B cell receptors on their surface.

Question 14

What do B cells produce in response to T- cell independent antigens? What is an example of a T cell independent antigen?

Answer 14

LPS

B cells produce IgM antibodies

Question 15

What do B cells produce in response to T-cell dependent (protein) antigens? What is this called?

Answer 15

all antibodies
IgG, IgM, IgE, and IgA

this is called class switching

Question 16

What are primary lymphoid organs?

Answer 16

thymus and bone marrow

Question 17

What are the major selective processes in T cell production and where do they occur?

Answer 17

in the thymus cortex, prothymocytes acquire CD3, CD4 and CD 8 antigens (double + cells)

then the cells undergo positive selection, where the cells that cannot recognize MHC class I and MHC class II molecules are destroyed.

surviving cells then lose one of their antigens and become single + cells (either expressing CD 4 or CD8)

in the medulla of the thymus, these remaining cells undergo negative selection where they are eliminated by apoptosis if they react to self-antigens.

all remaining T cells leave the thymus

Question 18

What are secondary lymphoid organs and what takes place there?

Answer 18

spleen, lymph nodes, tonsils and payers patches

secondary lymphoid organs trap microbial antigens and provide antigenic exposure to T and B cells.

Question 19

In addition to the MHC class I or II recognition on DC's (signal 1), which additional binding must occur in order for T cell recognition to take place and to initiate a response?  
Where are the additional markers (co-stimulators) acquired?

Answer 19

Signal 2

• CD 80 and CD86 on surfaces of DC’s bind to CD 28 on T cells
• ICAM (intracellular adhesion molecule 1) on DC’s binds to LFA (leukocyte function associated antigen) on the surface of T cells.

additional markers (ex. CD28 and LFA) are acquired in secondary lymphoid organs