Topic 9 Immune responses Flashcards

1
Q

What typical properties do the innate immunity have?

A

It’s fast and have a non-specific defense and response to injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What comprises the innate immunity?

A

Epithelial barriers (skin, mucous), acidic environment&enzymes, phagocytes, Natural killer (NK) cells, proteins & enzymes that lyse or inactivate bacteria (complement factors)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which cells are the phagocytes?

A

Dendritic cells, macrophages and neutrophils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Whats the role of NK cells?

A

They sense virus infected cells and lyse them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Whats the role of cytokines?

A

They activate macrophages, neutrophils, NK cells and enhance microbial killing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 3 main functions of the complement proteins?

A
  1. C3b bind. to foreign surfaces - induce phagocytosis.
  2. Cleaved C3b into C5a & C3a recruits and activate leukocytes that kill the microbes
  3. Can form the membrane attack complex (MAC)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What’s the classical pathway?

A

Antigen-antibody binding result in C1 binding to constant portion of antibody, cleaving into a and b fragments, followed by formation of C3 convertase and C5 convertase. Ends in formation of the Membrane Attack Complex (MAC) that inserts itself as a pore into foreign cells, causing lysis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What’s the alternative pathway?

A

Starts when C3 spontaneously hydrolyses and C3b binds to a surface (if host cell = rapidly deactivated). Involves factor B and D. Formation of C3 convertase, C5 convertase and resulting in formation of Membrane Attack Complex (MAC)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is the Complement 3 usually found?

A

C3 is usually found in blood plasma/serum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does both the alternative and classical pathway result in?

A

Membrane Attack Complex (MAC) formation that creates a hole in the membrane to kill the cell via osmotic lysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name some links between the inflammatory process and the complement system

A
  • C1 and C3 can be activated by plasmin & Kallikrein or other by-products from coagulation
  • C3-5a can activate leukocytes
  • C5a chemoattractant for neutrophils and macrophages
  • C3b opsonization -> recognition for phagocytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Further explain the opsonization process

A

Bacteria are “opsonized” by the binding of an antibody and C3b to receptors on the phagocyte membrane - which then stimulates phagocytosis. The complex of the antibody and C3b is called opsonin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does the complement react to biomaterials?

A

Surface reaction then through the alternative pathway by C3b binding and through the classical by IgG binding and activating C1. (IgG is the most common AB)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which two enzymes are needed for the complement to create the MAC?

A

First C3 convertase enzymes then C5 convertase enzymes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the complement activation regulated?

A

Short half-life of the enzymes in the cascade. Regulatory proteins called “regulator of complement activation” (RCA) proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can complement activation be controlled at the biomaterial surface?

A
  1. Limit the C3b deposition (reduced amount of nucleophiles at surface)
  2. Immobilize RCA proteins at surface
  3. Induce C5a binding to surface by negative surface groups
17
Q

What typical properties do the adaptive immunity have?

A

Specific defense against individual foreign stimuli. Long-term. Cell-mediated immunity (cytotoxic activity of T cells) and humural immunity (prod. of antibodies by B cells)

18
Q

What is histocompatibility?

A

Each individual expresses many unique HLA proteins on the surface of their cells, which signal to the immune system whether a cell is part of the self or an invading organism.

19
Q

What are MHC/HLA proteins?

A

Major histocompatibility complex in humans are the human leukocyte antigens (HLA)

20
Q

What’s the main function of MHC proteins?

A

The main function of MHC proteins are to bind to antigens derived from pathogens and display them on the cell surface for recognition by the appropriate T-cells.

21
Q

What’s the difference between MHC class I and II?

A

Class I MHC molecules have β2 subunits so can only be recognised by CD8 co-receptors. Class II MHC molecules have β1 and β2 subunits and can be recognised by CD4 co-receptors. In this way MHC molecules decide which type of lymphocytes may bind to the given antigen with high affinity, since different lymphocytes express different T-Cell Receptor (TCR) co-receptors.

Class II: “come and do something!” to T helper cells
Class I: “come and kill me!” to T cytotoxic cells

22
Q

What’s cluster of differentiation (CD)?

A

surface molecules used for immunophenotyping cells as they have different CD proteins expressed at different stages of maturation or differentiation. E.g. helper T cells are CD4 positive. These CD often act as receptors.

23
Q

Briefly describe the stages of cell-mediated immunity

A

A T helper binds to the APC presenting the antigen. It can then activate cytotoxic T cells that kill cells displaying the antigen. The helper and cytotoxic T cells also clone themselves into memory cells. They also activates B cells that also clone into memory cell and also differentiate into plasma cell secreting antibodies.

24
Q

What’s the role of APCs?

A

APCs, or antigen presenting cells, endocytose foreign material/bacteria/viruses, then move to the lymph nodes where the APC presents antigen peptides.

25
Q

What is an antibody?

A

A immunoglobulin with glycoproteins that can bind to specific epitopes on antigens. There exists different classes but the IgG is the most common.

26
Q

What are the main roles of antibodies?

A
  1. Neutralization and lysis of microbes and toxins
  2. Opsonization for phagocytosis
  3. antibody-dependent cellular cytotoxicity
  4. Inflammation/complement activation
27
Q

What’s a hypersensitivity reaction?

A

When something normal is recognized as something foreign - allergic reaction. small molecues/ions act as haptens which complex with proteins to activate the T cells - become a inflammation.