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PHGY 209 > Immunology III > Flashcards

Immunology III Flashcards

1
Q

What is checkpoint inhibition?

A

It is the “shut off” process of the interaction between the helper T cell and the antigen-presenting cell.

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2
Q

By what processes does checkpoint inhibition occur?

A

The T cell replaces the CD28 protein that was linked to the B7 protein on the APC with CTLA4 or PD-1, which deactivates it.

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3
Q

After the helper T cell is activated, the next cell to be activated is the […]

A

B cell

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4
Q

Explain how the B cell gets activated after the helper T cell has been activated.

A

The B-cell must also have a recognition event with the pathogen presented on the dendritic cell. The helper T-cell then interacts with the B cell directly by linking the T cell CD40L proteins with the B cell CD40 protein. The T-cell then releases cytokines, which leads to the activation of the B cell and its production of antibodies.

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5
Q

The activation of the T-cells and B-cells takes place in […]

A

The lymph node and spleen

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6
Q

Why does the B-cell also have to have its own recognition event with the antigen?

A

This is another checkpoint on top of the helper T-cell to avoid an incorrect response.

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7
Q

Explain what happens once the B-cell has been activated.

A

In the lymph node or spleen, the B cell will divide. One will turn into a memory cell, which stays in the organ. The other will divide into two plasma cells, which will produce specific antibodies, which will be secreted into the circulation to fight the pathogen.

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8
Q

Which types of cells produce memory cells?

A

Helper T-cells, B-cells, and cytotoxic T-cells

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9
Q

What are the three events required for the activation of the T helper cell?

A
  1. MHC-II + peptide - TCR
  2. Co-receptor CD28 + B7
  3. Cytokines from antigen presenting cell stimulate the T cell
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10
Q

Recall: when the body is in the process of fighting infection, how will serum protein electrophoresis results differ from normal?

A

The gamma-globulin fraction will be way higher, because antibodies are part of that and are being produced in much higher numbers.

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11
Q

Describe the structure of plasma cells and how that corresponds to their purpose.

A

Plasma cells have a membrane filled with endoplasmic reticulum dedicated to producing thousands of antibodies per minute.

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12
Q

How long do plasma cells live for?

A

Only about a week.

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13
Q

Antibodies, also called […], belong to the group of proteins called […].

A

Immunoglobulins, globulins.

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14
Q

Describe the structure of antibodies.

A

They are made up of 4 polypeptide chains: 2 identical heavy chains and 2 identical light chains. They also have two distinct regions within the heavy and light chains: the FAB region and the Fc region.

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15
Q

Explain what the FAB region is on the antibody.

A

It is the variable region. This is where antigens bind and where the specific recognition event takes place. The sequence will be unique among antibodies based on the pathogen they are recognizing.

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16
Q

Explain what the Fc region is on the antibody.

A

It is the constant region, also called the crystallizable region. It will be identical in sequence for a given class of antibodies.

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17
Q

Antibody class is determined by […]

A

The sequence of the constant region Fc of the antibody

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18
Q

What are the 5 antibody classes?

A

IgG, IgA, IgM, IgD, and IgE.

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19
Q

Describe the structure of the major antibody classes.

A

IgG: Y-shaped with 2 binding sites
IgA: 2 Y’s stuck together with 4 binding sites
IgM: pentamers with 10 binding sites
IgD: Y-shaped with 2 binding sites
IgE: Y-shaped with 2 binding sites

20
Q

What is the most abundant antibody class?

A

IgG

21
Q

What is distinctive about IgE antibodies?

A

They are involved in allergic reactions

22
Q

What is distinctive about IgA antibodies?

A

They are found in mucous membrane-associated tissues

23
Q

What is distinctive about IgM antibodies?

A

They are large with 10 binding sites. This makes them good at activating the complement system, but because they’re so large, they don’t move around the body very well.

24
Q

What is distinctive about IgD antibodies?

A

We don’t know a lot about them.

25
Q

Summarize how antibody-mediated immunity works.

A

It is carried out by B-cells. B cells become activated in the spleen, lymphoid nodule, or lymph node in the presence of a microbe and undergo clonal selection to produce plasma cells, which secrete antibodies, and memory cells which allow a faster response if the antigen is seen again.

26
Q

What is the purpose of memory cells?

A

They allow a faster response by the immune system if the antigen is seen again.

27
Q

What are the two ways in which antibody immunity can be acquired?

A

Actively or passively.

28
Q

Explain what active antibody immunity is.

A

It is when the person’s own immune system responds to a microbe. This leads to long-lasting protection, because it involves the generation of memory cells from the T and B cells.

29
Q

What are the two types of active antibody immunity? Explain the difference between them.

A

Natural: develops when a person is exposed to an antigen by chance
Artificial: develops when a person is purposefully exposed to an antigen

30
Q

What type of antibody immunity is conferred when someone gets a vaccine?

A

Active artificial immunity.

31
Q

What type of antibody immunity is conferred when someone is exposed to the flu virus?

A

Active natural immunity.

32
Q

Explain what passive antibody immunity is.

A

It is when the person receives antibodies from another person or animal, which leads to temporary protection. Memory cells are not involved.

33
Q

What are the two types of passive antibody immunity? Explain the difference between them.

A

Natural: IgG moves from mother to fetus across the placenta, IgA in breast milk after the child is born
Artificial: receive serum containing antibodies from a person or animal that has been vaccinated.

34
Q

What is a vaccine?

A

A vaccine consists of small quantities of living or dead pathogens, small quantities of toxins, or harmless antigenic molecules derived from the microorganism or its toxin.

35
Q

Explain the general principle behind vaccination.

A

Exposure to the antigenic substance results in an active immune response that induces formation of memory cells required for rapid, effective response to future infections by that particular organism.

36
Q

Explain the importance of passive immunity for infants.

A

IgGs from the placenta and IgAs from breast milk are essential sources of protection for infants during the first month of life, when their immune systems are not developed enough to synthesize their own antibodies well enough.

37
Q

What are the 6 major roles of antibodies in fighting infection?

A
  1. Neutralizing antigen
  2. Agglutinating antigen
  3. Precipitating antigen
  4. Activating complement
  5. Opsonization
  6. Antibody-dependent cellular cytotoxicity
38
Q

Explain how antibodies neutralize antigens.

A

By the antibody binding to a bacterial toxin, it can neutralize it. By binding to it, it prevents it from functioning correctly because it changes their structure.

39
Q

Explain how antibodies agglutinate antigens.

A

Antigens can multiple microbes in place, which is important because it slows the spread of the microbes in the body.

40
Q

Explain how antibodies precipitate antigens.

A

If you glue soluble antigens together and cause them to precipitate, they will be held in place and it’ll facilitate their phagocytosis.

41
Q

Explain how antibodies activate complement.

A

When the antigen and antibody find a match, this can activate a complement protein called C1. This triggers the activation of other downstream complement molecules. This leads to the formation of a membrane attack complex (MAC), which is a channel in the microbe that’ll cause the contents of the cell to leak out, killing it. This will also contribute to the killing of cells via opsonization.

42
Q

Explain how antibodies aid in opsonization.

A

They can help the phagocytes recognize what to ingest. On the surface of the phagocytes, they have receptors for the Fc portion of the antibody. This will increase the recognition event via its Fc receptors, leading to its ingestion and more effective phagocytosis.

43
Q

Explain how antibodies contribute to antibody-dependent cellular cytotoxicity.

A

When antibodies bind to specific infected cells, they lead to activation of NK cells to identify and kill the cells of interest.

44
Q

Describe the progression of antibody production after initial exposure to the antigen.

A

It begins low, peaks (relatively low) at around 1 week, and then comes back down shortly after.

45
Q

Describe the progression of antibody production upon subsequent exposure to an antigen.

A

It is very rapid and reaches a very high peak before lowering to a still-high concentration.

46
Q

Explain the difference in the progression of antibody production between initial and subsequent exposure to an antigen.

A

Initially, it takes several days for the antibody system to build up. It peaks at around 1 week, so it’s usually too slow to prevent getting the disease the first time. But because memory cells are produced, they serve as an amplification event for the next time the antigen is encountered. Normally, there are not large pools of cells with receptors for a particular pathogen, as our body is prepared for many different ones. But once you are exposed and the T cells divide, this creates more with those receptors, making the response faster next time.

47
Q

What does it mean for a lymphocyte to gain immunocompetence?

A

It means that they must develop antigen receptors to be able to detect harmful cells.

PHGY 209 (33 decks)

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