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Pathogenic Microbiology > Lecture 5 > Flashcards

Lecture 5 Flashcards

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1
Q

What is the difference between innate and adaptive immunity?

A

Innate immunity: Receptors recognize conserved structures present in many pathogens (Pathogen-associated Molecular Patterns): LPS, peptidoglycan, lipids, mannose, bacterial DNA and viral RNA
Adaptive immunity: Receptors recognize a specific structure unique to that pathogen, and has “memory”

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2
Q

What are the features of adaptive immune responses?

A 
specificity, 
diversity, 
memory, 
clonal expansion, 
specialization, 
contraction and homeostasis, 
and non-reactivity to self
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3
Q

What are lymphocytes?

A

Mediators of adaptive immune responses; only cells with specific receptors for antigens (e.g., T-cells, B-cells)

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4
Q

What are Antigen-presenting cells APC, and what is its role?

A

Specialized to capture, concentrate, and display antigens for recognition by lymphocytes
ex: Dendritic cells; macrophages, B-cells; follicular dendritic cells

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5
Q

What are effector cells, and what is its role?

A

Function to eliminate microbes; includes lymphocytes, granulocytes (neutrophils, eosinophils), macrophages

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6
Q

What are the 2 arms of adaptive immune response?

A

Humoral: antibodies (proteins produced by B-cells) that circulate in the blood. Antibodies can recognize the infected cells and free microbes (bacteria and viruses).
Cellular: Lymphocytes (T-cells) that do not produce a soluble product. T-cells can recognize the infected cells, but not free microbes.

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7
Q

Describe the lymphocyte antigen receptor of B and T-cells.

A

The B-cell antigen receptor is a membrane-bound antibody - SURFACE IMMUNOGLOBULIN.
The T-cell antigen receptor IS NOT membrane bound antibody but a distinct molecule - T-CELL ANTIGEN RECEPTOR
Each antigen receptor binds to a different antigen and Each cell has only one antigen specificity

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8
Q

What is the structure of T-cell receptors?

A

T-Cell Receptors for Antigens Consist of 1 Alpha Chain and Beta Chain Linked by a Disulfide Bridge

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9
Q

What are MHC molecules?

A

Are encoded by a family of genes called the major histocompatibility complex to which t-cells bind
infected cells produce MHC molecules that binds to antigen fragments and then are transported to the cell surface in a process called antigen presentation

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10
Q

What are the 2 different classes of MCH (HLA) molecules?

A

MHC Class I – Universal, located in the ER membrane

MHC Class II – Specialized cells (macrophages, dendritic cells, B-cells), located in the cytoplasm

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11
Q

What is the difference between MHC class 1 and 2?

A

MHC-1 has longer alpha chain that is membrane bound, but does not have a beta that is membrane bound
both classes process and bind to peptide

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12
Q

What are central lymphoid organs?

A

THYMUS – T cell maturation

BONE MARROW – B cell maturation

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13
Q

What are peripheral lymphoid organs?

A

LYMPH NODES
SPLEEN WHITE PULP
MUCOSA-ASSOCIATED LYMPHOID TISSUE

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14
Q

Describe progenitor cells in the thymus.

A 
P-cell progenitor undergoes maturation and gives rise to different t-cells with different receptors on it. The body has to decide which are useful among them…it undergoes positive and negative selection. Less than 1% is selected and the rest is nuclear apoptosis (about 3-4 days) 
Positive – test all t-cells for ability to bind MCH class molecules with an antigen bound to it…if it can't bind at all, it gets eliminated 
You want to have a binding that is low to intermediate. If you have binding that is too tight then the negative selection comes into play --> too strong of binding, then the t-cells can become active against our own bodies 
Negative – if the binding is really strong of t-cells to MCH class molecules
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15
Q

What is lymphocyte amplification AKA Adaptive immunity?

A

Adaptive immunity has capacity to increase its number of the functional/effector cells to keep up with the number of microbes In the body to eliminate the pathogen

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16
Q

describe lymphatic release of antibodies.

A

Lymphocytes can release antibodies that can bind directly to circulating pathogen and can lead to the neutralization to the microbe, preventing it from interacting with the host cell.
Antibodies can also activate the complement system or decorate the surface of the antigen so that can be detected by macrophages and be gobbled up and destroyed

17
Q

Describe differentiation of lymphocytes.

A

Once you go through differentiations and have specialized T-cells, you can have H(helper) t-cells.
Helper cells have the macrophage antigen, and the t-cells to it, and it releases cytokines to activate macrophages to help fight off the infection. It can also signal other t-cells and b-cells.
Cytotoxic lymphocytes - Engage the effector cells by engaging the surface molecule presented in the antigen. The CTL directly kills the effector cell in this case.
Both are examples of cellular base immunity

18
Q

What is the role of T-helper cells, cytotoxic t-lymphocytes, and plasma cells?

A

t-helper- activates b-cells and macrophages, and releases cytokines
cytotoxic t-lymphocytes - kill virus-infected cells
plasma cells - produce antibodies

19
Q

What is the difference of activation of TH2 and TH1?

A

TH2 – get activated by B-cells,

and TH1 - by macrophages

20
Q

Describe TH1 and TH2 cell activity.

A 
TH1 – Macrophages and antigen-presenting cells. We have bacteria and the Micro comes in and starts chopping up microbe into pieces, and it loads them into MHC class 2 molecules (has this in addition to class 1) which get transported to the surface of the cell. 
MCH1 gets recognized by t-helper type 1 that releases signaling molecules that can act on infected cell, get it activate and help it get rid of the antigen. 
The same is happening in the surface of a B-cell for TH2
21
Q

Why are antibodies limited in function?

A

Antibodies limited in function because of their location…they aren’t good at clearing up intercellular pathogens cus they can’t get to them

22
Q

What is the purpose of clonic selection of B-cells?

A

Clonal selection of B cells generates a clone of short-lived activated effector cells and a clone of long-lived memory cells

23
Q

What is the job of dimer cells?

A

to produce antibodies (along with the plasma cells)

24
Q

What is the purpose of antibodies sticking around after fighting off infection?

A

Some antibodies stick around and serve as memory cells so the next time the antigen comes in, you will get a more rapid response
Antibodies have specific receptors that it can only recognize antigens for the receptor

25
Q

What does the clonal selection theory account for?

A

Diversity – information coding for all Abs is in DNA
Self/non-self discrimination – eliminate cell clones bearing all self-reactive receptors on their surface or inactivate them
Memory – increase in number of cells the second time around

26
Q

Describe the structure of antibodies (immunoglobulins)

A

2 long chains – heavy, and 2 shorter – light chains connect through disulfide bonds
Heavy chains have variable regions b/c the sequence varies that bind the antigen. Varying allows binding capacity to increases.
Fab fragment – antigen binding region
FC region – fragments that are constant and invariant in the antibody, and have receptor functions

27
Q

What are the five classes of antibodies and their functions?

A

IgD – unknown function
IgG – major form of antibody circulating in blood
IgM – Membrane-bound form of IgM is the receptor on B cells. IgM also circulates in the blood
IgE – Involved in allergic reactions and defense against parasites
IgA – Found in secretions (e.g., mucosal surfaces, the gut, tears). Serves as first line of defense against pathogens

28
Q

What is the difference between IgM and IgG?

A

IgM primarily acts as an activator of the complement system.
IgG can also do this but in addition it can call into play further effector mechanisms via the Fc receptors on phagocytes, eosinophils and mast cells.

29
Q

What is the difference in antibody arrangement between mature and immature B-cells?

A

Antibody sequences in mature B cells will be rearranged Antibody sequences in immature B cells will be unrearranged (same as DNA in any other cell).

30
Q

What are the variable regions of heavy and light chains??

A

Heavy chains - V, D, J

light - only V and J

31
Q

What is VDJ recombination?

A

For each antibody chain, each B cell chooses (pretty much at random) one of each kind of segment and pastes them together. Creates a huge amount of potential diversity without devoting a lot of DNA to antibody genes.

32
Q

What are naive b-cells?

A

Expresses a membrane-bound antibody (IgM) on its surface (so has undergone DNA rearrangement), but has not yet encountered antigen

33
Q

What is somatic hypermutation?

A

mutations in the V regions of the gene that results in higher binding of the gene

34
Q

What are the 2 ways by which antibodies operate?

A
  1. Can block entry of a microbe into a host cell or prevent virus from replicating (neutralizing antibodies)
  2. Can tag invaders for destruction:
    A. By complement – binding of IgM or IgG to repeated epitope on invader surface triggers “classical” pathway
    B. By NK cells: Fc receptors on NK cells bind to exposed Fcs to activate antibody-dependent cellular cytotoxicity (ADCC)
    C. By macrophages: antibodies opsonize (decorating the surface of) invaders
35
Q

What are the ways antibodies do not suffice for defense against pathogens?

A
  1. Viruses tend to rapidly mutate, so if the antibody that is produced for that one type of virus cannot recognize this new type of virus. A good example of this in influenza.
  2. once a pathogen enters a cell, antibodies can’t access it, so it can make thousands of copies of itself
36
Q

describe how To create single body that can recognize a particular antibody of that protein

A
  1. Take b-cell of mice and Fuse them with myeloma cells (immortal cancer cells), and grow them in a HAT medium.
  2. The myeloma cells used lacked HFPRT enzymes, but the b-cells being used do. Any myeloma cells that didn’t fuse with the HAT medium will die because they don’t have the HGPRT enzyme.
    3b. Any b-cells that did not fuse with myeloma will die as well because they can’t survive in the tissue culture, thus you’re essentially forcing only diffuse type of myeloma to survive because they have the property of that enzyme to survive and propagated to survive in that tissue culture.
  3. Clones will produce different antibodies, and some wont be kept because not all the antibodies have the same affinity and strength of binding, thus you can produce immortal cell line

Pathogenic Microbiology (12 decks)

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