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Medical Microbio Exam 2 > Immune System > Flashcards

Immune System Flashcards

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USMLE® Step 1 flashcards
1
Q

Describe the Innate Immune System (what it is, what it is made up of, antigen responsive?, response time?)

A

The innate immune system refers to the body’s initial response to a pathogen.

It includes physical, chemmical, and microbial barriers for pathogens, and also phagocytic cells, specifically macrophages, neutrophils, and dendritic cells.

It is not specific to individual antigens, and it is rapid.

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2
Q

Describe the Adaptive Immune System (what it is, what it is made up of, antigen responsive? response time?)

A

The Adaptive Immune System is the induced specific response to a pathogen.

It includes B and T cells, and the major histocompatibility complex (MHC).

It is antibody-mediated and cell-mediated, and the response is antigen specific.

It also provides long-lasting immunity.

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3
Q

List some physical barriers and how they protect the body against infection (hint: there are 6 physical barriers)

A

Skin - keeps bacteria on you, not in you

Mucous membranes - limits access to tissue and distributes antiviral/ antibacterial proteins

GI system movement - always moving through peristalsis

Ciliated epithelium - moves any inhaled particles back out of the body

Urine flow - flows outside of body

Epithelium tight junctions

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4
Q

List some chemical barriers and how they protect the body against infection (hint: there are 8 chemical barriers)

A

Saliva, sweat, tears, nasal and vaginal secretions - all have antimicrobial peptides (defensins) and enzymes that can kill microbes

Surfactant - lipoprotein produced in the lungs that binds to pathogens, opsonizing them so that they are easier to phagocytize by immune cells

Bile

Gastric acid and other GI secretions

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5
Q

How do microflora act as a microbial barrier and protect the body against infection?

A

Competitors with the “bad” bacteria - prevent pathogens from growing and accessing desired niches

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6
Q

What cells make up the body’s 1st line of defense against pathogens?

A

Macrophages, Leukocytes, Dendritic cells

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7
Q

How do macrophages defend the body against pathogens?

A
  1. They recognize pathogens using receptors.
  2. They phagocytize extracellular material.
  3. They present antigens which help B and T cells recognize and fight the pathogen.
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8
Q

Describe the steps of phagocytosis

A
  1. The bacterium is identified using surface receptors
  2. The bacteria is engulfed through phagocytosis, becoming a phagosome
  3. The phagosome combines with a lysosome, becoming a phagolysosome
  4. The phagolysosome is degraded and the debris is released from the cell through exocytosis
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9
Q

What cells are leukocytes? And how do leukocytes fight against infection?

A

Lymphocytes, monocytes (macrophage precursors), neutrophils, eosinophils (against parasites), and basophils (release histidine to regulate immune response)

Leukocytes are chemically drawn to bacteria through cytokines released by macrophages.

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10
Q

What are neutrophils and how do they fight against infection?

A

TYpe of lymphocytes that reside in the blood

Recruited to the site of infection by cytokines/ chemokines

Kill bacteria 3 ways:
1. They phagocytize the bacteria
2. degranulation through the release anti-microbial compounds
3. Release NETs (neutrophilic extracellular traps)

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11
Q

What are dendritic cells and how do they fight against infection?

A

Immature dendritic cells reside within peripheral tissue, migrate to lymph nodes, mature in deep cortex

Antigen presenting cells - sample antigens and migrate to lymph nodes to activate adaptive immune response

Link between innate and adaptive immune systems

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12
Q

Antibody-mediated Immunity (directed for/ against?)

A

AKA humoral immunity

Directed against extracellular microorganisms

B cells

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13
Q

B cells (where do they originate and migrate? what do they differentiate into?)

A

Originate from stem cells in bone marrow, mature in bone marrow, then migrate to secondary lymphoid tissue

Experience antigen exposure in secondary lymphoid tissue –> Then differentiate into plasma cells (short-lived) and memory cells (long lived)

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14
Q

Plasma cells

A

Produce antibodies

Made from antigen-exposed B cells and antigen-exposed memory cells

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15
Q

Antibodies

A

4 polypeptide chains: 2 identical light chains and 2 identical heavy chains

Heavy and light chains have variable regions and constant region

5 different classes - different classes differ in the constant region of the antibody

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16
Q

IgM

A

Immunoglobulin M

1st immune response

Activate complement proteins

Cannot cross placenta

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17
Q

IgG

A

Immunoglobulin G

2nd immune response, major antibody circulating in plasma

Promote phagocytosis by macrophages

Can cross placenta

18
Q

Primary Antibody Response

A

Following exposure to a new antigen, there is a slow rise in IgM followed by a slow rise in IgG

19
Q

Secondary Antibody Response

A

Following exposure to previously encountered antigen, there is a rapid rise in IgG and slow or no rise in IgM - produced from memory response

20
Q

Positive IgM and Positive IgG means….

Negative IgM and Positive IgG means….

A

Positive IgM and Positive IgG means acute infection

Negative IgM and Positive IgG means past infection or vaccination

21
Q

Function of Antibodies

A

Neutralize extracellular toxins or viruses - coating of extracellular bacteria allows for rapid detection (opsonization) by phagocytes and phagocytosis

22
Q

Diagnosis through Antibodies

To determine if you had immune response to antigen:

A

Measure concentration of antigen specific antibody

23
Q

How to make monoclonal antibody + uses

A

Isolate plasma cell and fuse with myeloma cell to make hybridoma

Monoclonal antibody for therapy

Antibodies for diagnostic testing - Rapid tests, ELISAs/EIA, Westerns

24
Q

What makes up the Lymphatic System and what do they do

A

Lymphs - fluid and cells in lymphatic vessels

Lymphatic vessels - collect and return interstitial fluid to blood; transport immune cells throughout body

Lymph nodes - kidney shaped organs at intervals along lymphatic vessels

25
Q

How are lipids transported through the lymphatic system?

A

Sugars and amino acids are absorbed directly into capillary blood.

However, for lipids, chylomicrons are transported first into the lymphatic vessel that penetrates into each villlus. Chylomicron-rich lymph then drain into the lymphatic system, which rapidly flows into the blood.

26
Q

Blood in our body flows…..

Lymph in our body flows…..

A

Blood in our body flows in a continuous cycle.

Lymph in our body flows in only one direction.

27
Q

Lymphocytes

A

B and T cells

Circulate between blood, lymph, and lymph nodes

28
Q

Primary Lymphoid Tissues

A

Bone marrow (B cells) and thymus gland (T cells)

Responsible for development and maturation of of lymphocytes

29
Q

Seconday Lymphoid Tissues

A

Lymph nodes, tonsils, spleen, GALT, MALT (gut or mucosa associated lymphoid tissue)

Where mature lymphocytes meet pathogens

30
Q

Lymph Nodes

A

Pathogens from infected tissue sites are picked up by lymphatic vessels and arrive at the next lymph nodes (draining lymph node)
–> Architecture and size of nodes change in response to activation of lymphocytes

31
Q

Cell-Mediated Immunity

A

AKA cellular immunity

Involves T lymphocytes, Antigen-presenting cells which present antigens, and Major histocompatibility complex molecules

32
Q

T Cells (where do they originate?)

A

Originate from stem cells in bone marrow –> Mature in in thymus gland –> Migrate to secondary lymphoid tissue

Respond to antigens on surface of cells

Types of T cells: Helper (CD4 T cells) and Cytotoxic (CD8 T cells)

33
Q

CD4 Th1 T cells

A

Produce IFN-gamma, IL-2, and TNF-beta

Evoke cell-mediated immunity and phagocyte-dependent inflammation

34
Q

How do CD4 T cells fight against infection?

A

When the macrophage engulfs and degrades the bacterium, it produces peptides
2. These bacterial petides are then bound by MHC class II in vesicles
3. Bacterial peptides are then transported by the MHC class II to the cell surface
4. CD4 Th1 T cells recognizes the peptide antigen + MHC class II complex and activates macrophage

35
Q

CD4 Th2 T cells

A

Produce Il-4, IL-5, IL-6, IL-9, IL-10, and Il-13

Evokes strong antibody responses (including those of the IgE classes) and eosinophil accumulation, but inhibits several functions of phagocytic cells (phagocyte-independent inflammation)

36
Q

How do CD8 T cells fight against infection?

A
  1. Virus infects cell
  2. Viral proteins are synthesized in cytoplasm
  3. Peptide fragments of viral proteins are bound by MHC class I in the ER
  4. Bound peptides are transported by MHC class I to the cell surface
  5. Cytotoxic CD8 T cell recognizes the complex of the viral peptide with MHC complex I and kills the infected cell
37
Q

How do antigen presenting cells help fight infections? And what cells are considered APCs?

A

Present antigens to T cells

  1. Ingest and process antigens
  2. Display fragments (short peptides) on their surface in association with molecules of MHC

Includes: B cells, dendritic cells, macrophages

38
Q

MHC Class I

A

Expressed on surface of almost every cell

Present antigens to CD8 cytotoxic T cellls

39
Q

MHC Class II

A

Expressed on surface of APCs

Present antigens to CD4 helper T cells

40
Q

Clonal selection

A

Refers to the process by which immune system selects the correct T cell clone

T cells have different specificities based on the T cell receptor expressed on their surface - TCR determines if they are able to recognize the peptide being presented

41
Q

Clonal expansion

A

T cells with the correct TCR will bind to antigen being presented and differentiate into effector T cells (short lived) and memory T cells (long lived, lasting immunity)

Medical Microbio Exam 2 (7 decks)

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