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Clin Med I Final Review > Immunology > Flashcards

Immunology Flashcards

1
Q

What is the innate immune system?

A 
First line of defense against bacteria, viruses, and parasites
RAPID response (min to hours)
NON-SPECIFIC defense (attacks all foreign antigens in the same way)
NO memory defense
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2
Q

Physical barriers are part of the ________ immune system

A

Innate (Natural)

Examples:
Lysozyme in tears/other secretions
Skin surface, fatty acids, and normal flora 
Rapid pH change between stomach/intestines
Cilia in nasopharynx
Mucus lining in trachea
Stomach pH of 2
Normal gut flora
Flushing of urinary tract
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3
Q

The complement system is a group of 30+ ________________ that activate in a cascade-like manner in response to _________.

A

30+ plasma proteins, in response to an antigen (anything foreign to body)

It enhances (“compliments”) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism

Promotes inflammation to help clear infection

Attacks the pathogen’s cell membrane —> lysis

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4
Q

Sequence of events in the complement pathway

A
  1. Activation through either the classical, let in, or alternative pathways (most common)
  2. Formation of the enzyme C3 convertase (cleaves C3)
  3. Opsonization and phagocytosis
  4. Inflammation
  5. Membrane Attack Complext (MAC) formation and lysis
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5
Q

The three pathways of the complement system:

A
  1. Classical Pathway - triggered by antibodies (such as IgM and IgG) binding to an antigen; most responses use this pathway
  2. Lectin Pathway: lectin proteins bind to mannose residues on the microbial surface
  3. Alternative Pathway: complement proteins act directly on cell surfaces (unusual)
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6
Q

The most abundant complement protein is _______.

A

C3

C3 convertase cleaves C3 to activate the classical pathway

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7
Q

The coating of a microbe by an antibody (or complement protein) to “tag” it for phagocytosis is called:

A

Opsonization

Marks the cell for destruction

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8
Q

Phagocytosis is the mechanism by which host cells:

A

Engulf and destroy an organism (some phagocytes are better than others)

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9
Q

The final step in the classical pathway of the complement system is the formation of the _________________

A

Membrane Attack Complex (MAC) —> Lysis

MAC is a complex of complement proteins that form to cause the lysis of a microbe

C5b, C6, C7, C8, and C9 are the proteins that bind to form MAC

Once these proteins combine on the surface of an antigen, the cell wall disintegrates and cell rupture ensues

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10
Q

________________ is an autoimmune disease that is also a huge player in complement deficiencies

A

SLE

*Same deficiencies seen in pyogenic infections

C1,C2,C4 deficiency —> deficiency in cleanup of IC and activation of classical pathway

C3 deficiency —> inability of cleanup of IC, complement activation

Factor H deficiency —> loss of control in the activation of alternative pathway, low C3 concentrations

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11
Q

Stages of an inflammatory response

A
  1. Tissue Damage
  2. Chemical signals alert endothelial cells along the capillary wall
  3. Neutrophils become “sticky” and stop rolling along the capillary wall
  4. Mast cells release histamine
  5. Histamine causes vasodilation and openings in between endothelial cells
  6. Fluid and leukocytes enter the affect tissu
  7. Neutrophils “squeeze” through endothelium (“extravasation”)
  8. Neutrophils are attracted to the damaged site and ingest/destroy bacteria

*Neutrophils = professional phagocytes (monocytes = 2nd line)

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12
Q

Neutrophils, eosinophils, and basophils are _______________

Monocytes and Lymphocytes are _________________

A

Granulocytes; Agranulocytes

Granulocytes have granules (packets of histamine, lysosymes, etc to help breakdown things)

Monocytes are the most important agranulocytes

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13
Q

Never Let Monkeys Eat Bananas

A

The distribution of WBCs in descending order:

Neutrophils (62%)
Lymphocytes (30%)
Monocytes (5%)
Eosinophils (2.5%)
Basophils (0.5%)
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14
Q

All about the Neutrophils!

A

The most abundant WBC - the body’s first responders

Particularly active against bacteria

Adhere to the vascular endothelium using adhesion molecules

“Squeeze” out into the tissue to attack bacteria

Undergo phagocytosis very efficiently to kill antigens

Promote inflammation

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15
Q

Increased neutrophils on the WBC diff is suggestive of…..

A

An acute bacterial infection, particular if bands (immature neutrophils) are high

An increase in BAND neutrophils means that the bone marrow has been signaled to release more WBCs and can be described in lab values as LEUKOCYTOSIS WITH A LEFT SHIFT

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16
Q

______ signifies a “left shift”

A

> 8% bands (immature neutrophils)

Indicative of an acute bacterial infection

Typically, bands only make up 3-6%

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17
Q

Elevated neutrophil count is called …

A

Neutrophilia

Causes:
• Acute bacterial infection (also fungal, viral, parasitic, spirochete)
• Noninfectious inflammation (hypersensitivity rxn, postop state, acute gout
• Metabolic: DKA, uremia, preeclampsia
• Other: exogenous corticosteroids

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18
Q

Low neutrophil count is called …

A

Neutropenia

Defined by the absolute neutrophil count (ANC)

Causes: 
• Infection (esp VIRAL)
• Bone Marrow disease
• Radiation therapy
• Chemotherapy drugs
• Toxins
• Hereditary
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19
Q

_____________ are WBCs that play a role in allergic and antigen response

A

Basophils

Release granules that contain:

  1. HISTAMINE (increases blood flow to area)
  2. Heparin (reduces clotting)
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20
Q

____________ target larger parasites (ie Helminths) that are too large for one WBC to phagocytize

A

Eosinophils

Modulate allergic inflammatory response (help the basophils)

Rare in blood but numerous in the mucous membranes of the respiratory, digestive and lower urinary tracts

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21
Q

__________ are early responders in Type I allergies

A

Mast Cells

Release histamine and heparin

Present in barrier tissues (mucosa)

Play important roles in allergy and ANAPHYLAXIS reactions (think Type I hypersensitivity)

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22
Q

Largest WBC

A

Monocytes

Found in the blood and SPLEEN

Monocytes migrate into the tissues to become:
• Macrophages
• Dendritic Cells

Why you get splenomegaly with a MONONUCLEOSIS infection

Monocytes are themselves agranulocytes but can differentiate into macrophages, which are granulocytes

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23
Q

The three different types of Lymphocytes

A

B-cells
T-cells
Natural Killer Cells

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24
Q

The two primary lymphatic organs are ________ and _________

A

Bone Marrow - formation of B and T cells and site of B cell maturation

Thymus - site of T cell maturation

25
Secondary lymphatic organs are where lymphocytes __________
Encounter antigens (shouldn’t occur in primary lymphatic organs because they are sterile) Spleen - removes old blood cells, synthesizes antibodies, removes antigens by way of blood and lymph circulation, stores extra RBCs Lymph Nodes - filter foreign molecules and cancer cells (why we see LAD in cancer) Tonsils/Adenoids - filter bacteria and viruses Mucosa-Associated Lymphoid Tissue (MALT) - regulates mucosal immunity
26
What’s so special about bone marrow?
Located in the spongy inner portion of bone Location of hematopoiesis Primarily located in the pelvis, ribs, vertebrae, and sternum Hosts B CELL maturation
27
Ok, so what about the Thymus?
Located in the mediastinum, behind the sternum Larger as a child, shrinks with age (by age 4, it’s 2% of original size) Hosts T CELL maturation
28
Thymus sail sign
Sail like shadow in right upper chest on X-ray of a child Benign - it’s just the thymus (which you don’t see on adults)
29
So spleens are cool too. What do they do?
Largest lymphoid organ Removes old blood cells, holds storage of RBCs, recycles iron Synthesizes antibodies, specifically IgM memory cells (made after first exposure to an antigen)
30
So what happens when you don’t have a spleen
Asplenia Modest increase in circulating WBCs/platelets Diminished response to some vaccines Increased susceptibility to infection by ENCAPSULATED BACTERIA: 1. Streptococcus pneumoniae 2. Haemophilus influenzae 3. Neisseria meningitides (B/c complement not effective at labeling these for phagocytosis due to outer capsule) ***Immunize before surgical removal if possible
31
What’s the point of all these damn lymph nodes?
Small 1mm to 1-2 cm in size Encapsulated by connective tissue Filter foreign molecules and cancer cells Become enlarged with certain diseases
32
Yay Tonsils!
First line of defense against ingested or inhaled pathogens Combat common respiratory illnesses such as the common cold Pharyngeal tonsils = adenoids Palatine tonsils Lingual tonsils
33
Mmmmm MALT
Mucosa-Associated Lymph Tissue System of small concentrations of lymphoid tissue found in various submucosal sites Populated by B cells and T cells, plasma cells and macrophages Specializes in antigens passing through the mucosal epithelium Acts by sampling antigen and delivering it to the lymphoid tissue NALT (nasal), BALT (bronchial), and GALT (gut)
34
How is adaptive immunity different from innate immunity?
Second line of defense Highly specific Memory defense
35
The ability to distinguish _______ vs _________ is important because of the destructive nature of the adaptive immune system
Self vs Non-self (foreign antigens) Autoimmune diseases arise from the loss of this ability The innate immune system only activates the adaptive immune system if needed (if foreign cells present)
36
Define humoral immunity
Mechanisms: Antibody-mediated Cell type: B-lymphocytes Mode of Action: Antibodies in circulating serum Purpose: Primary defense against extracellular pathogens (circulating viruses/bacteria)
37
Define cell-mediated immunity
Mechanism: Cell-mediated Cell type: T-lymphocytes Mode of action: Direct cell to cell contact or secreted soluble products Purpose: Primary defense against INTRACELLULAR pathogens (viruses, fungi, intracellular bacteria, TUMOR ANTIGENS)
38
So let’s talk about this B-lymphocytes some more...
B cells are made in the Bone marrow, mature in the Bone marrow Once mature, these mature naive B-cells enter blood circulation and migrate to the secondary lymphatic organs (spleen, lymph nodes, MALT) B-cells will produce specific antibodies to fight against particular antigens ONCE THEY’VE BEEN ACTIVATED
39
Steps to activating B-lymphocytes
1. Recognition: Antigen binds to the mature, naive B-lymphocyte surface receptor 2. Proliferation: B-lymphocytes proliferate and make clones 3. Differentiation: Clones will either become a plasma cell or a memory cell (plasma cells die quickly, memory cells stick around for months/years) —> years later, memory B cells can activate a secondary immune response
40
So what exactly ARE antibodies?
Plasma cells produce antibodies (aka immunoglobulins (Ig), aka gammaglobulins) Antibodies “tag” antigens to mark them for destruction (opsonization) Destruction is via phagocytosis or chemotaxis
41
The five different classes of antibodies, in the order they appear when encountering antigens
``` IgM IgG IgA IgE IgD ``` (Methinks Great Americans Eat Donuts)
42
IgM antibodies
The first responder - first antibody produced by the plasma cells Indicates acute/recent infection LARGE - 5 Y-shaped molecules connected in star shape IgM is very good at activating the complement system 5-10% of antibodies in blood 5-10 day half-life
43
IgG
Second responder - second antibody produced by the plasma cells IgM levels fall as IgG levels rise IgG is good at opsonization IgG can also activate the complement system 75% of antibodies in the blood (MOST ABUNDANT) 21 day half-life - indicate acute/subacute infections
44
IgA
(2 linked Y-shaped molecules) IgA is found primarily in the mucosal membranes and secretions (as secretory IgA) Present in the GI tract, respiratory tract, saliva, sweat, and tears Good at eliminating pathogens through mucosa IgA is a weak opsonizer and is not effective in activating the complement system
45
IgA disorders
IgA Nephropathy: deposition of IgA in the kidneys Henoch-Schonlein Purpura: IgA vasculitis caused by deposition of IgA in small vessels Celiac Disease: presence of IgA anti-endomysial antibodies IgA Pemphigus: IgA antibodies that target proteins in the skin, causing autoimmune blistering disorder
46
IgE
Produced in response to allergens Defends against helminths (roundworms) and parasites IgE bind to mast cells IgE causes the release of histamine Plays a large role in Type I Hypersensitivity Reactions Hang with eosinophils and mast cells
47
IgD
Involved primarily in the activation of B-cells Not very well understood and is thought to play a small role in several different immune processes
48
So how do vaccines work anyway?
Vaccines are a form of acquired immunity that allows us to target specific diseases Vaccines introduce an antigen that stimulates the body to produce antibodies Memory cells are there if the antigen tries to reattack in the future
49
What is Cell-Mediated Immunity
Cell-mediated immunity deals with INTRACELLULAR bacteria, viruses, and any bacteria that are out of reach of antibodies T-lymphocytes are made in the bone marrow but mature in the Thymus Once mature, T-cells express surface receptors, known as T-cell receptors (TCRs) Mature naive T-cells must undergo a 2-signal activation
50
Steps to activating T-lymphocytes
1st signal: TCR binds to the MCH-antigen complex of antigen-presenting cell (APC) 2nd signal: T-cell surface receptor CD28 must bind with B7, located on the APC
51
Activated T-cell functions
Once T-cells are activated, they divide (proliferate) They then differentiate into Helper T-cells, Cytotoxic T-cells, Suppressor T-cells, and Memory T-cells Helper T-cells produce cytokines that stimulate macrophages for phagocytosis Cytotoxic T-cells kill virus-infected and tumor cells
52
Types of T-cells: Helper T-cells
Stimulate B-cells, stimulate T-cells to proliferate, activate macrophages, activate NK cells Surface receptors: CD4+ Binds to MHC II
53
Types of T-cells: Cytotoxic T-cells
Aka Natural Killer Cells Kill virus-infected cells, kill tumor cells Surface receptor = CD8+ Binds to MHC I
54
Types of T-cells: Suppressor T-cells
“The regulator” Prevent immune system over activity by helping recognize self from non-self No surface receptors Does not bind to MHC complex
55
Types of T-cells: Memory T-cells
“The Veteran” Recognizes antigens from previous exposure No Surface receptors Does not bind to MHC complex
56
Antigen Presenting Cells
Essential for adaptive immunity Can be any nucleated cell in the body except for T-cells Their function is to prepare an antigen and present it to the T-cells Antigen Presenting Cells (APCs) have Major Histocompatibility Complexes (MHCs) on their surfaces that display the antigen to the T-cell receptors on cytotoxic and helper T-cells
57
MHC I binds to _______ on ____________ T cells
CD8+ Cytotoxic T cells (Natural Killer Cells) MHC I are found on the surface of all nucleated cells
58
MHC II binds to _______ on ____________ T cells
CD4+ Helper T-cells MHC II are only found on the surface of B-cells, dendritic cells, and macrophages (all produced by the immune system itself)

Clin Med I Final Review (5 decks)

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