Medical Microbiology I > Elements of Host Protective Response (Part 2) > Flashcards

Elements of Host Protective Response (Part 2) Flashcards

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1
Q

Phagocytic cells

A
  • Neutrophils
  • Monocytes
  • Macrophages
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2
Q

Phagocyte types/characteristics

A
  • Myeloid progenitor lineage
  • Granulocyte (monocyte CFU)
  • Polymorphonuclear leukocytes
  • Mononuclear
  • Dendritic Cells
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3
Q

Phagocytosis definition

A
  • Process by which certain cells of the innate immune system (neutrophils & macrophages) engulf large particles, such as intact microbe
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4
Q

Process of phagocytosis

A
  • Cell surrounds the particles with extensions of its plasma membrane
  • Leads to formation of a intracellular vesicle called a phagosome
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5
Q

Chemotaxis

A
  • Movement of a cell directed by a chemical concentration gradient
  • Movement of leukocytes into various tissues directed by gradients of chemokines
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6
Q

Cyotkines

A
  • Secreted proteins that function as mediators of immune and inflammatory reactions
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7
Q

In innate immune responses, cytokines are produced by

A
  • Macrophages

- Natural killer cells

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8
Q

In adaptive immune responses, cytokines are produced by

A
  • Mainly T lymphocytes
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9
Q

Chemokines

A
  • A large family of structurally homologous, low-molecular-weight cytokines
  • Stimulate leukocyte movement
  • Regulate migration of leukocytes from the blood to tissues
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10
Q

Polymorphonuclear leukocytes (neutrophils) important features

A
  • Short-lived
  • Comprise 50% to 70% of circulating WBCs
  • Primary phagocytic defense against bacterial infection
  • Major component of the inflammatory response
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11
Q

Polymorphonuclear leukocytes (neutrophils) physical characteristics

A
  • 9 to 14 μm in diameter
  • Lack mitochondria
  • Granulated cytoplasm in which granules stain with both acidic and basic stains
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12
Q

Polymorphonuclear leukocytes (neutrophils) nucleus

A
  • Multilobed nucleus

- “Segmented” at terminal differentiation

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13
Q

Polymorphonuclear leukocytes (neutrophils) response to infection

A
  • Leave the bloodstream
  • Concentrate at the site of infection in response to chemotactic factors
  • Increase in number in the peripheral blood and include precursor forms
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14
Q

Bone marrow in response to infection

A
  • Production of polymorphonuclear leukocytes (neutrophils) from the bone marrow increases rapidly
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15
Q

Polymorphonuclear leukocyte (neutrophil) production is stimulated by

A
  • Cytokines that are secreted by many cell types in response to infection
  • Act on bone marrow stem cells to stimulate proliferation & maturation
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16
Q

Band forms

A
  • Precursors of polymorphonuclear leukocytes (neutrophils)
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17
Q

Left shift with an increase in bands versus segs

A
  • Increase in band forms in blood count of polymorphonuclear leukocytes (rather than differentiated forms)
  • Major indicator of infection
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18
Q

Polymorphonuclear leukocytes (neutrophils) ingest

A
  • Microbes in the circulation

- Enter extravascular tissue at sites of infection

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19
Q

Polymorphonuclear leukocytes (neutrophils) ingest bacteria by

A
  • Phagocytosis
  • Expose the bacteria to antibacterial substances and enzymes contained in primary (azurophilic) and secondary (specific) granules
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20
Q

Azurophilic granules are enzymes such as

A
  • Myeloperoxidase
  • β-glucuronidase
  • Elastase
  • Cathepsin G
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21
Q

Specific granules (polymorphonuclear leukocytes)

A
  • Lysozyme

- Lactoferrin

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22
Q

Lifespan of polymorphonuclear leukocytes (neutrophils)

A
  • Cells die after a few hours

- Dead neutrophils are the major component of pus

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23
Q

Eosinophils

A
  • Granulocyte of myeloid lineage
  • Heavily granulated (11 to 15)
  • Phagocytic, motile, and granulated
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24
Q

Eosinophil nucleus

A
  • Bilobed nucleus

- Stains with the acid dye eosin

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25
Eosinophil granules contain
- Acid phosphatase - Peroxidase - Eosinophilic basic proteins
26
Role of eosinophils
- Defense against parasitic infections | - Eosinophilic basic proteins are toxic to many parasites
27
Features/functions of basophils
- NOT phagocytic - Release the contents of their granules during allergic responses - Similar chemical mediators as mast cells - Contribute to immediate hypersensitivity reactions
28
Myeloid cells
- Differentiate from myeloid progenitor | - Part of the mononuclear phagocyte system
29
Mononuclear phagocyte system consists of
- Monocytes in the blood | - Cells derived from monocytes in tissues
30
Different cytokines or tissue environments promote myeloid stem cells and monocytes to
- Differentiate into the various macrophages and dendritic cells
31
In the lungs, myeloid stem cells and monocytes differentiate into
- Macrophages | - Alveolar macrophages
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In the liver, myeloid stem cells and monocytes differentiate into
- Kupffer cells
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In the kidneys, myeloid stem cells and monocytes differentiate into
- Intraglomerular mesangial cells
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In connective tissues, myeloid stem cells and monocytes differentiate into
- Histiocytes
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In bone and joints, myeloid stem cells and monocytes differentiate into
- Osteoclasts | - Synovial cells
36
In the brain, myeloid stem cells and monocytes differentiate into
- Microglial cells
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Characteristics of monocytes
- 10 to 18 μm in diameter - Single-lobed, kidney bean-shaped nucleus - Represent 3% to 8% of peripheral blood leukocytes - Less abundant than neutrophils
38
Monocyte functions
- Follow neutrophils as an early cellular component of inflammation - Ingest microbes in the blood and tissues - Unlike neutrophils, when entering extravascular tissues they survive for a longer time & further differentiate into macrophages
39
Characteristics of macrophages
- Long-lived cells that are phagocytic - Contain lysosomes - Unlike neutrophils, have mitochondria
40
Main functions of macrophages
- Phagocytosis - Antigen presentation to T cells to initiate specific immune responses - Secretion of cytokines to activate & promote innate immune responses
41
Macrophages express cell surface receptors for
- Fc portion of immunoglobulin (Ig) G | - C3b product of the complement cascade (CR1, CR3)
42
Macrophage receptors facilitate
- Phagocytosis of antigen, bacteria, or viruses coated with their respective proteins (IgG, CR1, CR3)
43
Pattern-recognition receptors of macrophages
- Recognize pathogen-associated molecular patterns | - Activate protective responses
44
Macrophages expresses the class II MHC antigen
- Allows these cells to present antigen to CD4 helper T cells to expand the immune response
45
Macrophages secrete
- Interleukin-1 - Interleukin-6 - Tumor necrosis factor - Interleukin-12, etc. - Stimulates immune & inflammatory responses (such as that seen in fever)
46
Macrophages respond to interferon-γ
- T-cell derived cytokine that activates macrophages
47
Activated macrophages
- Enhanced phagocytic, killing, and antigen-presenting capabilities
48
Macrophages function as receptors for
- Bacterial components, antibodies, complement
49
Macrophages promote
- Activation & hagocytosis of antigen
50
Macrophage receptors promote
- Antigen presentation | - Activation of T-cells
51
Mononuclear phagocytes arise from
- Precursors in the bone marrow - Circulating blood stage is the monocyte - Phagocytic vacuoles and lysosomes
52
In the tissues, mononuclear phagocytes become
- Macrophages - May be activated by microbes - May differentiate into specialized forms that are resident in different tissues
53
The electron micrograph of a portion of an activated macrophage shows
- Numerous phagocytic vacuoles | - Cytoplasmic organelles
54
Dendritic cells
- Myeloid and lymphoid origins - Octopus-like tendrils - Professional Antigen Presenting Cells (APCs) that can also produce cytokines - Important bridge between innate and adaptive immunity
55
Types of dendritic cells and where they are found
- Langerhans cells in the skin - Dermal interstitial cells - Splenic marginal dendritic cells - Dendritic cells in the liver, thymus and germinal centers of the lymph nodes
56
Plasmacytoid dendritic cells
- Present in blood | - Produce large amounts of interferon alpha & cytokines in response to viral & other infections
57
Follicular dendritic cells
- Present in lymph nodes & spleen - Not hematopoietic in origin - Have tendrils and a "sticky" surface to concentrate & present antigens to B cells
58
Immature dendritic cells
- Capture and phagocytose antigen efficiently
59
Main functions of immature dendritic cells
- Release cytokines to activate and steer the subsequent immune response, and then mature into dendritic cells - Move to lymph node regions rich in T cells to present antigen on class I and class II MHC antigens
60
Dendritic cells are the only antigen-presenting cell that can
- Initiate an immune response with a naïve T lymphocyte and also determine the type of response
61
Lymphocytes differentiate from
- Lymphoid progenitor cells
62
Physical characteristics of lymphocytes
- 6 to 10 μm in diameter - Smaller than leukocytes - Large nucleus and smaller, agranular cytoplasm
63
2 major classes of lymphocytes
- B cells | - T cells
64
B and T cells are indistinguishable by
- Morphologic features | - Basis of function and surface markers
65
Natural killer (NK) cells
- Lymphoid cells that are not B or T cells (non-B/non-T cells, or null cells) - Large, granular lymphocytes (LGLs)
66
Primary function of B cells
- Make antibodies
67
General functions of B cells
- Internalize antigen - Process the antigen - Present the antigen to T cells to expand the immune response
68
B cells can be identified by the presence of
- Immunoglobulins - Class II MHC molecules - Receptors for the C3b and C3d products of the complement cascade (CR1, CR2) on their cell surfaces
69
The B-cell name is derived from
- Site of differentiation in birds | - The bursa of Fabricius and the bone marrow of mammals
70
B-cell differentiation also takes place in fetal
- Liver & spleen
71
Activated B cells either develop into
M-emory cells (express the CD45RO cell surface marker) | - Circulate until activated by specific antigen, or terminally differentiate into plasma cells
72
Plasma cells
- Small nuclei - Large cytoplasm - Producers of antibody
73
T cells acquired their name because
- They develop in the thymus
74
Two major functions of T cells in response to foreign antigen
- Control, suppress (when necessary), and activate immune & inflammatory responses by cell-cell interactions & by releasing cytokines - Directly kill virally infected cells, foreign cells (tissue grafts), and tumors
75
T cell content
- Make up 60% to 80% of peripheral blood lymphocytes
76
T cells were initially distinguished from B cells on the basis of
- Their ability to bind and surround themselves with sheep erythrocytes through the CD2 molecule (forming rosettes)
77
All T cells express
- Antigen-binding T-cell receptor (TCR) that resembles but differs from antibody - CD2- and CD3-associated proteins on their cell surface
78
T cells are divided into 3 major groups on the basis of
- Type of TCR - Cell surface expression of two proteins (CD4 and CD8) - Most lymphocytes express the αβ TCR
79
CD4-expressing T cells are primarily
- Cytokine-producing cells
80
Functions of CD-4expressing T cells
- Help initiate and mature immune responses - Activate macrophages to induce delayed-type hypersensitivity responses (DTH) - A subset of these cells suppress responses
81
CD4 T cells can be further divided into
- TH0, TH1, TH2, TH17 & Treg subgroups | - According to the spectrum of cytokines they secrete and the type of immune response that they promote
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TH1 cells
- Promote local, antibody and cellular inflammatory, and DTH responses
83
TH2 cells
- Promote antibody production
84
TH17 cells
- Activate neutrophil responses
85
Treg cells
- Promote T-cell tolerance
86
CD8 T cells also release cytokines, but are better known for
- Ability to recognize & kill virally infected cells, foreign tissue transplants (non-self-grafts), and tumor cells as cytotoxic killer T cells - Also suppress immune responses
87
T cells also produce memory cells that express
- CD45RO
88
Terminally differentiated effector CD4 and CD8 T cells express
- Class II MHC antigen
89
A variable number of T cells express the γδ TCR but do not express
- CD4 or CD8
90
T cell lymphocytes generally reside in
- Skin & mucosa and are important for innate immunity
91
NKT cells
- T cells which share characteristics with NK cells
92
Large, granular lymphocyte NK cells resemble
- CD8 T cells in cytolytic function toward virally infected and tumor cells - Differ in mechanism for identifying target cells
93
NK cells also have Fc receptors, which are used in
- Antibody-dependent killing | - Also called antibody-dependent cellular cytotoxicity (ADCC or K) cells
94
Cytoplasmic granules of T cells contain
- Cytolytic proteins to mediate the killing
95
Innate immunity
- Mediates the initial protection against infections - Relies on mechanisms that exist before infection - Capable of rapid responses to microbes, and react in essentially the same way to repeat infections
96
Adaptive immunity
- Develops more slowly | - Mediated by lymphocytes and is stimulated by exposure to infectious agents
97
Neutrophil nickname
- Trash collector and disinfector | - Very effective at phagocytosis and killing bacteria
98
Dendritic cell nickname
- Billboard display | - Phagocytoses antigen & brings it to the lymph node to display to CD4 & CD8 T cells
99
Macrophage nickname
- Pac man - Phagocyte which is activated by interferon-γ & then becomes efficient at killing phagocytized microbes and producing cytokines
100
Lymph node nickname
- Police department - Repository for B and T cells - Evidence of infection is brought by the lymphatics or dendritic cells & other antigen presenting cells to the lymph node to activate the T cells to communicate with other cells through cytokines (like a radio) to be dispatched to take care of the problem
101
CD4 T cell nickname
- Desk sergeant/dispatch officer - Presented with the microbial problem by antigen presenting cells, it tells other cells to take care of the problems by producing cytokines
102
CD8 T cell nickname
- "Cop on the beat"/patrol officer - Activated in the lymph node & then moves to the periphery to patrol for virus infected or tumor cells - Then grabs the perpetrator and inactivates it
103
B cell nickname
- Product design and building company | - Pre-B cells and B cells alter the DNA of their immunoglobulin genes to produce the plans for a specific immunoglobulin
104
Plasma cell nickname
- Factory | - Immunoglobulin-producing factory with a small office (nucleus) and many assembly lines (ribosomes) for making antibody
105
Mast cell nickname
- Activatable chemical warfare unit | - Fc receptors for IgE that will trigger the release of histamines and other agents upon binding to an allergen signal
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