Microbiology Module 3

Immune system

It serves as the defense system against infectious diseases and foreign antigens

Immune response

A response generated against a potential pathogen

Innate immunity

The first line of defense, which is nonspecific to the invading pathogen, is rapidly mobilized at the initial site of infection but lacks immunologic memory

Adaptive immunity

The second defense system

Antibody

A protein that is produced in response to a particular pathogen

Antigen

The substance that produces the production of antibodies

Innate immunity

Is an immediate response to a pathogen that does not confer long-lasting protective immunity

Immune components that are important in the adaptive immune response

Phagocytic cells
Natural killer cells (NK)
Toll-like receptors (TLRs)
Cytokines
Complement

Innate immune response

is effective and critical in eliminating most pathogens

Innate immunity

Non-specific defense system and includes barriers to infectious diseases such as the skin and mucous membrane.

Skin

Inhibits the growth of pathogen

Epithelial cell layer

has tight junctions and produces a number of powerful antimicrobial peptides that help provide

Defensin

• Another major peptide of innate host defense with antimicrobial properties

• Are positively charged peptides located primarily in the GI and lower respiratory tracts that created holes in bacterial cell walls and hence disrupt the bacterial membrane.

Mucus

A complex mixture of mucins, proteins, proteases, and protease inhibitors, is a major component of the mucosal epithelium

Acidity of the stomach

Proteolytic enzymes

• GI tract has mechanisms to inhibit bacteria

• The small intestine make this environment hostile to many bacteria.

Polymorphonuclear neutrophilic leukocytes (neutrophils)

Marcrophages along with NK cells

Are the primary cellular components to combat microbes.

interleukin-1 (1L-1)
tumor necrosis factor-alpha (TNF-a)
interleukin-6 (IL-6)
interferons (IFNs)

cytokines that are pro-inflammatory molecules (4) and are induced through TLR interactions.

Where is the epithelial cell layer present

Skin

GI tract
Genitourinary tract

Lysozyme

Is an example of a antimicrobial peptide that dissolves some bacterial cell walls

During infection, circulating phagocytic cell increase and can participate in (4)

chemotaxis
migration
ingestion
microbial killing

Pyrogen

Substance causing fever

monocytes and macrophages
granulocytes including neutrophils, eosinophils, and basophils
dendritic cells

Phagocytes include

Monocytes

Are small leukocytes that circulate in the blood ang mature into macrophages

Granulocytes

Are leukocytes that contain densely staining granules

Neutrophils

Have a short half-life and are important phagocytic cells that destroy pathogens within intracellular vesicles

Eosinophils and basophils

Are less abundant and store granules containing enzymes and toxic proteins that can be released upon activation of the cells.

Dendritic cells

Are also phagocytic and can degrade pathogens

Phagocytosis

Is a multistep process whereby a phagocytic cell, like a neutrophil, recognizes the pathogen, ingests it and then destroys the engulfed organism.

Phagosome

The neutrophil recognizes, engulfs, and internalizes the pathogen into an endocytic vesicle

Natural killer (NK)

Are large, granular lymphocytes morphologically related to T cells

10-15%

Natural killers makes up to how many blood leukocytes

Lectin-like NK cells receptors
Killer immunoglobulin-like receptors (KIRs)

NK cells express two types of surface receptors

Antibody-dependent cellular cytotoxicity (ADCC)

When antibody production is initiated in the adaptive immune response, NK cells play a critical role in ____________________________.

Innate lymphoid cells (ILCs)

Are a recently described group of innate immune cells that play a key role in regulating tissue immunity.

Cytokines

May include inflammatory and anti-inflammatory cytokines, chemokines, adhesion molecules and growth factors.

innate immunity

non-specific and no memory

Adaptive immunity

Specific and has memory

Chemotaxis

Is stimulated by proteins in the inflammatory exudate, including some chemokines

Fever

Is another common systemic manifestation of the inflammatory response and is a cardinal symptom of infectious disease

thermoregulator center

The regulator of body temperature is the _______________________________ in the hypothalamus.

interferon

Interferes viral infection

B cells and T cells

Develop into two main lymphocyte populations

Rapid, immediate response

Innate characteristics

Slow response

Adaptive characteristics

Innate

No memory, not long-lasting protection

Adaptive

Induces memory, responds rapidly and vigorously to second antigen exposure

Phagocytes, NK cells, innate lymphoid cells

Cells of Innate

T-lymphocytes-cell mediated,

B lymphocytes-antibody mediated, APCs

Cells of adaptive immunity

Complement defensins, cytokines, sensors (TLR, NOD-like receptors, RAG-1)

Mediators of Innate Immunity

Secreted molecules (cytokines, chemokines, complement)

Mediators of Adaptive Immunity

T-cells

Are lymphocytes that are produced in the bone marrow but travel to the thymus to mature

Antibody-mediated

CD4 T lymphocytes recognize the pathogen's antigen's bound to the class II MHC

Cell-mediated

Antigen-NHC class II complex is recognized by the CD4 T lymphocyte

CD4 T

Cells that develop stimulate B cells to produce antibodies and promote delayed hypersensitivity

CD8

cells direct their activity mainly at the destruction of cells in the tissue grafts, tumor cells, or virus-infected cells

Chemotaxis

Chemical signals attracts phagocytes to microorganisms

Adherence

Attachment of Phagocyte to surface of Microorganisms

Ingestion

Microorganism is engulfed by the phagolysosome

Digestion

Microorganism is digested inside the phagolysosome

Chemotaxis, adherence, ingestion, and digestion

Phases of phagocytosis

True

(True or false)

Chemotaxis allows phagocytes to migrate to infection sites and destroy invading bacteria

False

Phagocytes are the first line of defense.

Phagocytosis is an important first line of immune defense.

(True or false)

True

Phagocytes can also stimulate T and B cells

(True or false)

True

Toll-like receptors (TLRs) are a focus of current immunological research

(True or false)

pain, heat, redness, swelling, loss of function

5 cardinal signs of inflammation

IL-1
IL-6
TNF-a
IFNs

Proinflammatory cytokines that are commonly seen in infectious diseases.

IL-10
IL-11
TGF-b
IFN-b

Anti-inflammatory cytokines

Interferon

Part of innate immunity
Interferes viral synthesis
Example of cytokines

Interleukin

Leukocytes

Serve as communication or communicator among leukocytes

Chemokines

Originated from the word chemotaxis

These are cytokines that can also migrates/move.

chemotaxis

Chemical attraction of a phagocytic cell towards the MO

Cytokines

Can serve as biomarkers of disease and provide clues for mechanisms of disease

Antigen

can trigger or activate our immune system

Nonself antigen

A type of antigen that can trigger an immune response

Self antigen

The immune system can recognize that this antigen is not foreign

Large complex proteins

Which size triggers an immune response

Heteropolymer

Which type of antigen triggers an immune response

activated

In order for the B cell to produce antibodies they must be ______________

The activation happen with the help of a T cell

T-cell dependent

Even there's no T-cell the cell will be activated

T-cell independent

MHC II

Displayed on the surface B-cell through _______________

Polysaccharides and LPS

These thymus T-cell independent antigens induce B-cell responses with limited class switching and DO NOT induce memory

2 light chains

2 heavy chains

4 polypeptide chains they differ on molecular masses

Variable region

constant region

2 regions in antibody

Variable region (Amino terminal groups)

The specific part of the antibody that binds to the antigen

Fab and FC fragments

2 fragments of the body

Y shaped

Shape of the antibody

Immunoglobulin

Another term for antibodies

G A M E D

5 classes of Immunoglobulin

4 polypeptide chains

how many polypeptide chains in an antibody?

IgG

Major immunoglobulin

IgG1-4

4 classes of IgG

IgG

Only antibody that can cross the placenta providing protection to the fetus
Mediates Opsonization
Lasts 21 days (Long lived)

IgM

First to response
Largest antibody (Macro size)
Most efficient antibody, highest binding capacity.
Short-lived
Lasts 7 days (short lived)

IgA

Low serum concentration, found in tears, saliva, breast milk (colostrum)

IgE

binds to mast cells, basophils, eosinophils

for Elergic reaction

IgD

found in the matured B-cells

major surface antibody

Memory response or anamnestic response

Other term for secondary response

Agglutination and opsonization

Two mechanisms that enhanced phagocytosis

IgM

Most efficient during agglutination