MicroBio Midterm 4

Pattern Recognition Receptors (PRRs)

proteins on or in cells that recognize specific compounds unique to microbes or tissue damage, allowing the cells to sense the presence of invading microbes or damage

Toll-like receptors (TLRs)

transmembrane protein of immune cells that recognizes pathogens and activates an immune response directed against those pathogens

Pathogen-associated molecular patterns (PAMPs)

Molecules associated with groups of pathogens that are recognized by cells of the innate immune system.

Cytokines

Proteins that regulate the intensity and duration of immune response

Physical barriers to infection

skin, mucous membranes, ciliary escalator, lacrimal apparatus, saliva, urine, vaginal secretions, earwax

Chemical barriers to infection

acidic pH, lysozyme, saliva, gastric juices, urine, vaginal secretions

Normal Microbiota line of defense

Competitive exclusion, produce substances, building an immune system, probiotics, probiotics

Lymphatic system

Structures and organs containing lymph tissues, containing large numbers of lymphocytes (T and B cells), filers that trap microbes, macrophages and dendritic cells

Neutrophils (PNMs)

Highly phagocytic, Motile, active in initial stages, can leave blood and enter infected tissues, destroyer of microbes and foreign particles

Basophils

Release histamines, important for inflammation

Eosinophils

Somewhat phagocytic, can leave blood, can discharge peroxide ion, kills certain parasites

Natural Killer (NK) cells

Destroys targets by cytolysis and apoptosis. Toxic substances released from lytic granules, blood spleen, lymph nodes, red bone marrow, cause pores, recognizes reduced number of MHC-I molecules

T cells

Cell-mediated immunity

B cells

Produce antibodies, carries immunoglobulin on surface, host are IgM and IgD - all recognize same epitope

Macrophages

Phagocytosis; process and present antigens to lymphocytes for the immune response

Dendritic cells

Phagocytosis and initiate adaptive immune response

Monocytes

Not actively phagocytic until they leave the blood and mature into macrophages

phagocytosis

Ingestion of microorganisms or other substance by a cell

Fixed macrophages

Reside in particular tissues

Free macrophages

Roam and gather at sites of infection

Chemotaxis

Microbial products, components of damaged tissue and WBC, peptide

Adherence

PAMPs to receptors, causes phagocytes to release cytokines, uses opsonins to make recognition easier

Ingestion

Pseudopods surround microbe, meet and fuse creating a phagosome (phagocytic vesicle)

Digestion

Fusion of the phagosome with a lysosome to create and phagolysosome, undigested material is discharged

Inflammation

Damage caused by microbes, physical, or chemical agents - trigger a local defense mechanism (pain, redness, immobility, swelling, heat)

Acute inflammation

Rapidly develop, last short period of time, mild self-limiting, neutrophils principal mechanism

Chronic inflammation

Slower developing, longer lasting period, severe and progressive, monocytes develop into macrophages

Histamines

vasodilation and increased permeability of
blood vessels

Kinins

vasodilation and increased permeability;
chemotaxis of neutrophils

Prostaglandins

intensifies histamines and kinin
response; helps phagocytes move through capillary
walls; associated with pain

Leukotrienes

increased permeability; help phagocytes
attach to pathogen

Cytokines

produced by fixed macrophages; vasodilation and increased permeability of blood vessels, chemotaxis of phagocytes and adaptive immune cells

margination

blood flow decreases and Neutrophils and Monocytes
migrate to area and stick to the lining of blood vessels

diapedesis

Phagocytes squeeze through blood vessel cells

Fever

systemic (whole body) response of abnormally high body temperature
Slows growth of bacteria
Speeds up body's reactions
Speeds of antiviral interferons
Decreases iron available to microbes
Help increase T cell production

Complement protein activation

Complement proteins are inactive until split into fragments - cascade reactions

Classical activation

antibodies attach to antigens - Antibody-antigen complexes activate cascade

Alternative activation

C3 combines with complement proteins factors
B, D and P (Properdin) at the microbes surface

Lectin activation

Cytokines stimulate liver to produce lectins (proteins that bind carbohydrates), enhance phagocytosis, create cascades

Interferons

cytokines produced by cells; have antiviral activity, play major role in acute viral infections

Siderophores

Bacteria produced, compete to gather iron by stealing it from other proteins by binding iron more tightly

Hemolysis

Lyses RBC, hemoglobin is degraded to get the Iron

Antimicrobial Peptides (AMP)

Short peptides of 15-20 amino acids, produced in response of protein and sugar molecules on microbes
Inhibits cell wall synthesis
Forms pores in plasma membrane (lysis)
Destroys DNA ands RNA
Broad spectrum
Synergistic with other AMPs

Lack of immunity

Susceptibility

Adaptive Immunity

Defenses that target a specific pathogen after exposure

Humoral Adaptive Immunity

B cells & Antibodies, fight extracellular invaders, B cells matured in red bone marrow, found in blood and lymphoid organs

Cellular Adaptive Immunity

T cells & Cell mediated immunity, TCRs, produce cytokines, precursors made in red bone marrow, mature T cells produced by Thymus, Fight antigens intracellularly

Where do stem cells develop into blood cells

Red bone marrow

Active Adaptive immunity

Immunity produced by the person infected, long lasting

Passive Adaptive immunity

Antibodies transferred from one person to another, transfer of antibiotics from mother to infant, lasts as long as antibodies are present (mostly a few weeks to months)

Artificially acquired active immunity

Exposure to antigens from vaccine, immune response with no infection

Artificially Acquired Passive immunity

Injections of antibodies, post exposure prophylaxis, short lived, delivers immediate immunity

Cytokines

Chemical messengers produced in response to a stimulus, communication between cells, soluble proteins or glycoproteins, produced by immune cells, react on cells that have receptors for them

Interleukins (ILs)

Cytokines communication between leukocytes

Chemokines

Induce migration of leukocytes to infection or tissue damage

Interferons (INFs)

Interfere with viral infections of host cells

Tumor necrosis factor alpha (TNF-a)

Involved in inflammation

Hematopoietic cytokines

Control stem cells that develop into red and white blood cells

Cytokine Storm

Production of cytokines causing more cells to produce cytokines (can do damage to tissues - flu, ebola)

Antigens

Typically a pathogen, substance that causes the production of antibodies, detection causes SPECIFIC antibody

Antibodies

Soluble proteins designed to recognize and bind to a specific antigen, have at least 2 identical antigen binding sites (to bind to specific epitope)

Epitopes

Part of the antigen molecule in which an antibody attaches itself

Antigenic determinants

The part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, and T cells

Hapten

Low molecular mass antigen that needs a carrier molecule

Humoral Adaptive Immunity

B cells, antibodies, Recognize and combat antigens, Fight extracellular, Found in blood and lymph rogans, ,matured in red blood cells

Cellular Adaptive Immunity

T cells, Cell mediated response, TCR, destroys cells and produces cytokines, T cells produced in Thymus, fights intracellularly

Valence

Number of antigen binding sites on an antibody

Variable regions

Part of the antibody that bind to antigen

IgG antibody

Monomer, 80% of total antibodies found, triggers complement system, bivalent, enhances phagocytosis, can cross placenta

IgM antibody

Pentamer, 6% of total antibodies, short lived, activates complement system, valency is 10

IgA antibody

Dimer with Secretory component, 13% of antibodies, most common in mucous membrane and bodily secretions, prevents attachment of pathogens, short lived

IgD antibody

Monomer, 0.02% of antibodies found, B-cell surface, blood, and lymphs, short lived, helps with immune response

IgE antibody

Monomer, 0.002% of antibodies, bound to mast cells and basophils, percentage increase with allergic reactions and parasites, short lived, bivalent

Immature lymphocytes

Lack fully developed antigen specific receptors

Naive lymphocytes

Have receptors but have not yet encountered "correct antigen"

Activated lymphocytes

Have bound antigen and received confirmation, are able to proliferate

Effector lymphocytes

Descendants of activated lymphocytes (Ex. plasma cells for B lymphocytes)

Memory lymphocytes

Long-lived descendants of activated lymphocytes; responsible for rapid secondary response if antigen is encountered again

Clonal deletion/Negative Selection

B cells are exposed to "self antigens" and undergo apoptosis and are killed is they bind - prevents autoimmune disease

B cell receptor (BCR)

anchored protein to surface of B cell, allows B cell to recognize its target epitope

T-dependent antigen

Antigen requires a T helper cell to activate B cell

T-independent antigen

B cell can be activated directly by the antigen, antigens provoke weaker immune response, no memory cells generated

Antigen-presenting cells (APCs)

present potential antigenic fragments to T cells, associated with cellular immunity

Major histocompatibility complex (MHC)

collection of glycoprotiens in the cells plasma membrane

Agglutination

Antibodies cause antigens to clump together

Opsonization

Coating of the antigen with antibodies, enhance phagocytosis

Neutralization

Coat bacteria, virus, or toxin - block adhesion and attachment to host

Activation of complement

Inflammation and lysis

Antibody-dependent cell mediated cytotoxicity

Antibodies attach to target cells, cause destruction by macrophages, eosinophils, and NK cells

Thymic selection

Immature T cells that recognize hosts and are eliminated

CD4+

T help cells, work with B cells mainly by cytokine signaling, bind to MHC II antigen, activation results in proliferation and secretion of cytokines

CD8+

Cytotoxic T lymphocytes, bind to MHC I antigen

Antigen Presenting Cells (APCs)

Have MHC on their surfaces, present potential antigenic fragments to T cells. Consist of B cells, Dendritic cells, Activated Macrophages, and possibly Neutrophils

Dendritic Cells - APC

Main APC, sentinel: engulf invaders, degrade and transfer them to lymph nodes to display to T cells

Activated Macrophages

Ingestion of antigenic material that can activate macrophages, more effective than phagocytosis

TH1 cytokines

activate macrophages, stimulate production of antibodies through activating B cells, activated Cytotoxic T lymphocytes

TH2 cytokines

Stimulate production of antibodies through activation of B cells, activation of eosinophils

TH17 cytokines

Recruit neutrophils to act on certain infections of extracellular bacteria and parasites

Treg

Combat autoimmune reactions by suppressing T cells that escaped Thymus deletion, protect resident microbiota

Perforin

Forms pores - useful in apoptosis