Parasitology iClicker BA
Lab- Taelor taase001@fiu.edu Office hours by appmnt.
Medical Parasitology by Garcia
08/20/18
Parasitology: Study of the most common mode of life on earth, centered on animal parasites of humans, domestic animals & wild life
Parasite: An organism that lives in or on another organism (host) and either harms the host and/or lives at the expense of the host.
Why is parasitology important?
Parasite resistance
Insecticide resistance
Increased mobility (popularity in tropics a and subtropics)
Migration of refugees from war-ton areas
Military service personnel coming home from aboard
Modifications of the environment
Climate change (disease spread from tropics to more temperate regions)
Immunosuppression becoming more widespread:
- AIDS, cancer chemotherapy, and organ transplantation
- Indiscriminate release of toxic chemicals and carcinogens into environment.
08/22/18
Humans have acquired about 300 species of helminth
Parasitic fungus Ophiocordyceps unilateralis with stalk
worms and over 70 species of protozoa.
protruding from ant’s head. (fungus parasite, kingdom fungi)
Pocketbook mussel- Lampsilis ovata molluscan parasite, attracts bigger fishes and squirts out the larva to them.
Lampsilis fasciola: wavy-rayed lampmussel.
Tongue-eating isopod (Cymothoa exigua): is a parasitic isopod of the family Cymothoidae. This parasite enters fish through the gills,
and then attaches itself to the fish's tongue. The female attaches to the tongue and the male attaches on the gill arches beneath and
behind the female.
Common Vampire Bat (Desmodus rotundus): They have an anesthetic on their spit and an anticoagulant that allows the blood to keep
flowing and the host doesn’t feel anything. They have heat sensors near its nose that allow them to feel where the warm blood is
flowing closer to the skin.
Cuscuta sp. (dodder vine) use haustoria to obtain host’s nutrients. Parasitic plant
Common Cuckoo (Cuculus canorus) raised by Reed Warbler (Acrocephalus sp.)
The cuckoo bird looks for host nests.
Candiru or toothpick fish (Vandellia cirrhosa)
Pelophylax lessonae- The small frog, most commonly found in stagnant waters.
Pelophylax ridibunda- The bigger frog, most commonly found in more rapid flowing waters.
When these two mates, the hybrid is able to survive well in both environments, however, the genes of the Pelophylax lessonae are
turned off, so when the hybrid mates with another, the main genes that are inherited are those from the Pelophylax ridibunda, called
Hybridogenesis.
08/24/18
Brood parasitism: Brood parasites are organisms that rely on others to raise their young. The strategy appears among birds, insects and
some fish. Common Cuckoo
Symbiosis: Interaction among organisms in which one organism lives with, in, or on the body of another.
Symbionts: organisms involved in symbiotic relationships with other organisms, the host.
Basic Organismal Interactions
Neutralism: A lack of benefit or detriment experienced by either member of the pair of interacting organisms.
-
It describes interactions where the fitness of one species has absolutely no effect whatsoever on that of the other. Theoretical.
-
Zeros are used as a symbol. (0,0)
Competition: Some degree of overlap in ecological niches of two populations in the same community, such that both depend on the
same food source, shelter, or other resources, and negatively affect each other’s survival. Both are negatively affected. Unless the
competition ends, one species clears the anther one out and there is no more competition.
-
Ex. Carnivorous animals compete for prey. (Cape Buffalo, Battle at Kruger) (- , -)
-
Ex. Plants compete for sunlight, water, nutrients, pollinators, and dispersers of fruits and seeds.
-
Ex. The aquatic bladderwort (carnivorous water plant) plant (Utricularia) compete with tiny fishes for small crustaceans and
insects, and arthropods.
Phoresis: form of symbiosis when the symbiont (phoront) is mechanically carried about by its host; neither is physiologically
dependent on the other. – means to carry. Mechanically transfer from point A to B, no one benefiting or being harmed.
-
Ex. Bacteria on legs of a fly.
-
Ex. Fungal spores on feet of a beetle.
-
Ex. Aquatic snail eggs laid on birds’ feet.
-
Ex. Dermatobia hominis (human botfly)
-
Ex. Female botfly deposits egg on surface of mosquito.
Commensalism: One benefits and the other one is neither helped or harmed.
Protocooperation: A mutually beneficial symbiosis between organisms in which the interaction is not physiologically necessary to the
survival of either. (+ ,+)
-
Ex. Egyptian plover eats residuals from crocodile teeth.
-
Ex. Cattle egret removes ectoparasite from the back of the bovines.
-
Ex. Hermit crab inside shell over which sea anemones live.
-
Ex. Ants and aphids: Aphids are plant bugs that suck sugars out of the
Mutualism: Type of symbiosis in which both host and symbiont benefit from association. Usually obligatory, in most cases there is
physiological dependence.
-
Ex. Termites and intestinal protozoan fauna.
-
Ex. Blood-sucking leaches and intestinal bacteria.
-
Ex. Wuchereria bancrofti and Onchocerca volvulus infected with Wolbachia.
-
Ex. Cleaning symbiosis: cleaner wrasse (Labroides dimidiatus)
-
Ex. Lichen: Microscopic green algae or cyanobacteria and filamentous fungi.
-
Ex. Mycorrhizae (fungus-root)
-
Ex. Nitrogen fixation, the bacteria Rhizobium spp.
-
Ex. Cotesia congregate (parasitoid wasp) & C. congregate bravirus (CcBV)
08/27/18
Basic Organismal Interactions
Commensalism: A kind of symbiosis in which the symbiont (a commensal) benefits, and the host is neither harmed nor helped by the
association. (+,0) or (0, +)
-
Means “eating at the same table”.
-
Ex. Pilot fish and remoras.
-
Ex. Entamoeba gingivalis.
-
Ex. Barnacle on a whale.
-
Ex. Epiphytes on a tree: Epiphytes get sun exposure since they’re up in the canopy.
Amensalism: Asymmetrical interaction in which one organism causes a negative effect on another without being positively or
negatively affected in return.
-
Ex. Bread mold Penicillium that produces penicillin, an antibiotic that kills bacteria.
-
Ex. Black Walnut tree (Juglans nigra) produces juglone, an organic compound that is toxic or growth-stunting to many types
of plants.
-
Ex. Elephant walking in the forest, it’s neither harmed or benefit, but anything that falls under its feet gets harmed or killed. *
Predation: Animal interaction in which a predator kills its prey outright, it does not subsist on the prey while the prey is alive.
Parasitism: A symbiosis in which a symbiont benefits from the association, while it harms the host in some ways or lives at the
expenses of it.
-
Ex. Human infected with Guinea worm (Dracunculus medinensis)
THE PREDATOR AND THE PARASITE LIVE AT THE EXPENSE OF THE HOST OR PREY; INTERACTION OCCURS ONLY IF THERE’S AN ENCOUNTER.
Predator
Parasite
Kills its prey.
Normally does not kill its host.
Is large relative to the prey.
Is small relative to the size of the host.
Has numerous preys.
Has only one host (or one host at each stage in its life cycle)
Is not symbiotic.
Is symbiotic.
No post-encounter interaction.
Post-encounter interactions are where the real action begins!
How to Describe Parasites
Macroparasites: Large parasite that does not multiply in the host of interest.
-
Do not induce lasting immunity (exceptions)
-
Have more stable populations and causes endemic diseases.
-
Ex. Helminthes, arthropods, and other metazoans.
Microparasites: Small (or very small) parasite that multiplies within the host of interest.
-
Induce a lasting immunity.
-
Have unstable populations and cause epidemic diseases.
-
Ex. Fungi, protists, bacteria and virus.
Ectoparasite: Parasite that lives on the outer surface of its host.
-
Ex. Lamprey
Endoparasite: A parasite that lives inside its host.
-
Ex. Nematodes.
Obligate parasites: They cannot complete their life cycle without spending at least part of the time in a parasitic relationship. (most
parasites)
Facultative parasites: Not normally parasitic but can become so when they are incidentally eaten or enter a wound or other body
orifice.
-
Ex. Naegleria fowleri
-
Ex. Micronema deletrix
08/29/18
How to Describe Parasites
Accidental (incidental) parasite: A parasite found in other than its normal host.
-
Puts host and parasite into environment conditions to which neither is well adapted.
-
Ex. Toxocara canis in humans (visceral larval migrans)
Permanent parasite: A parasite that lives its entire adult life within or on a host.
-
Ex. Trichinella spiralis never sees the light of day
Temporary (intermittent) parasite or micropredators: A parasite that contacts its host only to feed and then leaves.
-
Ex. Mosquito, bed bug, flea, etc.
-
Ex. Vampire bat.
Parasitoid: Organism that is a typical parasite early in its development but finally kills its host during or at the competition of its early
development.
-
Often used in reference to many insect parasites of other insects.
-
Approximately 10% of described insect species are parasitoid.
-
Ex. Pseudacteon phorid
Hyperparasitism: condition in which an organism is a parasite on another parasite
-
Ex. Plasmodium spp. In Anopheles mosquitoes.
-
Ex. Tapeworm juvenile on flea.
Coelozoic: A parasite living in the lumen of a hollow organ.
-
Ex. Stomach,
Histozoic: A parasite living within the tissues of a host. (-Ex. Liver)
How to Describe Hosts
Vector: Any agent, such as water, wind, or insect (host), That transmits a disease organism.
Definitive host: Host in which a parasite achieves sexual maturity, if there is no sexual reproduction in the life of the parasite, the host
most important to humans is the definitive host.
Intermediate host: Host in which a parasite develops to some extent but not to sexual maturity.
Paratenic (transport) host: Host in which a parasite survives without undergoing further development.
Reservoir host: Host that serves as a means of sustaining a parasite when it is not infecting humans, which is typically another suitable
definitive host.
Life cycle of a giant kidney worm (Dioctophyme renale)
How to Describe Life Cycles
Urban (domestic) cycle: Normal to the human environment, involves domesticated animals.
Sylvatic cycle: Existing normally in the wild, involves wildlife.
08/31/18
Selection: A composite of all the forces that causes differential survival and differential reproduction among genetic variants (artificial
selection vs. natural selection); a key mechanism of evolution.
-
Ex. Reciprocal selection pressures exists between parasites and their hosts. (hosts select for the best parasites and parasites
select for the best host)- the best is the greatest fitness.
Mutation is the raw material by which selection works off of.
-
Ex. Artic fox and Artic hare.
Host-Parasite Coevolution
Evolution: Genetic changes in populations of organisms through time that lead to differences among them.
-
Evolution only occurs when there is a change in gene frequency within a population over time.
-
There genetic differences are heritable and can be passed on to the next generation.
It’s in the best interest of the parasite to possess adaptations that allow it:
-
To encounter the host.
-
Parasites that possess genetically inheritable behavioral traits that
It is on the best interest of the host to possess adaptations that allow it:
-
To avoid encountering the parasite
-
To get rid of the parasite if an encounter takes place
Red Queen hypothesis: Originally proposed by Leigh Van Valen (1973)
-
Metaphor of Alice and the Red Queen from Lewis Carroll’s, Through the Looking Glass
-
Species have to run (evolve) in order to stay in the same place (extant)
-
Cessation of change may result in extinction
Ex. Parasite-Host Coevolution
-
Each time the parasite population acquires a new “weapon” (Ex. New antigen), the host population is led to produce a new
defense (new antibody, directed at this antigen)
-
Parasite and host populations are engaged in an “endless” arms race/war. Only ends when one of the species goes extinct.
09/05/18
Adaptations for Parasite Transmission
A. Reproductive: produce more eggs and sperm than their free-living relatives do.
-
High reproductive potential
-
Asexual reproduction
-
Hermaphroditism
-
Self-fertilization
B. Behavioral
1.
Adaptive advantage of parasite behavior.
-
Ex. Schistosoma mansoni cercariae
2.
Parasite may alter host behavior
-
Ex. Dicrocoelium species
𝐶𝑜𝑤 ⟶ 𝑆𝑛𝑎𝑖𝑙 → 𝐴𝑛𝑡 → 𝐶𝑜𝑤
C. Morphological adaptations
-
Size, many parasites are larger than their free-living relatives
-
Attachment organs-suckers, hooks & spines, penetration organs, and cysts
-
Loss (regression_ of anatomical structure, organs of sense, locomotion, digestion, etc.
D. Biochemical adaptations
-
Energy metabolism-catabolic pathways are usually reduced or modified in many parasites.
-
Nutrient uptake: There’s an elaboration of transport mechanics
-
Synthetic reactions: synthetic capacities are reduced when compared with their free living,
E. Immunological adaptations
F.
Life Cycle Adaptations
09/07/18
How to Identify a Species?
Binomial nomenclature: A system in which a species is given a compound name.
-
Carlos Linnaeus (1707-1778), father of modern taxonomy.
-
1st word is the genus in which the species is placed (1st letter capitalized).
-
2nd word is the species epithet, (uncapitalized) used to separate the species from other members of the same genus.
-
Names of genera and lower taxa are always italicized.
Taxa: Are groups, ranging from species, to the increasingly inclusive genera, families, orders, classes, phyla, kingdoms and domains.
Hierarchical System of Classification
Taxonomy: Study of basic classification, ordering and naming organisms.
-
Basic subdiscipline of Biology.
-
Scientific name carries with it massive amounts of information:
a.
Describes the organism in detail: Utilizes morphological and molecular characters.
b.
Provides scientific names for new species.
c.
Preserves collections: Permanent slides and voucher specimens.
d.
Classification of the organism, keys for their identification, and on their distributions.
e.
Investigates their evolutionary histories.
f.
Considers their environmental adaptations.
Systematics: Study of classifications & biological diversity, with an evolutionary context.
a.
Seeks to understand the origin of diversity at all levels of classification: Utilizes morphological and molecular
characters).
b.
Provides scientific names for new species.
c.
Preserves collections: Permanent slides and voucher specimens.
d.
Classification of the organism, keys for their identification, and on their distributions.
e.
Investigates their evolutionary histories.
f.
Considers their environmental adaptations.
Investigating the evolutionary history of a taxon is not easy because history:
-
Is not something we can see.
-
Only happens once.
-
Only leaves behind clues.
Systematics use clues to try to reconstruct evolutionary history to research the pattern of events that have led to the distribution and
diversity of life.
Phylogenetic systematics (cladistics): Is a methodology used by systematists to infer (hypothesize) a species’ evolutionary history
(phylogeny).
-
Pioneered by Will Henning (1913-1976)
-
Used in the discovery of monophyletic groups (evolutionarily real entities).
-
This method exclusively relies on shared derived character states (homology).
There are 3 basic assumptions in cladistics:
1.
Change in characteristics occurs in lineages or groups over time.
-
Only when characteristics change are we able to recognize different lineages.
2.
Any group of organisms are related y descent from a common ancestor.
-
Supported by many lines of evidence:
-
Ex. Same genetic code (DNA), biochemical pathways (glycolysis), etc.
3.
There is a bifurcation or branching pattern of cladogenesis.
-
When a lineage splits, it divides into two exactly groups.
Phylogeny: Evolutionary hypothesis of the origin and diversification of a taxon.
-
Treelike diagram.
-
Relationships between taxa are shown in the branching patterns.
-
Characters among the taxa used to produce phylogenies include: Anatomical, behavioral, physiological, or molecular
attributes.
Clade: A group of organisms that includes an ancestor and all of its descendants.
Ingroup: A taxon of interest.
Outgroup: A related taxon chosen for the purpose of comparison.
Node: Internal branch point that represents the common ancestor of those descendants; a speciation event.
Sister group: Two descendants that split from the same node.
Each colored rectangle represents a clade:
How to Describe Characters?
Homologous character: A character present in two taxa because their common ancestor had that character.
Analogous character: A similar character that has the same function but different evolutionary origin.
Homoplasy: Is similar NOT due to homology but resulting from convergence, parallelism or reversal.
Plesiomorphic: Ancestral characters: Present in both the ingroup and the outgroup.
-
Uninformative character.
Autapomorphic: Derived character: Evolutionary novelty; present only in one taxon of the ingroup.
-
Uninformative character.
Synapomorphies: Shared derived characters that set a taxon apart from related taxa and their most recent common ancestor.
-
Informative character.
How to Describe Groups?
Monophyletic: A group of taxa that includes a hypothetical ancestral taxon and all its descendants.
-
Defined by a suite of shared-derived characters (synapomorphies).
-
Ex. Mammals.
Paraphyletic: A group of taxa that includes a hypothetical ancestor but does not include all of the ancestor’s descendants.
-
Defined by a suite of ancestral trials (plesiomorphies) which have been modified or lost in the excluded species,
-
Ex. Class Reptilia is paraphyletic by not including birds.
Polyphyletic: A group of taxa that do not share a most recent common ancestor.
-
Defined by convergent traits (homoplasies).
-
Ex. Wings of birds, bats and butterflies.
09/10/18
Immune System: A functional system whose components attack foreign substances or prevent their entry into the body.
Immunity: State in which a host is more or less resistant to an infective agent.
-
Used in reference to resistance arising from tissues that are capable of recognizing and protecting the animal against nonself
invaders.
Passive immunity: That you get without your system having to work for it, antibodies, getting help from an external source.
Active immunity: Your body doing the work, generating immune response.
Innate immunity: A mechanism of defense that does not depend in prior exposure to the invader.
Adaptive (acquired) immunity: A mechanism of defense that is specific (targets an epitope) to the particular nonself material, requires
time for development, and occurs more quickly and vigorously on secondary response.
Three different lines of defense: The first two fall into innate and the third into adaptive or acquired.
09/12/18
I. Nonspecific Immunity (Innate immunity)
The first line of defense: Skin and Mucous Membranes
1.
Skin (integumentary system): As an effective barrier against pathogens.
A. Oil & sweat glands give skin surface a pH of 4-5.5.
B. Sweat contains lysozyme (digests bacteria cell wall).
C. Normal flora includes non-pathogenic bacteria & fungi.
D. Epidermis 10-30 cells thick, dermis 15-40 times thicker.
2.
Mucosal Surfaces: As an effective barrier against pathogens.
A. Digestive tract.
a.
Saliva contains lysozyme (also in tears).
b.
Acidic environment of stomach, pH of 1.5-3.5 (concentrated HCL solution).
c.
Digestive enzymes in intestines.
d.
Nonpathogenic normal flora.
e.
Vomiting & diarrhea may expel pathogens.
B. Respiratory tract.
a.
Pathogens trapped by mucus in bronchi and bronchioles.
b.
Ciliated epithelial cells sweep mucus toward the glottis.
c.
Coughing and sneezing expels pathogens.
C. Urogenital tract.
a.
Vaginal secretions viscous and acid.
b.
Secretions promote growth of normal flora.
c.
Acidic urine of both sexes may wash out pathogens.
What aspect of the castle analogy would best represent the first line of defense?
A.
B.
C.
D.
E.
Elevator
Archers
MMA Soldiers
Castle wall
All of the above
II. Nonspecific Immunity (Innate immunity):
The Second Line of Defense
Phagocytes, inflammation, complement & interferon, cytokines & chemical signals, and antimicrobial proteins.
-
Recognizes a wild spectrum of pathogens without a need for prior exposure.
-
Key players include neutrophils, monocytes, and macrophages.
-
These cells phagocytose pathogens and trigger the cytokine and chemokine network.
-
Can lead to inflammation and specific immune response.
Agranulocytes (mononuclear leukocytes)
1.
Macrophages.
a.
Monocytes mature into active macrophages at site of infection.
b.
Intracellular killing and digest pathogens via phagocytosis.
c.
Phagosome fuses with lysosome (oxygen-containing and nitrogen-containing free radicals)
d.
Roam continuously in the extracellular fluid bathing tissue.
e.
Antigen-presenting cell (APC) for helper T cells (TH).
f.
Respiratory burst for additional cell-killing ability (liberates deluge of free radicals).
g.
Express Fc receptor molecules for IgG to trap antigen-antibody complexes.
Ex. Kupffer cells of liver, dendritic cells in blood, microglial cells in CNS, etc.
Granulocytes (polymorphonuclear leukocytes)
1.
Neutrophils.
a.
Most abundant circulation leukocytes (50%-70% of peripheral blood leukocytes).
b.
First cell on site of tissue damage or infection.
c.
Intracellular killing via phagocytosis, greater range of reactive oxygen radicals.
d.
Large numbers in blood until attracted to tissues during inflammation.
e.
Roam in the extracellular fluid bathing tissue.
f.
Express Fc receptor molecules for IgE.
2.
3.
Eosinophils.
a.
2%-5% of the total leukocytes in blood.
b.
Important in the elimination of parasites.
c.
Degranulation, next to parasite, releases extremely potent mediators (enzymes & toxins).
d.
High blood count is often associated with parasitic infection & allergic diseases.
e.
Express Fc receptor molecules for IgE.
a.
Circulating cells, least numerous at about 0.5%.
b.
Not important as phagocytes.
c.
Release mediators such as histamine to promote inflammation.
d.
Express Fc receptor molecules for IgE.
Basophils.
09/14/18
Mast cells:
1.
Primarily located under mucosal surfaces.
2.
Release chemical mediators such as histamine to promote inflammation.
3.
Triggered during allergic responses.
4.
Express Fc receptor molecules for IgE.
5.
Important component of the inflammatory response.
The Second Line of defense
Acute inflammation: Occurs over seconds, minutes, hours and days.
-
Chemical signals are released by infected or injured cells during initial response to tissue damage (acute phase).
Ex. (histamine, prostaglandins, bradykinins).
1.
Dilation of local blood vessels increase blood flow at sites (red & warm).
2.
Increased permeability of capillaries causing edema (tissue swelling).
3.
Tissue swelling puts pressure on nerve endings (pain & potential loss of function).
4.
Macrophages and neutrophils release cytokines, interleukin-1 (IL-1) and tumor necrosis factor (TNF) which acts on
hypothalamus to raise body temp. (fever).
5.
a.
Fever is one of the most common symptoms of infection.
b.
Fever simulates phagocytosis and causes liver and spleen to store iron and zinc needed by bacteria.
c.
Fever may destabilize certain viruses and bacteria.
Cell death (necrosis) always occurs to some degree during inflammation.
Delayed type hypersensitivity (DTH): A type of cell-mediated immunity in which the ultimate effectors are activated macrophages.
-
A period of 24 hours or more elapses between the time of antigen introduction and the response to it in an immunized
subject.
-
Delayed occurs because TH1 cells with receptors for that particular antigen require time to arrive at antigen site, recognize
the epitopes on APCs, and become activated and secrete IL-2, TNF, and IFN-y.
Ex. Poison ivy plant with urushiol
Ex. Tuberculin skin test (montoux) reaction.
Immediate hypersensitivity: A type of antibody-mediated immunity which involves degranulation of basophils and mast cells in the
area.
A. Basophils and mast cells have receptors that bind the Fc portions of antibody (IgE).
B. When exposed to the same allergen a 2nd time, degranulation occurs.
C. Results in dilation of local blood vessels and increased permeability, edema.
D. Immediate hypersensitivity is important in some parasitic infections.
E. Immediate hypersensitivity in humans is the basis of allergies and asthma.
Anaphylaxis: (Systemic immediate hypersensitivity): Hypersensitivity produces by exposure to further doses of the same protein,
usually when exposure is within less than two weeks.
Ex. Bee stings.
-
Basophils and mast cells release pharmacologically active substances
-
Widespread rapid inflammatory response that may be fatal if not treaded rapidly
-
Tremendous drop in blood pressure.
-
Swelling of epiglottis can block trachea, and bronchial construction.
Chronic inflammation: Acute inflammation that fails to heal, occurs over a long time and is disease related.
Fibrosis: Arises from abnormal and continuous wound repair processes that fail to terminate resulting in elevated levels of collagen
and scarring.
Granulomas: Nodules of inflammatory tissue that may accumulate around persistent antigen.
Abscess: When necrotic debris confined to a localized area forms pus that may cause an increase in hydrostatic pressure.
Ulcers: An area of inflammation that opens out to a skin or mucous surface.
See examples on page 15.
09/17/18
Complement and Interferons
A. Complement.
1.
Consists of approximately 30 diff. proteins.
2.
Circulate freely in blood plasma, generally in inactive form
(zymogen)
3.
Complement can be activated y classic pathway (antigenantibody complex) or alternative pathway (spontaneously) or
lectin pathway (cell wall polysaccharides of certain bacteria
and fungi)
4.
Complement proteins (C3b) coat the pathogen surface
(opsonization), thus promoting phagocytosis and destruction of
the pathogen by macrophages and neutrophils, which have
receptors for C3b.
5.
C5a is an important chemotactic protein, helping recruit
inflammatory cells.
6.
Complement C5b initiates pathway for membranes attack
complex (MAC) that form pores in pathogens that have lipid
membrane to induce lysis.
B. Interferons (IFN-a, IFN-B, IFN-Y)
1.
A class of proteins synthesized upon a parasitic infection of a cell.
2.
Act as messenger to protect normal cells in vicinity from becoming infected.
3.
IFN—a and IFN-B induce the degradation of RNA and block protein production.
4.
IFN-Y is produced by TH cells and natural killer cells to stimulate cells in the cellular response.
Cytokines and Cell signaling
A. Cytokines
1.
Cytokines are protein hormones utilized by immune cells to communicate.
2.
Can affect same cells that produced them, cells nearby or cells distant in body.
Ex- Interferon, interleukin, growth factors, etc.
B. Cell Signaling
1.
Ligand binds to a specific cell receptor protein, initiating intracellular signal cascades.
2.
Ligands may be located on cell surfaces of neighborhood cells, dissolved in blood (cytokines) or on the surface of
secreted by pathogens.
3.
Cascades may activate transcription factors or proteins that control gene induction, phagocytosis, apoptosis, or secretion.
Ex- JAK-STAT pathway: 3 main components include:
1.
Receptor
2.
Janus Kinase (JAK)
3.
Signal Transduce and Activator of Transcription (STAT)
1.
Transmembrane receptor activated by cytokine.
2.
Activates the JAK protein, which adds phosphate groups (P) to the
receptor.
3.
o
Kinases: Proteins that add phosphate groups to other proteins.
o
Phosphate groups: Act as “on” & “off” switches on proteins.
STAT is recruited and itself becomes phosphorylated, forms dimer,
and moves into the cell nucleus, where it binds to DNA promoter
region.
Pattern Recognition Receptors: Receptors with broad specificity that bind to molecules on the surface of pathogens, stimulated by
PAMPs.
-
Pathogen-associated molecular patterns (PAMPs): Small molecular motifs conserved within a class of pathogens.
A. Scavenger receptors: Bind lipoproteins and lipopolysaccharides from bacterial cells including Gram-positive bacteria
(lipoteichoic acid) and Gram-negative bacteria (lipopolysaccharide).
B. Complement receptors: Integral membrane proteins that recognize fragments of complement and mediate various defense
functions, including phagocytosis.
C. Toll-like receptors (TLRs): Single, membrane-spanning, receptors that recognize structurally conserved molecules of
carbohydrates, nucleotides, and proteins derived from viruses, bacteria, protozoa and helminthes parasites.
III. Specific Immunity (Adaptive immunity):
The Third Line of Defense
Four important aspects of immune response:
1.
Nonself recognition: Ability to distinguish self-antigens from nonself.
2.
Antigen-Specific: recognizes and is directed against specific antigens.
3.
Systemic Response: Immunity is not restricted to initial infection site.
4.
“Memory”: Recognizes and mounts stronger attack on previously encountered pathogens.
Schistosoma infection resulting in
Granuloma forms to encapsulate
Liver fibrosis.
Persistent antigens.
Leishmaniasis and skin ulcer
Dracunculus infection
abscess