Foundations of Biology 2: Module 1 - Species Interaction & Immunology

Immunity

body’s ability to resist infection due to previous exposure, vaccination, or innate protection

Immunology

study of how immune system prevents/destroys foreign material

Innate Immune Response

• General response to any pathogen, nonspecific

• Initial line of defense and immediately activates

• Present at birth and does not change

• Include physical, mucousal, chemical, and microbial barriers in first line

• Include myeloid-derived cells and Natural Killer Cells, inflammation reaction, etc in second line

Adaptive Immune Response

• Specific and tailored

• Not present at birth but aquired throughout life

• Increase in strength and speed with each subsequent exposure

• Takes ~10 days to activate

Humoral Response

B cells encounters antigens in environment and binds via receptors on cell surface (same as antibodies when detached) which triggers B cell division into memory and daughter cells. Sometimes, after binding, B cells will require confirmation from helper T cells to initate the sequence.

Cell Mediated Response

T cells are presented with antigens from MHC proteins on cells and are activated when receptors bind. Activation results in proliferation of Th and Tc and results in cell death when Tc binds.

Primary Immune Organs

bone marrow and thymus where blood cells are synthesized/mature

Bone Marrow

Site of all immunological cell synthesis and maturation for B cells, basophils, neutrophils, and eosinophils

Thymus

Site of T cell maturation after initial synthesis

Secondary Immune Organs

where waste and toxins are filtered and screened for pathogens, include lymphoids in neck, liver, lymph nodes in gut, groin and arm, spleen , appendix, tonsils, adenoids

Hematopoetic Stem Cell

• Multipotential (pluripotent)

• Divides into 2 primary lineages myeloid+dendritic and lymphoid

Hematopoesis

The development of all RBC and WBC through pluripotent hematopoetic stem cell

Proliferate

One cell makes more copies of the same cell

Differentiate

One cell makes genetic changes to mature into new cell, cannot go back on what it commits to becoming

Myeloid Progenitor (Stem Cell)

• Develop into RBC, granulocytes, monocytes, platelets

• Lineage can mature within bone marrow

Lymphoid Progenitor (Stem Cell)

• Develop into lymphocites (T Cells, B Cells) and Natural Killer Cells

• Lineage requires maturation outside of bone marrow

Granulocyte

• Dump preformed toxic granules on invaders indiscriminantly

• Basophils, Eosinophils, Neutrophils, Mast Cells

Lymphocyte

• natural killer cells, B cells, T cells

• mostly in lymph nodes

Monocytes

• Innate immunity: phagocytosis and present antigens to helper T cells

• Develop into dendritic cells and phagocytes

• Produced in bone marrow, mature in blood and then can also travel to tissues

Dendritic Cell

• Communicate between innate and adaptive responses

• In blood when immature, then travels to lymph and tissues

• Phagocytosis and antigen presentation, but also activate T cells

Macrophage

• Mature in tissues and function in tissues and lymph nodes

• Phagocytosis and antigen presentation on cell surface

Basophils

• Made in bone marrow, found in blood

• Release histamines

• Some responsibility for allergies

Eosinophils

• Granulocyte

• Made in bone marrow, found in blood

• Kill antibody-coated parasites

• Responsible for allergies when attacking allergens instead of parasites

Neutrophils

• First to arrive at scene of injury for immediate signaling

• Phagocytes responsible for consuming pathogens, cause inflammation

Mast Cells

• Made in bone marrow, mature and function in tissues

• Already present at site of injury

• Release histamines to trigger inflammation and thus adaptive response

T Cell

• Adaptive Cell-Mediated Response

• Mature in thymus, travel to lymph

• Require presentation from MHC protein on cells to activate

• Receptors are 2 polypeptide chains with one binding site, but will not find antigens without presentation

• Either help confirm foreign pathogen to initate defense or kill cell baring specific antigen

• Can produce memory cells

B Cell

• Adaptive Humoral Response

• Mature in bone marrow, travel to lymph

• Recognize pathogens through receptors, then differentiate into plasma cells to produce antibodies

• Can produce both daughter and memory cells

Natural Killer Cell

• Mature in lymph nodes and found in tissues

• Lymphocyte but INNATE IMMUNITY

• Recognize when self-cell has become infected/cancerous and kills (lyse)

Helper T Cell

• Express CD4 which recognizes MHC II on presenting cells that have present either digested fragments or entire antigen (b cell)

• Present in both humoral and cell mediated response

• Can activate previously unexposed B cells or, if presented from B cell, can confirm and initiate B cell sequence through cytokine release

• Main role is chemical communication

Cytotoxic T Cell

• Express CD8 which recognizes MHC I proteins

• MHC I is present on all cells, but are targetted if abnormal or have viral proteins attached

• If recognized and bound, it pokes holes in the cell to trigger cell death

Inflammation

• Occurs in response to response to tissue damage

• Role is to contain site of damage, localize response, restore tissue function

• Mast cells release histamines (also tumor necrosis factors and prostaglandins) at site of injury which diffuses throughout

• Histamines make blood vessels “leaky” and dilated so that WBCs (neutrophils) can escape

• Causes redness, heat, pain, swelling

Phagocytes

• Monocytes, macrophages, dendritic cells, neutrophils, eosinophils (technically also B cells)

• Engulf particles and destroy,can also release cytokines to warn of infection

Cytokines

Small proteins that act as chemical messengers communicating in the immune system

Pathogen Associated Molecular Patterns (PAMPS)

• reoccurring molecular structures that all bacteria/viruses/pathogens have

• self body cells do not have them

Pathogen Recognition Receptors (PRR)

• present in all innate phagocytic cells

• specifically recognize PAMPS on pathogens.

• recognize pathogens in general rather than a specific pathogen.

Antigen

• toxic/ foreign substance not usually present in the body

• triggers immune response

Antibody

• can only bind and mark cells for death, does not kill

• may neutralize viruses by binding to proteins and preventing entrance

• cause opsonization and agglutination

• 2 heavy chains and 2 light chains, each with a variable and constant region

• variable region in between the heavy and light chains is antigen binding site

• constant region attracts PRRs to bind when exposed, which only occurs after antibodies bind

Opsonization

coats pathogen to attract phagocytes (ie sugar coat)

Agglutination

• clumps antigens together to make more visible to phagocytes

• possible because each b cell receptor and antibody have two identical antigen binding sites

Four Cardinal Signs of Inflammation

1. Pain

2. Swelling

3. Heat

4. Redness

Histamine

compound released by mast cells and phils that trigger inflammation and sometimes allergic reactions

Leukocyte

white blood cells

Erythrocyte

red blood cells

bone marrow

-phil maturation location

-phil cell primary function sites

blood

tissue

mast cell maturation location

tissue

mast cell primary function site

tissue

dendritic cell maturation location

tissue and lymph

dendritic cell primary function site

tissue

macrophage maturation location

tissue and lymph

macrophage primary function site

blood

monocyte maturation location

blood and lymph

monocyte primary function site

lymph node

natural killer cell maturation location

tissue

natural killer cell primary function site

bone marrow

b cell maturation location

lymph

b cell primary function location

t cell maturation location

thymus

lymph

t cell primary function location

Phagocytosis

Cell engulfs extracellular pathogen and breaks it down through phagosome combining with lysosome. In antigen presenting cells, digested pieces are stuck to MHC II protein

MHC class I

present on all nucleated cells (not RBC) and present self protein or endogenous antigen

MHC class II

only found on antigen presenting cells, present exogenous antigens exclusively to helper T cells

Epitope

hyperspecific region on antibody for binding and where antibodies bind to. each antigen has multiple but receptors are specific to one

Plasma Cell

Differentiate from B cells that bind to antigen. B cell loses everything except ER and ribosome in order to produce antibodies (identical to b cell receptors but detached).

Immunoglobin classes

Determined by the 5 different constant chains. Each are the same except for binding sites

IgM

• Pentamer

• Found on BOTH surface of B cell as antigen receptor and free in blood plasma as antibodies

• First class of antibodies released by B cells during primary response.

• Good at keeping pathogens in big clumps (phagocytosis)

IgA

• Dimer

• Found in bodily excretions ie saliva, breast milk

• Protects mucousla surfaces by preventing antigen binding to epithelial cells

IgD

• Monomer

• Found exclusively on B cells as antigen receptors

• B cell activation

IgG

• Monomer

• Most abundant in body

• Passes on to infant from breast milk

IgE

• Monomer

• Secreted by plasma cells skin and tissues lining GI and respiratory tracts

• Involved in allergies and parasites

• Binds to mast cells and basophils to sensitize them to subsequent binding of antigen, which triggers release of histamine that contributes to inflammation and some allergic reactions.

Antigen Presenting Cells

monocytes, macrophage, dendritic, B

Endogenous Antigen

antigen inside cell (virus, intracellular bacteria)

Exogenous Antigen

antigen from outside the cell. may be engulfed but will be acontained in a vacuole

Tumor Necrosis Factor

cytokine in inflammation response primarily produced by macrophages

Prostaglandins

hormone-like regulating substance also responsible for pain and blood clotting, realeased from inflammatory cells especially macrophages and neutrophils

Key Characteristics of Adaptive Immunity

specificity, tolerance of “self”, diversity, memory

Primary Response

• Adaptive immune response upon first exposure, antigen binds to B cell and starts preparing response

• Slow to kick in (2-3 weeks to fully turn on and make antibodies) and requires Th cell confirmation before producing antibodies

Secondary Response

• Subsequent exposures to same pathogen, results in faster, stronger, more specific response

• Body already has memory cells and recognizes pathogens and require

• Doesn’t require Th to verify

Interferon

Group of protein substances produced by infected cells to promote anti-pathogenic, neutralization responses and activate NK cells, signal from sick cell to warn others of infection

First Line of Defense

Anatomical (mechanical), chemical and microbiological defenses, all innate

Second Line of Defense

• Non-specific cell-derived

• Cytokines/chemokines, phagocytosis, inflammation

Anatomical/Mechanical Barrier

skin and mucous membrane

Skin

• most visible barrier and most difficult to penetrate

• high salt

• slightly acidic

• normally things can't grown on skin because of bad nutrition and low moisture

Mucousal Defense

• Lines digestive, respiratory, and genitourinary tract

• Hard to get through and extra mucous is produced when sick

• Mechanisms to propel microorganisms to areas where they can be eliminated

Chemical Defense

Low pH in vaginal and urinary tract, stomach acid, sweat, and lyzozymes (found in tears and saliva and break down bacteria)

Microbiological Defense

• the normal bacteria on skin fight invasive bacteria that cause disease

• normal flora--disrupting (taking antibiotics) can predispose a person to various infections

Species

Evolutionarily independent population of organisms with no interbreeding

Symbiosis

When species live on/near each other

Trophic

Species interactions involving food/consumption

Predation

• Trophic

• Always+ for species one (predator), - for species two (prey)

• ex carnivory, herbivory, parasitism

Carnivory

Trophic, animal to animal

Herbivory

Trophic, animal to plant

Parastism

parasite interaction with host, both predation and symbiosis

Competition

nontrophic, negative for both species due to fighting over limited resources

Mutualism

both species benefit, usually highly dependent or symbiotic

ex clownish and anemone

Commensalism

one species benefits and other is unaffected

ex squirrels living in trees

Amensalism

one species is unaffected, the other is harmed

ex elephant walking over grass

Continuum

Consequence of variable strength and asymmetry in interactions - species interactions are complex and do not have clear boundaries

Coevolution

Mutual evolutionary responses between interacting species, more likely to happen when interactions are frequent and predictable

Parasite

obtain nutrients from their hosts, consume parts of the host and hijack nutrients

ex: zombie ants and zombie snails