Chapter 15

Adaptive Immune Response

Matures and Changes throughout a lifetime

Adaptive immunity - protection provided by these immune responses

• involves B and T cells

Take a while to build a specific defense following exposure

• Innate immunity protects during that time

Adaptive immunity has memory

• memory - greatly enhanced response to re-exposure

• principle behind vaccination

• has molecular specificity

Immune system can discriminate between healthy and non-health self so as not to continuously attack itself

• Autoimune disease caused when function is broken

re-infection by the same agent is usually. result of avoiding host defenses not a lick of response

Strategy of the Adaptive Immune Response

Types of Response

Primary

• first exposure takes the adaptive immune response aprx. a week to develop, leaving protection to innate immunity

Secondary

• enhanced, does not take long

strategies

• Humoral Immunity - attempts to eliminate extracellular antigens

  • bacteria, toxins, or anything in bloodstream or tissue fluids that shouldn't be there like viruses

• Cellular Immunity - attempts to eliminate antigens that have infected a cell such as a virus

Immune response is tightly regulated so no unnecessary damage is done

Humoral Immunity

B-lymphocytes (B cells) are the major players

Extracellular antigens trigger B-cells to multiply and differentiate into plasma cells

Plasma cells produce antibodies - Y-shaped proteins that bind a specific antigen

Some B cells form memory B cells - live a long lime as a 13 Cen making it possible to launch a quick response upon re-exposure

Antibodies have two parts

• Two identical arms that bind the antigen

  • the amino acid sequence is variable

  • Yields specify

Antibody binding protects by preventing an antigen from binding its target by flagging down phagocytes to get rid of the bound molecule (opsonization)

Each B cell carries B-cell receptor which is a membrane-bound derivative of the antibody it is programmed to make.

Binding of the antigen to the B cell

allows it to multiply.

lots of 13-cells or made during the initial response, but only ones that replicate are the ones that can bind the antigen

• 1B cell needs a TH cell to confirm antibody is dangerous clonal selection and expantion of Lymphocytes

clonal selection-process by which a given antigen binds to the specific antigen receptor on a lymphocyte (B at T ang

• Albus cell to proliferate generating clones of its sent

• cornal expansion

target (a teaching) and

Nature of Antigens

Antigen-anything that reacts with an antibody or binds an antigen receptor on a lymphocyte

can be, Microbes, Microbe products, plant pollen Imminogen-antigen that elicits an immune response

can set differing immune responses-

protiens and poly saccrides tend to get a Stronger respons than lipids and nucleic acids

Antigen and Immunogenitic are interchangable

Antigens are large molecules

• certain regions are recognized

• * Antigenetic determinants / epitopes Antigens are also called immunoglobins Two arms called fab regions bind the antigen

Stem is fc region enlists other parts of Immune system

There are two heavy chains and two light chains

Disulfide bonds (S-5) join chains

5 classes of antibodies - human imminoglobins

• Ism, IgG, = IgA, = TSD,ISE =

• distinguished by the stem region

Antibodies

variable Region

• Areas of antigen binding ends of Fab regrong, Differing amine acid sequence

• Area specific for binding its antigen

• binds using many non-covalent interactions binds strongly but is reversible leaving the two molecules unchanged

Constant Region

• All FC region and part of the light and heavy chains in fab regions

• same for all molecules ot a given class

• Talks to other components of the immune system

outcomes of Antibody Antigen Binding

Neutralization

• A toxin or virus normally needs to bind the cell surface to begin to cause

damage

• cannot perform if coated

Immobilization and Prevention of Adherance

• Binding to flagellum and pili prevent motility or attachment

• If these function are essential

• protect host

Agglutination and Precipitation

• Marry antibody /antigen binding interections can secur forming large complexes

• can gather together disperse antigens and have them engulfed simultaneously by phagocyte

• can precipitate solvable antigens

opsonization

• Molecules can bind an antigen making it easier for them to be engulfed

• Ig G molecules

• macrophages and neutrophiles have receptors for fC region of this antibodies

complement system Activation

• Antibody Antigen bilding can trisser the classical pathway of the component system Antibody-dependent Cellular Cytotoxixity

• multiple Ig G binding to a cell becomes targeted for destruction by certain cells like natural killer cells

Immunoglobin classes

Have same basic monomeric structure

Each class has different constant region of

heavy chain

some form multimers of basic monomeric structure

Each Class has distinct functions and properties

Immunoglobin M-Ig M

• 5%-13% of circulating antibodies

• first class produced in response to

T- independent antigens

• pentameter LP binding sites) good at agglutination,

precipitation large

• ussualay can't get into tissues so pimarily for bloodstream infections

• most efficient class for initiating the classical pathway

Immunoglobin G (IgG)

• 80%-85% of total

• in blood, vessels, and tissues

• around longest - 21 days half life

• first and most abundant class during secondary

Immune response

• protect by neutralization, aggulatination, opsonization, complement activation, ADCC

• only class that can cross placenta

• maternal IgG antibodies protect newborns for

3-6 months due to bug half life

• Available in colostrum

Immunoglobin A (ISA)

• 1000-13% of total-most abundant class

made, not in blood

• most secreted, dimer, secretory IgA

• secreted form in mucors membranes and

saliva, fears, and breast milk

• protection due to direct binding-neutralization and preventing attachment

Immunoglobin D Ig D

• less than 10 total

• Development and maturation of the antibody response

• Don't really know yet

Immunoglobin E- IgE

• barely detectable

• not free circulating, f region bound to

mast cans and basophiles

-Antigen binds Ise Molecule and attached cell releases Chemicals like histamine, cyto vines, and compounds that elicit the infurmatory response -Thoughts to be important in parasite elimination

- Allergies pear when bound Ise encounters harmless material like dust and pollen

Primary response characteristics

following first exposure, it takes 10 days to two

weeks to get detectable levels of antibody in the blood

Everything is going on at this time

• Naieve B cells bind antigen and present it to TH cells. Binding results in B-cell activation and proliferation

• some continue to divide and some differentiate into plasma cells secreting thousands of antibodies

B cells undergo changes to enhance the

immune response

formation of memory cells

• some B cells swich to long lived memory cells

• years

• Give fast and effective secondary response

• can live without antigen binding

Secondary Response characteristics

second encounter with particular antigen

significantly faster, more effective than the

primary response

Pathogens usually eliminated before causing harm

vaccination relies on this

memory B cells responsible

more cells are able to respond to the

reinfecting antigen

• 13 cells and resulting antibodies are good at binding the antigen and an effectively

respond to even low levels of antigen

Strategy of Adaptive Immune Response

cellular Immunity

• T lymphocytes (T cens)

• Cytotoxic T cells and helper Tens

• Both have surface moleute - T cell receptor- enabling the cen to recognize a certain antigen.

• Does not recognize free antigen, must be presented by bodies own cells

• T cells form memory cells

• regulatory T cells (T Suppressor cells)- prevent immune system from responding to

healthy 'self' cells

• Both types of T cells must be activated before they can multiply

• Activated by dendritic cells

- After binding, T cells proliferate and differentiate but require another moteale to confirm the antigen is dangerous

• Dendrite cells Cinnate immunity) provide second opinion

• T cells differentiate into effector cells

• effector helper T cens - contribute to humoral and cell mediated immunity activates B cells and meeophages and stimulate other T cens as well as other immune responses

• Effector cytotoxic T cells-responds to intracenular antigens: induces apoptosis to destroy infected or aneerous

self cells

Natural Killer cells

come from lymphoid stem cans

Augment adaptive immune response

Do not have antigen binding receptors

Antibody dependent cenular toxicity - kills cells bound

• "antibody

NK cells have fc receptors for IgG antibodies

when multiple receptors on NK surface bind the

Fe regions the NK can delivers perforins and proteases to the targeted can inducing apoptosis

NK cells can also will host cells that do not have MetH class I protiens on their surface and are under stress

• lack of MCH Class I complex not normal

• other indicators of stress appear on surface

• Important because it is a sign a virus has

circumvented antigen presentation

Anatomy of Lymphatic system

lymphatic system-collection of tissues and organs that brings B and T cells in contact with all antigens that enter the body

ensures appropriate lympocyte encounters it's antigen

1. vid flows through lymphatic vessels

oxygenated blood travels through the heart and longs and through the apilaries.

Fluid from blood filters out into surrounding tissues carrying oxygen and nutrients

fluid reabborbs into epilarries on way back

to heart and lungs

some enters the lymphatic vessels that already contain white blood cells and antigens All travels to lymphmodes where all protien and cell material are removed and lymph empties into Capilaries

Primary Lymphoid organs

• bone marrow and thymus

• where stem cells mature into B and T cells

Secondary Lymphoid organs

• lymph nodes, spleen, tonsils, adenoids, appendix

• stratisec locations for immune response

-sites were adaptive Immune responses are innitiated

• facilitate interactions and transfer of atokines between ans of Immune systeme

• lymphocyts can gather contact various antigens

Lymphocyte Development

1. cells bone marnow

2. cells-Thymus

Generation of Diversity

Impersise Joining

various segments are joind during recrangement

nucleotides can be deleted or added between

sectors, changing the reading phrame

Two Breen have same combination but

diffent antibody

combinatorial Assosiations

Antibody binding Sites are made of light chains and

heavy chains of which contribute to diversity

• Both acquire diversity through rearangement and impercise joins

• They are then combined