Adaptive Immune response

Adaptive immunity

when overcomes innate/cause infection, specific for organism, has memory, 2 types - Antiboy(humoral) and Cell mediated

Replicate in nucleus

orthomyxoviridae (flu) and Retrovirus (HIV/HTLV)

Antibody mediated immunity target

extracellular, parasites, freevirus

Humoral mediated immunity target

intracellular, virus

Dendritic cells

regulators, bridge innate and adaptive immunity

T helper cells

CD4 surface receptors, deliver cytokines that excites macrophages and B cells

B cells

mutate to differientiate, make into plasma cells (antibodies and memory), precursor is Hemapoitic stem cells

T cytotoxic cells

CD8 surface receptor, mainly for virus and infected cells

Humoral immunity

antibody mediated (protein from plasma), target naked virus and parasites, B cells, fast response, MHCII proteins, destruction or neutralization, in extracellular fluids

Cell mediated immunity

T cell mediated, target intracellular pathogens and cancer cells, T cells, slow response, MCHI proteins, Cell lysis and programmed death, in antigen presenting tissue

MHC class II proteins

only in antigen presenting cells (macrophage/mass cell, B cells, Dendritic), trigger humoral immunity

Antigens

Antibody generator, reacts with Ab or Ag receptors on lymphocytes, doesn’t always trigger immune response, Bcell triggered to proliferate and differentiate into plasma cells

Immunogen

Antigen that can induce immune response

Antigenic/immunogenic

relative ability of antigen to elicit immune response, determined by epitopes

Epitopes

discreet region of antigen, recognized by adaptive immune response, proteins (10-15AA), interact with paratope, in pathogen and microbes

Paratope

part of antibody arm, where epitopes binds

immune system maturation

at 15 yrs, vaccine can’t elict antibody + cell mediated response any more

Antibody

main component of humoral immunity, produced by B lymphocytes, neutralization of free floating particles, cause B cells trigger proliferate and differentiate into plasma cells, Y shaped proteins

plasma cell

produce antibody and memory cells, from B cells

Antibody structures

2 functional regions, 2 identical arms and 1 stem, arms bind specific antigens - triggers classical pathway, stem (crystylized region) tags antigen for destruction by other immune system components

Light chain

2 types - lambda and kappa, based AA sequence on constant region(110 constant and 110 variable), any B cell produce Ab of one specificity, both chains identical

Heavy chain

5 types - lambda/mu/alpha/sigma/eplison, based AA sequence on constant region(450-550), gives class of antibody types

Serum vs plasma

serum is without clotting factor whereas plasma has clotting factors

IgG

75% of serum immunogloblins(most abundant), monomeric, 4 subclasses (igG1 most prevelent), Opsonization, Neutralizes virus/toxins, passive immunity (cross placenta), main Ab in secondary respnse

IgM

monomeric when attached B cell and Pentameric in Serum (held by J chain), first Ab produced in primary response, Ag receptor on B cell, activates innate defense(classical pathway), Aggluinates particulates

IgD

monomeric, found serum and B cell surface, very low amount, participates mucosal immunity, coexpress w/ IgM, play role establishing immune tolerane, stimulates B cell to mature into plasma cells

IgA

in mucous membranes, dimeric in secretions, neutralize bacteria/virus, prevent attaching mucous membranes, passive immunity (breast milk)

IgE

monomeric, low amount in serum, Ag recepto on MAST cell (tissue) and Basophils (blood), anaphlactic hypersensitivity (release histamines) - reacts foreign particles

6 functions of antibodies

Cross linking(agglutination), Neutralization, Complement activation, Opsonization, Ab dependent cytotoxicity, Immobilization and preventing adherence

Antibodies and crosslinking (agglutination)

antigen get stuck together, reduce number of infectious units

Antibodies and Neutralization

Ab binds to inactivates toxins/bacteria/virus, blocks attachment sites

Antibodies and complement activation

ab bind bacteria, starting point for complement pathway, MAC attack

Antibodies and Opsonization

Ab flags down phagocytic cells to engulf and destroy antigen, crystallized regionvery specific for phagocytes

Antibodies and Ab dependent cytotoxicity

Ab flags down immune system to destroy abnormal/infected cells

Antibodies and Immobilization and preventing adherence

Ab binds to flagella to stop pathogen from moving, pili stops bacteria from colonizing

T lymphocytes

Cell mediated immunit, generate in bone marrow and mature in thymus, only recognize Ag presented in own cells, bind peptide from MCH complex, activation help macrophages kill intracellular parasites (release cytokines)

T cell receptor

bind complex of MHC and pepetide, helps macrophage kill intracellular parasites/inhibit replication, release cytokines

T lymphocytes types

Cytotoxic (CD8) - destroy infected/cancerous cells and recognize Ag presented by MHC class I, Helper (CD4) - activates macrophage(1)/ B cells (2) and recognize Ag presented by MHC classII

MHC class II

in Antigen presenting cells (B cells/Dentritic/Mast/Macrophage)

non nucleus cells (ex RBC) surface proteins

predetermined, can’t communicate when infected

MHC class I

all nucleated cells, communicate when infected

IFNy and TNF-alpha

signal molecules (macrophage activating)

Lymphoid system

tissue and organ designed to bring B and T cell into contact with Ag, organs - Thymus/spleen/lymphnodes, Lymphatic vessel - carry lymph (fluid)

Haemopotoetic stem cell

myeloid cells and Lymphoid cells, precursor in bone marrow

Lymphoid cells

Natural killer, T cytotoxic, T helper, B cells

Primary lymphoid organs

bone marrow and thymus, both B and T cell originate in Bone marrow, T cell mature in thymus, some B cell mature in Spleen/lymphnodes

Secondary lymphoid organs

where mature lymphocyte gatehr to collect Ags, strategic position (spleen - blood/lymph nodes - lymph), lymphocytes proliferate once makes contact with specific Ag, MALT less organized version

B and T cell receptors

difference in surface markers (CD molecules), B cells - surface immunoglobin, T cells - T cell receptors (TCR) (all same expect CD4+CD8)

Clonal Selection and Expansion of B lymphocyte

each cell recognizes and responds 1 epitope, correct binding of Ab and Ag selects, produce population of clones (expansion), most need accessory signal from another cell (th) before ceactivation (prevent IR agaisnt self)

B cell maturation and antibodies

immature B cell has IgM, undergoes RNA splicing to gain IgM, gros recombination (change heavy chain)lead to secretor B cells with IgA/G/E

B1 cells

from bone marrow, mature in respiratory track, secrete IgM cells

proB cells

from bone marrow, secrete IgD cells, in spleen - IgM

Clonal selection and expansion of T lymphocytes

similar process as B cells, some release cytokines (cytotoxic function), fraction become memory cells

Memory cell surface receptors

T memory cells - CD45RO, B memory cells - CD27 + IgA/G/E

memory cells

more readily stimulated by antigen, basis principle of vacconation, greater combining power (B cell mutation/selection + T cell increase adhesion)

Toxoid

inactivated form of toxin, inactivated by heat or chemical, only trigger B cell immunity (humoral)

Lymphocyte stimulation - T dependent

need conformation (Th signal) befores B cell activation, very specific (IgA/G/E)

T dependent lymphocyte stimulation steps

pathogen released peptide capture by B cell/APC (MHCII), B cell not active until conformation from APC, T helper release CTLAY when presented pathogen peptide activated T helper cells, activated T helper releases interleukins (IL-4) activating B cells, release antibodies

CTLA4

looks like immunoglobin, brake for T helper cell activation

Lymphocyte stimulation - T independent

Polyclonal activation and Repeating determinants, not mediated by T helper cells, produce IgM (no memory/non specific)

Type 1 indepent antigen activators

superantigens, polyclonal, LPS and toxins

Type 2 independent antigen activators

repeating determinants, repeats same antigens, polysaccharides in capsules

Cytokines

signal molecules - soluble intracellular communication, control of diesase and develpment of pathology (inflammatory response), Interferons

Interferons (IFN)

made by infected cells, tell other cell virus is in body, induce antiviral state

Antiviral state

prevents viral genome replication, degrade viral mRNA or inhibits protein synthesis

cytokine and Thelper cells

define production of Thelper cell subset, mutual antagonsim between subsets - regulates

Immune system regulation

depending amount of antigens, Ag given to APC causes Th stimulation, B cell produce IgM which further stimulates, once Ag decrease IgG supresses?