Innate Immunity: Recognition and Response

Innate Immunity: Recognition & Response

• Innate immunity relies on common pathogen traits for recognition and response.
• Pathogens are agents that cause disease like bacteria, viruses, or fungi.
• The body's first defense lines prevent pathogens from entering.
• Molecular recognition allows for the detection of nonself cells and molecules.
• Innate immunity is a defense active immediately upon infection in all animals.
• Adaptive immunity in vertebrates is activated following innate response and develops slower.

Invertebrate Immunity

• Chitin exoskeletons act as a barrier.
• Enzymes like lysozyme break down bacterial cell walls within the digestive system.
• Insect cells produce recognition proteins to bind molecules common to pathogens.
• Example: Toll recognizes fungal wall molecules.
• Insect hemocytes perform phagocytosis, entrapment, and antimicrobial peptide release.
• Insects have defenses against viruses, which consist of single-strand RNA.
• Single-strand RNA is converted into a double-stranded RNA within the host cell triggering specific defense.

Vertebrate Immunity

• Mammals' innate defenses mirror those of invertebrates for barrier defense and phagocytosis.
• Additional unique defenses in vertebrates include natural killer cells, interferons, and the inflammatory response.

Barrier Defenses

• Barrier defenses include mucous membranes and skin.
• Mucous membranes line and protect the respiratory, urinary, and reproductive tracts.
• Mucus traps and removes microbes.
• Most body fluids like saliva, mucous, and tears are hostile to microbes.
• Low pH level in the skin and digestive system inhibits bacteria growth.

Cellular Innate Defenses

• Mammalian innate immune cells detect, devour, and destroy invading pathogens.
• Neutrophils and Macrophages recognize groups of pathogens using Toll-like receptors (TLRs).
• TLRs recognize fragments of molecules characteristic of a set of pathogens.
• Immune response is aided by Dendritic cells, Eosinophils, NK cells, and Mast cells.

Phagocytic Cells

• Two main types of phagocytic cells in mammals are neutrophils, circulating in the blood, and macrophages, which migrate through out the body.
• Dendritic cells stimulate adaptive immunity and are found in tissues that contact the environment.
• Eosinophils discharge destructive enzymes against parasites.

Natural Killer Cells

• Natural killer (NK) cells circulate throughout the body and detect abnormal surface proteins, leading to cell death and inhibiting the spread of abnormal cells.

Local Inflammatory Response

• Inflammatory responses, involving heat and swelling, are initiated, with immune cells found in connective tissues, discharging cytokines to recruit neutrophils.
• Histamine is released, triggering blood vessels to dilate and become more permeable, increasing blood supply which produces the inflammatory responses.
• Signaling cycles continue the process of inflammation.
• Increased blood flow to the site delivers antimicrobial peptides.
• The result is pus an accumulation that is rich with white blood cells, debris, and dead pathogens from damaged tissue.
• Pus and excess fluid are absorbed as lymph via the lymphatic system following an inflammatory response.
• Macrophages engulf pathogens within lymph nodes that contain lymph.
• Dendritic cells stimulate adaptive immunity and migrate to lymph nodes.

Systemic Inflammation

• More extensive tissue damage can lead to a full body response.
• The secretion of molecules from the injured/infected tissue triggers additional neutrophil release from the bone marrow.
• The numbers of white blood cells in the bloodstream may increase significantly in severe infections within hours.
• Macrophages activated by pathogens elevated body temperature.
• Bacterial infections can cause excessive inflammatory response and septic shock.

Defense Proteins & Peptides.

• They trigger the production and release of attacking pathogens or impede their reproduction.
• Interferons defend innate defense by inhibit replication of viruses.
• To aid in defense, some interferons activate macrophages.

Complement System

• The complement system is composed of 30 blood plasma proteins.
• Activation occurs by pathogen surface substances.
• Reactions result as lysis of invaded cells.
• Function in both inflammatory and adaptive defense.

Evasion

• Outer capsules interfere with molecular recognition and phagocytosis, allowing pathogens to avoid destruction.
• Streptococcus pneumoniae is a major cause of meningitis and pneumonia.

Adaptive immunity: Pathogen-Specific Receptors

• Enhanced response due to previous exposure to a pathogen.
• It relies on two major lymphocytes or white blood cells: T cells, that mature in the thymus, and B cells mature in the bone marrow.
• Antigens are substances that elicit a T or B cell response.
• Antigens are foreign large molecules such as polysaccharides or proteins, and can also include bacteria toxins.
• Antigen receptors bind to antigens on T and B cells, that are specific to the pathogen molecule part.
• Immune systems produce million of antigen receptors.
• Lymphocytes generate one antigen variety receptor.
• Epitopes refers to the accessible antigen part that binds to antigen receptors.
• While T and B receptors have similar components, antigens are encountered in different ways.

B Cells

• Each B cell antigen receptor has 2 identical heavy and light chains in a Y-shaped formation.
• There constant regions are similar in B cells, but variable regions differs.
• The variable region determines the antigen specificity.
• Binding of B cell receptors is an early step in B cell activation which then produce soluble forms of receptor.
• This is called antibodies or immunoglobulin (Ig).
• Antibodies are shaped like a Y as B cell receptors.

T Cells

• Each T cell receptor has two polypeptide chains (α and β).
• The chain tips vary.
• The α and β chains form a single antigen-binding site.
• The rest is a constant region.
• T cells only bind to antigen fragments displayed or present on a host cell.
• Major histocompatibility complex (MHC) molecules bind these antigen fragments on the host cell's surface.
• The binding and transport of antigen fragments on the cell surface, in infected cells, is called antigen presentation.
• For adaptive immune response, T cells must bind both the antigen fragment and the MHC molecule.

B and T Cell Development

• Adaptive immune has four major characteristics; diversity of lymphocytes/receptors, immunologic memory and self-tolerance.
• Self-tolerance is the lack of reactivity against an animal's molecules and cells.
• B and T cells proliferate after activation.

B and T Cell Diversity

• The immune builds millions of antigen receptors by combining variable elements from a small number of parts.
• Different chains can be produced form the same gene via V, J and C region rearrangement.
• Diversity is built into the the structure of it genes.
• Encoding for a light chain has three segments: Variable (V), Joining (J) and Constant (C).
• V and J encode the variable region; C segment encodes the constant region.
• There is a single segment that contains the light chain gene.
• There are 40 different V and 5 different J segments.
• Pieces can be combined in 200 different ways.
• Combinations is more diverse in heavy chains.

Antigen development

• Functional Ig gene requires DNA rearrangement, assembled with recombinase to connect different V and J segments randomly in each B cell.
• These rearrangement goes to heavy/light chain genes, however heavy chains has additional gene segment, D.
• Every cell there is an allele of a one heavy chain and one light chain.
• Ig are permanent gene rearrangement and passed to daughter lymphocytes when divided.
• The rearranged genes are transcribed and translated to produce unique antigen receptors.
• VJ recombination Mutations causes even more diversity.
• Random DNA rearrangement, generates antigen receptors, but lymphocytes are tested for self-reactivity.
• Apoptosis, or programmed cell death, destroys B / T cells specific for the body's molecules.
• The remainder is nonfunctional, so only lymphocytes are now able to react to foreign molecules.

B and T Cell Proliferation

• Few body lymphocytes have antigen receptors and particular epitope.
• An antigen is exposed to steady stream of lymphocytes in lymph nodes, until there is a match.
• Mature lymphocytes binding to an antigen activates the lymphocytes bearing the receptor to initiate.
• Production of a clone of identical cells, a B or T cell undergoes multiple cell divisions, through clonal election when activated .
• Against the antigen, some effecter cells immediately become the active cells.
• Effector cells are plasma that secrets antibodies.
• Memory cells can give rise to effector cells and are long lived if the same antigen occurs again.

Immunological Memory

• Long-term protection against diseases is due to immunologic memory.
• A clone of lymphocytes is formed and represents the primary immune response when first exposed to a antigen.
• The secondary immune response is when memory cells facilitates faster/greater and prolonged response from T and B memory cell reservoir's.

Adaptive Immunity

• B and T lymphocyte defenses can be branched into cell-mediated (infected host cells destroyed by T cells) and humoral immune responses (toxins and pathogens neutralized by antibody).

Helper Cells

• Helper T cell activates both humoral and cell-mediated immune responses and requires a foreign molecule and antigen receptor.
• Displays on T cells and antigen-presenting cell via MHC.
• Antigen-presenting cells have class I and class II. MHC molecules
• MHC I are all cells, while MHC II are APC.
• Class II provides a molecular signature for which antigen-presenting cells can be recognizable by interacting with CD4 on T cell.
• Cytokine is exchanged that helper T binds to antigen in the MHC II when it comes to antigen receptors.
• Helper T is stimulate and make set of cytokines.

Humoral Immune Response

• By clonally selected B cells that have secrete antibodies, characterizes the humoral response.

Activation of B Cells

• Involves proteins, helper T cells and pathogens and begins with activation of B cells.
• A cell takes few molecules via receptor-mediated endocytosis.
• For an active helper T cell, presents a class II MHC protein and antigen fragment

Antibody.

• The most antigens recognized by B cells include multiple epitopes.
• Plasma produces an activated B cell by identical plasma cell production.
• B cells created by one antigen that created plasma produces against common antigen.
• Rather than marking pathogens for destruction an inactivation, do not kill pathogens

Defense:

• Antibodies helps prevents viral surface proteins.
• Antibodies supports Bacteria Antigens, and promotes phagocytosis.
• Antibodies and facilitate phagocytosis, help in immune.
• Proteins system of complement may utilize antibodies.
• Binding of a complement pore to form in the membranes.
• Waters and ions flow to cells by causes an increase of lysis.
• B cells may increase to express forms of immunology with great heavy.
• IgC differes membrane and 4 soluable's such. IgA, and IG,

Cell-Mediated Immune Response

• Includes Help T Cells/Antigen Presenting.
• T cells and APC's displaying an a matches cytotoxic I, that cells by binding MH.
• Cytoxic t nearby activates from an T cell binding.
• Activated Cytotoxic maturation of cells into a Effector T from maturation of cell.
• Toxic proteins used for kill by a Virus Intracellular Pathogens.
• Foreign Fragment of foreign Protein made to infected from MHC,

Humeral and Cell-Mediated

• Secretes protein that targets disruption.

• Immunization

• A second immune basis for immunization.

• Artificial introduced for the body for immune memory/adaptive.

• Vaccines from microbial from that kills the protein.

• Managed Pathogens are in vaccinations

• Vaccine is safety caused to problems.

Passive Immunity

• Active Immunity develops after pathogen invades to a immune response.

• Passive Immediate's short is an immunization for antivenin.

• Antibodies neutralizes toxins of snake venoms.

• Antibodies as tools is products after the animals

• Monocolonal prepared from a single is an eptiomes

• Antibody from a used in diagnoses medical

• Detection home to Monocolonals

• Can identified Therapies for viruses

• Transfers from someone to defense for not attacked.

Grouping

• Grafts, recipients, and immune for suppression

• Antigens of cells for B antigens and O

• Antibodies exits to types non blood

• Transfusion of blood can chills

• Malfunction of the kidneys.

• It has functions for system

• Autoimmune diseases can a response of allergens

Allergic

• Hay is made causes a pollen grain -Induces triggers and chemicals
• Nose allergy for muscles.

Autoimmune Diseases

• In immune the self intolerance immune system.
• Body and Immune turns is to lupus breakdown.
• Antibody Arthritis, kidney Rashes
• Auto Immune condition is condition a Type ! Diebetes for heridity.
• Exercise Exertion
• Exercies functions increases leads more infections.
• Stress can cause hormones to disrupt, but resting can help.

Deficienies.

• Genetic has development with deficience

• Agents is after deficience is caused

• Avoidance

• Pathogenic for immune

• Variation

• Some host a pathogens to the hosts

• A simulus emotion to a virus

• Infected by system

• Mutation rate in the is is the immune.

• Abolishment to the immune

• H I V leads to syndrome aids

• Defeat usually that immune

• Transmission what is education

• Immunity from is for inactivated

• Viruses in cancers

• Cancer what in caused defenses scientists.

• Humans 6 had to viruses

• Some of those 6 viruses includes herpes and papilloma.