Microbiology Lecture - Immunology

8/14/2019 Microbiology Lecture - Immunology

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I MMUNOLOGY

I MMUNOLOGY

Mark Michael J. Cuevas,

an introduction


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Resistance

The ability to ward off diseasethrough our defenses

Immunity

Ability of the body to specificallycounteract foreign organisms orsubstances called antigens


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Immune System

Functional system that recognizes foreignmolecules and acts to inactivate or destroy it

Composed of many interdependent cell types thatcollectively protect the body from bacterial,

parasitic, fungal, viral infections and from thegrowth of tumor cells

Can engulf bacteria, kill parasites or tumor cells orkill viral-infected cells


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BONE MARROW

Organs of the Immune System

Produces B-cells, natural killer cells,granulocytes and immature thymocytes,

in addition to RBCs and platelets


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THYMUS


Produces mature T-Cells, which are thenreleased into the bloodstream


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SPLEEN


Immunologic filter of the blood

Made up of B-cells, T-cells, macrophages, dendriticcells, natural killer cells and RBC


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LYMPH NODES


Immunologic filter for the bodily fluidknown as LYMPH

They are connected by lymph channelsand capillaries, which remove foreignmaterial from the lymph before it enters

the bloodstream


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I MMUNITY

Ability of the host to defend against a

particular infectious agentIt results from the production ofspecialized lymphocytes and antibodies


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AcquiredImmunity

Immunity that results from the active

production or receipt of antibodies duringones lifetime


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Types of acquired immunity

NATURALLYACQUIREDIMMUNITY

ARTIFICIALLYACQUIREDIMMUNITY

NATURALLYACTIVE

ACQUIRED

IMMUNITY

NATURALLYPASSIVE

ACQUIRED

IMMUNITY

ARTIFICIALLYACTIVE

ACQUIREDIMMUNITY

ARTIFICIALLYPASSIVE

ACQUIREDIMMUNITY


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1. The baby has received a BCG vaccine at thetime of its birth

2. A 5-year old child contracted chickenpox andthe disease did not recur thereafter

3. The community nurse gave OPV to a 6-monthold infant

4. The mother breastfeeds her newly born childevery four hours

5. The doctor administered Rabies ImmuneGlobulin to a 17-year old male who was

admitted in the ER due to dog bite


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VACCINES

A suspension of organisms or fractions of organismsthat is used to induce immunity


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Types of vaccines

ATTENUATEDVaccine

INACTIVATED

VaccineCONJUGATEVaccine

Killed pathogens

Bacterialcapsular antigen

Weakened oravirulent


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Types of vaccines

SUBUNIT Vaccine

TOXOID Vaccine From ExotoxininactivatedAntigenic

portions of apathogen

DNA VaccinePlasmidsinjected into

skin/muscletissue

AUTOGENOUS

Vaccine

Isolated bacteriainjected to

induce more


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Antigenic variation

A change in surface antigens of some viruses


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Humoral Immunity

Duality of the immune system

Also termed as ANTIBODY-MEDIATEDIMMUNITY

Involves the production of ANTIBODIES

B-Cells are responsible for the production ofantibodies


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Cell-mediated Immunity

Duality of the immune system

Involves specialized lymphocytes calledT-cells

Most effective against bacteria and viruses located

within phagocytic or infected host cellsAlso an important factor in our defense against cancer


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Humoral Immunity

Nature of antigens

Antigenic Determinants (Epitopes) component of a bacterial cell wall that iscapable of stimulating the production ofantibodies

Haptens small molecules that it is notoften antigenic unless it is attached to acarrier molecule


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Humoral Immunity

Nature of antibodies

Belong to a class of glycoproteins calledImmunoglobulins

Highly specific and only react with only one antigenicdeterminant

Basic structure resembles the letter Y

- 2 identical heavy and light polypeptide chains

- 2 antigen-binding sites

- Fc region

- chains are connected to each other bydisulfide bonds


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Immunoglobulin classes

Only Ig that can cross placental barrier Long-lived and most abundant in serum

Protect against bacteria and viruses, neutralizebacterial toxins and enhance effectiveness ofphagocytic cells

IgG


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Found in saliva, tears, seminal fluid,colostrum, breast milk and mucoussecretions of nose, lungs and GIT

Most abundant in the body but short-lived

Prevents attachment, colonization andinvasion of pathogens

Protects infants from GI infections

IgA


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Does not cross the placenta

First to appear in response to exposure to anantigen

Bactericidal to gram-negative bacteria

Relatively short-lived

IgM


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Produced in response to allergens

Found on the surfaces of basophils and mast cells

IgE


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Found in large quantities on the surface of B-cells, some in the blood and lymph

Function is unknown

Act as antigen receptors on the surface of B-cells

IgD


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Blebbing Necrosis

B-cells do not encountera stimulating antigen

Apoptosis(programmedcell death)

Attractsphagocytes

Inflammation


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Cell-mediated Immunity

Chemical messengers

Inhibitory or excitatory

Cytokines /Lymphokines


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Types of cytokines

Stimulates THcells in presence

of antigens

Attracts phagocytes ininflammatory response

Interleukin-1


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Types of cytokines

Proliferation of antigen-stimulated TH

cells

Differentiation of B-cells

Activation of TC cells and NK cells

Interleukin-2


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Types of cytokines

Induces migration ofleukocytes into infected areas

Interleukin-8


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Types of cytokines

Inhibits viral replication

Increases activity of macrophagesagainst microbes and tumor cells

Gamma-Interferon


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Types of cytokines

Cytotoxic to tumor cells

Enhances phagocytic activity

Tumor Necrosis Factor-Beta


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Types of cytokines

Stimulates formation of red andwhite blood cells from stem cells

Granulocyte-MacrophageColony Stimulating Factor

S i li d


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Specializedlymphocytes

Developed from stem cells inthe bone marrow

Precursors migrate and reachmaturity in thymus

Mature cells migrate to variouslymphoid organs

T-Cells


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Types of t-cells

Influence the activity of other

immune system cells

Helper T-Cells


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Types of t-cells

Destroy target cells on contact

May kill cancer cells and cellsof transplanted tissue

Cytotoxic T-Cells


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Types of t-cells

Associated with allergic reactions

DelayedHypersensitivity T-

Cells


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Types of t-cells

Regulate immune response by

turning it off

Suppressor T Cells

Specialized


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Found in resting state

Phagocytic cells

Stimulation is primarily byingestion of antigenic materialor by cytokines

More effective

ActivatedMacrophages

Specialized


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Capable of destroying other cells

Can also attack large parasites

Are not immunologically specific

Natural Killer Cells


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Bodys Immune Response

1.Discriminatory

2.Specificity

3.Anamnesis

4. Transferability of Living Cells

4 Characteristicsof ImmuneResponse


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First exposure to antigen

Primary Response

Characteristics:

Long-latent period

Slow rise in blood titer Low peak short plateau

Period of decline as fast as rate of increase


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Subsequent exposure to antigen

SecondaryResponse

Characteristics:

Short-latent period

Rapid increase of titer Peak of antibodies produced is very high

Extended plateau


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Thank You for Listening!

Microbiology Lecture - Immunology

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