The Immune SystemThe Immune System

Donna Howell

Medical Microbiology

Blacksburg High School

Unit 13

Overview of Immune SystemOverview of Immune System

Our immune systems Our immune systems consist of two main consist of two main types of resistance:types of resistance:

1.1. Non-specificNon-specific – body – body’’s s defense against ANY defense against ANY type of pathogentype of pathogen

2.2. SpecificSpecific – body – body’’s s defense against a defense against a SPECIFIC pathogenSPECIFIC pathogen

The Immune The Immune SystemSystem

Lymph nodes:  Lymph nodes contain billions of white cells, multiplying rapidly to fight the invading germs. During illness they fill with millions of extra white cells and also dead germs.Bone marrow: Produces all white blood cells. Spleen: An immunologic filter of the blood, the spleen is made up of red and white blood cells. Adenoids: The adenoids are found in the top and back of the throat and help guard against illness by identifying harmful bacteria, fungi, and viruses in food or the air. White blood cells in the adenoids incapacitate the invading germs and help produce antibodies to fight future infections.

Non-Specific ResistanceNon-Specific Resistance

First line of defense:First line of defense:

• Intact skinIntact skin• Mucous Mucous

membranes & membranes & secretionssecretions

• Normal flora on Normal flora on bodybody

Non-Specific ResistanceNon-Specific Resistance

Second line of defense:Second line of defense:

• Phagocytic white Phagocytic white blood cellsblood cells

• Inflammation and Inflammation and feverfever

• Antimicrobial Antimicrobial substancessubstances

Specific ResistanceSpecific Resistance

Third line of defense:Third line of defense:

• Specialized white Specialized white blood cellsblood cells

• AntibodiesAntibodies

Skin & Mucous MembranesSkin & Mucous Membranes

• Mechanical factors – Mechanical factors – intact skin, intact skin, tears, cilia in throat, epiglottis, urine, tears, cilia in throat, epiglottis, urine, vaginal secretionsvaginal secretions

• Chemical factors – Chemical factors – sebum, sebum, perspiration, gastric juice, vaginal perspiration, gastric juice, vaginal secretions.secretions.

• Normal flora – Normal flora – normal bacteria act normal bacteria act as a barrier to other microbes trying as a barrier to other microbes trying to enter by competing for nutrients to enter by competing for nutrients and producing toxic substances.and producing toxic substances.

Blood ComponentsBlood Components

There are two main There are two main components of our components of our blood:blood:

1.1. Liquid part – called Liquid part – called plasmaplasma

2.2. Cells – 3 types:Cells – 3 types:

1.1. Red blood cellsRed blood cells

2.2. White blood cellsWhite blood cells

3.3. PlateletsPlatelets

Red Blood CellsRed Blood Cells

The purpose of red The purpose of red blood cells is to blood cells is to carry oxygen to carry oxygen to our tissues.our tissues.

PlateletsPlatelets

Platelets aid in the Platelets aid in the clotting of our blood clotting of our blood when we are hurt.when we are hurt.

Platelets

White Blood CellsWhite Blood Cells

White blood cells, or White blood cells, or leukocytes, are the cells leukocytes, are the cells that are part of our that are part of our immune system. They immune system. They are the phagocytic cells. are the phagocytic cells. This is what pus is made This is what pus is made out of. There are 5 out of. There are 5 main types, and will main types, and will each be discussed on the each be discussed on the next 5 slides.next 5 slides.

NeutrophilsNeutrophils

The purpose of The purpose of neutrophils is neutrophils is strictly strictly phagocytosis of phagocytosis of bacteria, viruses bacteria, viruses and fungi. and fungi. Comprise 60-70% Comprise 60-70% of our wbcof our wbc’’s.s.

BasophilsBasophils

Basophils migrate to Basophils migrate to damaged tissues and damaged tissues and release histamine to release histamine to promote promote inflammation and inflammation and heparin to inhibit heparin to inhibit blood clotting. blood clotting. Make up <1% of our Make up <1% of our wbcwbc’’s.s.

EosinophilsEosinophils

Eosinophils Eosinophils moderate allergic moderate allergic reactions as well as reactions as well as defend against defend against parasitic infections. parasitic infections. Make up 2-4% of Make up 2-4% of our wbcour wbc’’s.s.

MonocytesMonocytes

Monocytes are Monocytes are also phagocytic also phagocytic cells. They cells. They comprise 3-8% comprise 3-8% of our wbcof our wbc’’s.s.

LymphocytesLymphocytes

Lymphocytes are Lymphocytes are the major players the major players in specific immune in specific immune reactions, and some reactions, and some produce antibodies. produce antibodies. Comprise 20-25% Comprise 20-25% of our wbcof our wbc’’s.s.

PhagocytosisPhagocytosis

This is the ingestion of a This is the ingestion of a microorganism by white microorganism by white blood cells. 4 stages:blood cells. 4 stages:

1.1. Chemotaxis – Chemotaxis – chemical chemical attraction of wbc to attraction of wbc to organismorganism

2.2. Adherence – Adherence – attachment of attachment of wbc to surface of organismwbc to surface of organism

3.3. Ingestion – Ingestion – pseudopods pseudopods engulf the organismengulf the organism

4.4. Digestion – Digestion – digestive digestive enzymes digest organismenzymes digest organism

Phagocytosis – The ProcessPhagocytosis – The Process

InflammationInflammation

Damage to the bodyDamage to the body’’s s tissues triggers a tissues triggers a defensive response defensive response called inflammation. called inflammation. 4 signs and 4 signs and symptoms:symptoms:

1.1. RednessRedness2.2. PainPain3.3. HeatHeat4.4. SwellingSwelling

InflammationInflammation

The purpose of The purpose of inflammation is to inflammation is to destroy the invading destroy the invading pathogen, or to limit pathogen, or to limit the effects on the body the effects on the body by confining or by confining or walling off the walling off the pathogen and itpathogen and it’’s by-s by-products.products.

InflammationInflammation

3 stages of inflammation:3 stages of inflammation:

1.1. VasodilationVasodilation – blood vessels – blood vessels dilate and become dilate and become permeable, thus allowing permeable, thus allowing white blood cells to move out white blood cells to move out of blood stream and into of blood stream and into tissuetissue

2.2. PhagocytosisPhagocytosis – white blood – white blood cells engulf the pathogen and cells engulf the pathogen and die, forming pusdie, forming pus

3.3. Tissue repairTissue repair – body replaces – body replaces dead and damaged cellsdead and damaged cells

Pus Smear

Process of InflammationProcess of Inflammation

FeverFever

This is the bodyThis is the body’’s s response to any response to any injury. High injury. High temperatures temperatures serve to speed up serve to speed up the bodythe body’’s s reactions, thus reactions, thus allowing it to heal allowing it to heal quicker.quicker.

Antimicrobial SubstancesAntimicrobial Substances

The body also produces two The body also produces two main antimicrobial main antimicrobial substances:substances:

1.1. ComplementComplement – proteins – proteins in blood that participate in blood that participate in the lysis of foreign in the lysis of foreign cells, in inflammation, cells, in inflammation, and in phagocytosis.and in phagocytosis.

2.2. Interferons Interferons – these are – these are antiviral proteins that antiviral proteins that interfere with viral interfere with viral reproductionreproduction

The Immune ResponseThe Immune Response

Immunity is a SPECIFIC Immunity is a SPECIFIC defensive response by defensive response by our bodies. Also our bodies. Also called acquired called acquired immunity because we immunity because we only acquire it when only acquire it when our bodies encounter a our bodies encounter a specific pathogen.specific pathogen.

Acquired ImmunityAcquired Immunity

There are two types of There are two types of acquired immunity:acquired immunity:

1.1. Naturally acquiredNaturally acquired – – happen through happen through natural exposure to natural exposure to pathogenspathogens

2.2. Artificially acquiredArtificially acquired – – we deliberately we deliberately expose our bodies to expose our bodies to a pathogen, thus a pathogen, thus stimulating the stimulating the immune responseimmune response

Naturally-Acquired ImmunityNaturally-Acquired Immunity

There are two types of There are two types of naturally-acquired naturally-acquired immunity:immunity:

1.1. Active immunityActive immunity – this is – this is what happens when we what happens when we are randomly exposed to are randomly exposed to pathogens.pathogens.

2.2. Passive immunityPassive immunity – this is – this is when a mother transfers when a mother transfers her antibodies to her her antibodies to her fetus across the placentafetus across the placenta

Artificially-Acquired ImmunityArtificially-Acquired Immunity

There are two types of There are two types of artificially-acquired artificially-acquired immunity:immunity:

1.1. Active immunityActive immunity – the – the type of immunity that is type of immunity that is stimulated by stimulated by vaccination.vaccination.

2.2. Passive immunityPassive immunity – when – when antibodies are produced antibodies are produced elsewhere, and injected elsewhere, and injected into a bodyinto a body

AntibodiesAntibodies

Antibodies are proteins that Antibodies are proteins that are made by the body in are made by the body in response to a specific response to a specific pathogen. Different pathogen. Different pathogens cause our bodies pathogens cause our bodies to produce different to produce different antibodies.antibodies.

Once antibodies are produced, Once antibodies are produced, they remain in our bodies they remain in our bodies for a long time, so that if we for a long time, so that if we encounter the same encounter the same pathogen again, we are pathogen again, we are protected.protected.

Question???Question???

If antibodies remain in If antibodies remain in our bodies for a long our bodies for a long time, how come we get time, how come we get the common cold over the common cold over and over? Why arenand over? Why aren’’t t the antibodies the antibodies protecting us when we protecting us when we get it again?get it again?

AntigensAntigens

An antigen is any An antigen is any substance that is substance that is foreign that gets foreign that gets into our bodies and into our bodies and stimulates our stimulates our immune system. immune system. Ex: bacteria, Ex: bacteria, viruses, pollen, viruses, pollen, dust, etc.dust, etc.

Immune System DualityImmune System Duality

The immune system consists of The immune system consists of two major mechanisms:two major mechanisms:

1.1. Humoral ImmunityHumoral Immunity – involves – involves B cells (wbcB cells (wbc’’s) which produce s) which produce antibodies against free-antibodies against free-floating pathogensfloating pathogens

2.2. Cell-Mediated ImmunityCell-Mediated Immunity – – involves T cells (wbcinvolves T cells (wbc’’s) that s) that kill intracellular pathogens by kill intracellular pathogens by phagocytosisphagocytosis

Immune System DualityImmune System Duality

ImmunizationImmunization

Immunization is to make immune Immunization is to make immune by vaccination.by vaccination.

1.1. Herd immunity – when a Herd immunity – when a person is not vaccinated, but person is not vaccinated, but is protected because everyone is protected because everyone around them IS vaccinated.around them IS vaccinated.

2.2. See list of vaccine-preventable See list of vaccine-preventable diseases in your notes.diseases in your notes.

Vaccination SchedulesVaccination Schedules

Vaccination SchedulesVaccination Schedules

Vaccination SchedulesVaccination Schedules

Always remember…Always remember…

The End!The End!All this talk of

blood has made me very thirsty……..