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The Immune system. Role: protect body against pathogens Pathogens; bacteria, bacterial toxin, viruses, parasites, and fungi. Outline. Anatomy of the Immune system Organization of the body’s defenses Humoral immunity Cell-mediated immunity Immune responses in Health and diseases. Outline.

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The immune system l.jpg
The Immune system

  • Role: protect body against pathogens

  • Pathogens; bacteria, bacterial toxin, viruses, parasites, and fungi.


Outline l.jpg
Outline

  • Anatomy of the Immune system

  • Organization of the body’s defenses

  • Humoral immunity

  • Cell-mediated immunity

  • Immune responses in Health and diseases


Outline3 l.jpg
Outline

  • Anatomy of the Immune system

  • Organization of the body’s defenses

  • Humoral immunity

  • Cell-mediated immunity

  • Immune responses in Health and diseases


Anatomy l.jpg

Leukocytes

- Phagocytes (phagocytosis): neutrophils, eosinophils, monocytes, macrophages, dendritic cells (skin)

- Lymphocytes: Bs and Ts, natural killer cells

- Mast cells

Lymphoid tissues

- primary lymphoid tissues (bone marrow and thymus)

- secondary lymphoid tissues

Anatomy


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Outline

  • Anatomy of the Immune system

  • Organization of the body’s defenses

  • Humoral immunity

  • Cell-mediated immunity

  • Immune responses in Health and diseases


Organization of the body s defenses l.jpg

Non-specific defenses: no need to decipher pathogen’s identiy. Always present in the body.

- Physical barriers

- Inflammation

- Interferons

- Natural cell killers (NK cells)

- Complement system

Specific defenses:Based onn recognition of the pathogen’s identity

Humoral immunity

Cell-mediated immunity

Organization of the body’s defenses


Non specific defenses l.jpg

Physical barriers identiy. Always present in the body.

- skin

- mucus

- stream of tears or urine

- Inflammation

Chemical barriers

pH (stomach, vagina)

enzymes (stomach, tears)

Interferons

Complement system

Non-specific defenses


Inflammation l.jpg
Inflammation identiy. Always present in the body.

Symptoms of inflammation:

  • Redness

  • heat

  • Swelling

  • - pain


Macrophage and phagocytosis l.jpg
Macrophage and phagocytosis identiy. Always present in the body.


Interferon l.jpg
Interferon identiy. Always present in the body.

  • Protein secreted by a cell currently infected by a virus

  • Interferon warns the neighboring cells of the impending viral infection

  • The neighboring cells synthesize proteins that will block the virus from hijacking the cell DNA replication machinery

    Animation:

    http://people.eku.edu/ritchisong/interferon2.gif


Complement system l.jpg

About 30 blood proteins identiy. Always present in the body.

They become activated either by direct contact with a pathogen or by contact with a bound antibody.

In an activated state, they form a complex which opens a hole in a pathogen’s cell membrane  bacterial lysis

Complement system also promotes inflammation

Complement system


Natural killer cells nk cells l.jpg

Cytotoxic T cells, lacking markers identiy. Always present in the body.

Able to recognize a wide range of pathogens without prior exposure

When recognition and binding occur, the NK cells destroy the pathogen through cell lysis

Natural Killer cells = NK cells


Specific immunity l.jpg

Specificity: based on shape recognition of cell surface antigens

Diversity: Any shape can be recognized by a B or T-lymphocytes and trigger an immune reaction

Memory: once a pathogen has activated the immune system, memory cells remain and will protect against a secondary infection

Self-tolerance: the immune system does not attack itself

Specific immunity


Specific immunity the players l.jpg

Macrophages (antigen presenting cell = APC): phagocytize pathogens and present antigens to helper-T lymphocytes

Helper-T lymphocytes: secrete lymphokines and activate B and killer T lymphocytes

B-lymphocytes: multiply and specialize into plasma cells  secrete antibodies

Killer-T lymphocytes: kill (through lysis) infected or cancerous cells

Specific immunity = the players


Outline16 l.jpg
Outline pathogens and present antigens to helper-T lymphocytes

  • Anatomy of the Immune system

  • Organization of the body’s defenses

  • Humoral immunity

  • Cell-mediated immunity

  • Immune responses in Health and diseases


Antibody mediated humoral immunity ami l.jpg

1- Macrophages phagocytize a pathogen and present an antigen to a matching helper-T cell

2- At the same time, some pathogens contact B-cells matching the pathogen’s antigens

The helper-T cells multiply, secrete lymphokines which stimulate the B-cells to multiply and specialize into plasma cells

The plasma cells secretes antibodies

Antibody-mediated (humoral) immunity = AMI


Slide18 l.jpg

Figure 23.7 to a matching helper-T cell


What are antibodies l.jpg

Structures formed by 4 proteins to a matching helper-T cell

Two main regions:

the upper region is highly variable and bind to a specific shape (the antigen)

The base region is constant for all antibodies  this region, when the antibody is bound to its antigen, activates the complement system

What are antibodies?


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Role of the antibodies to a matching helper-T cell


Types of antibodies l.jpg
Types of antibodies to a matching helper-T cell

  • Antibody = immunoglobulin = Ig

  • IgG Most abundant. mostly in blood, lymph. able to cross the placenta

  • IgA  Found in tears, milk, blood, lymph

  • IgM  First antibody to be secreted. found in blood, lymph. unable to

    cross placenta

  • IgD  Found in blood, lymph, on B cells

  • IgE Found on mast cells, basophils. involved in allergic reaction.


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First and second exposures to a pathogen to a matching helper-T cell


Clonal selection l.jpg

Once a T, B or killer lymphocytes have made contact with their specific antigen, they are triggered into action but they also divide and form a large amount of identical cells, called a clone.

Clonal selection


Clonal deletion l.jpg

How can the DNA in the nucleus codes for each type of antibody?

Since over a millions of different types are needed, how can the DNA in the nucleus code for each of them? There is clearly not enough DNA to accomplish that.

During embryogenesis, several genes coding for the variable portion of the antibody (and each responsible for part of a shape) reshuffle so each combination of genes codes for a specific antibody (and shape). So a stem cell receives the capability to form one single type of antibody.

Once formed, they circulate in the body. If they meet and bind to a shape (formed by a protein) present in the body, they are destroyed or deleted, so that only the stem cells responsible for antibodies aimed at foreign pathogens are left.

A stem cell able to react with our own proteins and not deleted during fetal life might later trigger an autoimmune disease.

Clonal deletion


Outline25 l.jpg
Outline antibody?

  • Anatomy of the Immune system

  • Organization of the body’s defenses

  • Humoral immunity

  • Cell-mediated immunity

  • Immune responses in Health and diseases


Cell mediated immunity l.jpg
Cell-mediated immunity antibody?

  • Similar reaction to AMI

  • The pathogen triggering the reaction is a virus infected cell or a cancerous cell.

  • Killer T lymphocytes are sensitized by contact and activated by lymphokines secreted by activated helper T lymphocytes


Slide27 l.jpg
CMI antibody?

Figure 23.11 (1 of 2)


Clinical applications l.jpg
Clinical applications antibody?

  • Immunization

    - Active and natural

    - Active and artificial

    - Passive and natural

    - Passive and artificial

  • Why are we vaccinating against some disease but not other?

  • Why not Ebola?


Clinical applications30 l.jpg

Immediate allergic reaction: due to IgE antibody?

Tissue transplant and tissue rejection: due to cytotoxic T cells

Clinical applications

Delayed allergic reaction:

due to cytotoxic T cells