Microbiology- Chapter 15 (Specific Defenses Of The Host

Front 1

What is specific immunity?

Back 1

Specific Immunity

-When the non-specific defense fails, then the third, specific line of immunity is activated

-Immunity is not innate but adaptive; it is acquired over time
-It is characterized with a specificity and memory

-Specificity – antibodies against chickenpox is not effective against measles virus
-During the 2nd encounter with a pathogen, the lymphocytes recall the 1st engagement and attacks it again

Front 2

What is immunity?

Back 2

immunity is a defensive responses of the body when a foreign organism or foreign substance invades it

Front 3

What are antigens and antibodies?

Back 3

-Antigens are substances (proteins or polysaccharides) that provoke immune response
-Antibodies are proteins produced to inactivate the antigens

-During the immune response, lymphocytes organize and bind to the antigen

Front 4

What are the two components of the immune system?

Back 4

-Humoral immunity – production of antibodies (B-cells)

-Cell-mediated immunity – activation and proliferation of immune system cells (T-cells)

Front 5

What are the 5 stages of lymphocyte development and interaction?

Back 5

There are 5 stages:

1. Development of B-cells and T-Cells
2. Antigen presenting cells present the antigen to lymphocytes
3. Lymphocytes proliferate – produce responder cells and memory cells
4. B lymphocytes become plasma cells – produce antibodies
5. Activated T-cells become Helper T cells and cytotoxic T cells

Front 6

Describe the Specificity of the lymphocytes.

Back 6

-They have receptor sites on the cell surface that can recognize millions of different antigens
-This great diversity of receptor sites is achieved through genetic recombination of 500 genes
-The lymphocytes with the receptor sites for “self” cells are eliminated
-Upon entry of an antigen, only lymphocytes specific to that antigen proliferate – clonal selection

Front 7

What are the characteristics of antigens?

Back 7

Not a normal constituent of the body

-They are components of microbial cells (capsule, cell wall, flagella, fimbriae, microbial toxins, and coats of viruses), humans, plants, animals
-They belong to: proteins, lipoproteins, glycoproteins
-Good antigens have complex molecules
-Poor antigens have small and simple molecules



-Antigens contain specific regions that are recognized by antibodies – antigenic determinants or epitopes

Front 8

What are superantigens?

Back 8

-Superantigens (bacterial toxins) can trigger a 100 times greater response of immune system – toxic shock syndrome

Front 9

How are antigents processed ans presented?

Back 9

-Antigens are presented to lymphocytes by antigen- presenting cells (APCs) – macrophages, B cells, dendritic cells
-APC ingests the bacterial cell – degrade the antigen into smaller peptides
-Complexed with a cell glycoprotein (MHCII) and transported to the cell surface

-MHCII (major histocompatibility complex) – function in a recognition of self
-The antigen complexed with MNCII is presented to T helper cells
-T cells are activated – they release interleukin-2
-Assists with B cell system

Front 10

What stimulates the B-cells?

Back 10

-The linked receptor of T-cells and B-cells, and chemical stimulus from the T-cell – stimulates the B-cells

Front 11

What two types of cells are formed in B-cell activation and antibody synthesis?

Back 11

-Two types of cells are formed: memory cells and plasma cells

-Memory cells play role in future exposure to the same antigen
-Plasma cells – synthesize and release the antibodies

Front 12

what are antibodies?

Back 12

-Antibodies are specific proteins (immunoglobulins – lg) developed by the body that is invaded by a specific microorganism

Front 13

what is the structure of an antibody?

Back 13

-The antibody molecule is Y-shaped. It consists of 4 protein chains:

- 2 identical heavy chains
- 2 identical light chains
-Each antibody molecule has two binding sites (site that binds to antigen)

-Antibody molecule is made up of
-constant region
-variable region: binds the epitope of the antigen

Front 14

How do antibodies and antigens interact?

Back 14

Antibody-Antigen Interactions

-Complementary fit between antigen and antibody is needed
-The better the fit the better the stimulation of lymphocytes

Front 15

How are antigens rendered harmless?

Back 15

-Antigens are rendered harmless by different mechanisms

-Agglutination – antibodies cross-link the antigens (bacterial cells) forming aggregates that are more easily digested by phagocytes

-Opsonization- antibodies coat the antigens enhancing the phagocytosis

-Neutralization – antibodies block the active sites of viruses preventing their attachment to host cells

Front 16

What are the 5 immuoglobulin classes?

Back 16

IgG- 80% of all antibodies; effect against bacteria, toxin, trigger the complement system, long term immunity
-IgA- abundant in mucus membrane
-IgM- Large molecule, first to appear, circulate in blood
-IgD – small amounts (1%) has no well-defined function, B-cell activation
-IgE- play role in allergic reaction

*IGAMED*

Front 17

what is the primary response to antigens?

Back 17

Primary response
-There s a latent period
-Takes longer to reach the maximum

Front 18

What is the secondary respond to antigens

Back 18

Secondary response

-Memory cells responsible
-Fast response
-Higher concentration of immunoglobulins
-Basis for vaccination

Front 19

What are T-cells?

Back 19

-Produced in the bone marrow, mature in the thymus gland, and wait for the encounter with antigens in the lymphoid organs

Two populations of T-cells:

-Helper T-cells (with CD4 receptor)
-Recognize peptides that are presented on dendritic cells

-Cytotoxic T cells

Front 20

What are the helper t cells?

Back 20

-Activation helper cells produce cytokins – Th cells proliferate and produce
-Cytotoxic T cells
-natural killer cells
-macrophages
-Depression of T cell (class CD4) by HIV is responsible for pathology of AIDS

Front 21

What are cytotoxic t cells?

Back 21

Cytotoxic T Cells
-Recognize and kill the infected cell (some microorganisms multiple inside the host ell)
-Recognizes and kill nonself (tumor) cells
-Attaches to the target and releases perforin (pore-forming protein)

Front 22

what are natural killers cells?

Back 22

Natural Killer Cells

-Lymphocytes related to T cells
-They do not have specificity for antigen
-The first to attack cancer cells and virus infected cells

Front 23

What are the types of specfic immunity?

Back 23

Natural active immunity
-Getting the infection

-Natural passive immunity
-Maternal antibodies are transported across placenta

-Artificial Active Immunity
-Vaccination

-Artificial Passive Immunity (immunotherapy)
-Administration of specific antibody-obtained by vaccinating animals and extracting the serum

Front 24

What is the technique of Monoclonal Antibodies?

Back 24

-Technique by which large amounts of specific antibodies can be produced

Front 25

What are vaccines?

Back 25

-Vaccine is a suspension of microorganisms or their cell components that are injected into a human or animal body in order to induce immunity
-The purpose of vaccination is to control microbial diseases and to prevent epidemics

Front 26

what are the types of vaccines?

Back 26

Attenuated whole agent vaccine
-Use of living but attenuated (weakened) or mutant microbe. Measles, mumps, rubella (MMR)
-Advantage: more closely mimic an actual infection
-Disadvantage: can backmutate to virulent form and cause a disease

Inactivated whole-agent vaccines
-Use of killed microbes (rabies, influenza, and polio)
-Killed by formalin or phenol


Toxoids
-Chemically or thermally modified toxins used to stimulate active immunity
-Tetanus, diphtheria toxoids – requires series of injections
-Require boosters every 10 years

Front 27

What are recombinant vaccines?

Back 27

-Genetically engineered microorganisms produce the antigenic fraction of the pathogen (Hepatitis B).

Front 28

What is DNA vaccine?

Back 28

Promising technology in vaccine production
-Gene coding for an antigen is incorporated into a plasmid – “naked” DNA (plasmid) injected
-Human cells will take up the plasmid
-Foreign protein (antigen) will be expressed, this will stimulate immune response

Front 29

Why are vaccinations important?

Back 29

-To protect individuals
-To establish herd immunity
-Protection of the whole population
-Prevention of epidemics
-Protection of non-immunized individuals