Immunology

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When a pathogen invades there are 2 types of responses:

1. Non-specific Response

- Barrier Mechanisms: mucus and skin.

- Other; phagocytosis, lysozymes, hydrochloric acid in stomach.

2. Specific Response

- All mediated immunity and humoral immunity

Non-specific reponse is a response that is that same for all pathgoens.

Specific response is a reponse that works only for one type of pathogen - one with a specific antigen.

Immune response - this is the ability to recoginise an antigen as foreign and and eliminate it.

Pathogen: this is a bacteria, virus, fungi or any other microogranism that causes disease

Pathogens will cause disease by:

1. Damaging the host cells.

2. Producing toxins.

Antigen: this is a protein or glycopritein that triggers an immune repsonse and antibody production.

Antigens can come in different forms:

1. As a free molecule such as a toxin

2. on the cell surface of the pathogen.

3. on cell surface of cell from other organisms from the same species.

4. abnormal body cell's cell surface

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Phagocytosis (non-sepcific response)

Phagocytes are a type of white blood cell, and there are 2 types of phagocytes:

1. Macrophages: large phagoyctic cells

2. Neutrophils: smaller than macrophages and they have a similar function, but the body produces many of them.

The Stages that occur during Phagocytosis

1. The phagocytes detect the foreign antigen and are attracted to it.

2. the phagocytes will engulf the pathogen and enclose its membrane around it, it will then trap it in the vacuole of the phagocyte.

3. The lysosomes which are in the cytoplasm of the phaguocyte will then fuse with vacuole and it will release lysozymes.

4. The lysozymes will kill the patogen by digesting/hydrolysing the pathogen.

5. the products of digestion such as amino acids are then absorbed back by the phagocyte.

Usually when a Macrophage carries out phagocytosis it will present the antigen on its cell and it becomes an antinge-presenting cell this cell will then trigger the specific immune response.

Lymphocytes

Those are also a type of white blood cells and there are 2 main types of lymphocytes:

1. B lymphocytes - produce antibodies. humonral response. mature in bone marrow.

2. T lymphocytes - mature in thymus. cellular response. attack patogens directly or can destroy infected body cells. do not secrete antibodies.

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Antibodies

- Those are proteins, they have a quternary structure because they are made up of 4 polypeptide chains.

- They have 2 variable regions so 2 antigens with the complementary shape receptors can bind at once.

- When the antigne and antibody bind they form an anting - antibody complex.

-The formation of an antigen-antibody complex is the first stage in the destruction of a cell carrying a non-self antigen.

The antibodies dont actually kill the pathogen themselves they prepare for destruction in 2 ways:

1. Agglutination; each antibody can bind to up to 2 anitgens, and therefore they form a clump and this makes the pathogen less spread out in the body and easier to locate by the phagocytes.

2. Markers; one the anitngen binds to the antiboduy to fomr an antigen anitbody complex it acts as a marker. This attracts the phagocytic cells to come and destroy the pathogen by hydrolysing it.

Helper T cells have protein recepotors on their cell surface membrane. the helper t cell with the complementary shaped receptor to antigen on the antigen presenting cell will attach to the antigen. this activates the helper t cells.

Helper t cells release chemicals called cytokines which activates cytotoxic T cells, produces memory cells, further phagocytosis and causes b cells to mature into plasma cells to secrete antiboides.