As Biology Chapter 6 Keywords

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Pathogen

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Any microorganism that causes disease.

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Immunity

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The means by which the body protects itself from infection.

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Non-specific mechanisms

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Does not distinguish between one type of pathogen and another, but responds to all of them in the same way. The mechanisms take two forms: a barrier to the entry of pathogens, and phagocytosis.

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Specific mechanisms

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Does distinguish between different pathogen. The responses are less rapid, but provide long-lasting immunity. The responses involve a white blood cell called a lymphocyte in two forms: T lymphocytes and B lymphocytes.

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Lymphocytes

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Types of white blood cell responsible for the immune response. They become activated in the presence of antigens.

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Phagocytosis

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Mechanisms by which cells engulf particles to form a vesicle or vacuole.

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Phagocytes

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A type of white blood cell that ingests and destroys pathogen in a process called phagocytosis.

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Phagosome

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A vesicle that engulfs the pathogen in phagocytosis.

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Histamine

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A chemical which causes dilation of the blood vessel.

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Antigens

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Any part of an organism or substance that is recognised as non-self (foreign) by the immune system and stimulates an immune response.

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B Lymphocytes (B cells)

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Associated with humoral immunity.

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T Lymphocytes (T cells)

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Associated with cell-mediated immunity.

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Cell-mediated immunity

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T lymphocytes will only respond to antigens that are attached to a body cell. T lymphocytes respond to an organisms own cells that have been invaded by non-self material.

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Antigen-presenting cells

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Cells that can present antigens of other cells on their own cell-surface membrane.

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Humoral immunity

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Immunity that involves antibodies or B cells that respond to one specific antigen when it enters the blood or tissue fluid. B cells will divide by mitosis in order to create clones which produce an antibody specific to the foreign antigen.

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Plasma cells

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A type of cell that secretes antibodies directly, which destroys the pathogen and any toxins it produces. They are a part of the primary immune response.

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Primary immune response

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The first response, by the immune system, to an infection.

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Memory cells

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These cells live considerably longer than plasma cells. These cells do not produce antibodies directly, but circulate in the blood and tissue fluid. They divide rapidly to make more plasma and memory cells if the same antigen appears again.

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Secondary immune response

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The second response, by the immune system, to future infections.

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Mitosis

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The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cells.

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Antigenic variability

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When antigens of viruses are constantly changing.

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Antibodies

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A protein produced by lymphocytes in response to the presence of the appropriate antigen.

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Heavy chains

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The polypeptide chains on antibody's which are long

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Light chains

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The polypeptide chains on antibody's which are short.

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Antigen-antibody complex

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When antigens fit into the antibody binding site.

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Variable regoin

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The binding site is different on different antibodies and so is considered variable.

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Constant region

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The rest of the antibody is the same in all antibodies and so is considered constant.

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Monoclonal antibodies

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When a single type of antibody is isolated and cloned.

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Polyclonal antibodies

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When clones each produce different antibodies as a cellective.

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Immunoassay

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The method of calculating the amount of a substance in a mixture. It is used in pregnancy testing kits.

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Vaccination

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The introduction of a substance into the body with the intention of stimulating active immunity against a particular disease.

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Passive

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Immunity produced by the introduction of antibodies into individuals from an outside source. This immunity is short-lived.

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Active

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Immunity produced by stimulating the production of antibodies by the individuals' own immune system. It is generally long-lasting.

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Herd immunity

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When a vast majority (all, if possible) of the vunerable population is vaccinated.