Immunology flashcards

Frage	Antworten
Give two reasons why it is difficult to eradicate TB by vaccination.	=> Antigenic variability of bacterium => Vaccinated people may destroy the bacterium before antigens are produced => Mobile populations spread the disease
How are phagocytes attracted to a site of infection?	By chemoattractants secreted by pathogens.
How does the immune system detect invading pathogens?	Invaded cell or phagocyte presents antigens of pathogens; these are recognized by the T-helper cells with complementary receptor proteins
Name three natural defenses of the body to pathogens.	=> Mucous membranes => Hydrochloric acid => Skin acts as a barrier => Digestive enzymes => White blood cells
What type of white blood cells carry out phagocytosis of bacteria?	Macrophages
How may bacteria resist phagocytosis?	=> By having waxy cell walls which make digestion harder => By secreting chemicals which prevent phagocytes from being attracted
What four roles do activated T cells have?	=>Stimulating phagocytosis =>Producing interleukins which stimulate division of B cells by mitosis =>Specialising to cytotoxic T cells which kill infected cells by producing perforin =>Developing into memory cells for future infection
What four things must a microorganism do to be considered a pathogen?	=> Gain entry to a host. => Colonise a host tissue. => Resist host defenses. => Damage host cells.
What happens after a T-helper cell binds to an antigen-presenting cell?	The T-helper cell is activated and divides rapidly by mitosis.
What happens after the formation of a phagosome?	Phagosome fuses with a lysosome to form a phagolysosome, which contains enzymes to digest the pathogen
What is an antigen?	A molecule (usually a protein) which triggers an immune response
What is an antibody?	A protein produced by B lymphocytes in response to an infection.
What is an infection?	When a pathogen gains entry into a host and colonises a tissue.
What is formed when the cell membrane of a phagocyte fuses around a bacterium?	A phagosome.
What is perforin and how does it kill infected cells?	A protein released by cytotoxic T-cells which perforates the plasma membrane, causing it to become freely permeable to all substances, so that the cell dies.
What is the first step in humoral immunity?	The surface antigens of the invading pathogen are taken up by B cells.
What is the role of antibodies in immunity?	They bind to the complementary antigens of invading pathogens and either cause lysis or cause them to clump together (agglutination) so that they can be ingested by phagocytosis.
What is the role of memory cells in immunity?	Storing an immunological memory of the shape of the antigens of pathogens for future infection by the same pathogen
What is the role of plasma cells in immunity?	Producing antibodies complementary to the antigens of invading pathogens.
What two types of cell do B cells differentiate into?	Plasma cells and memory cells.
Where do B lymphocytes develop?	Bone marrow.
Where do T lymphocytes develop?	Thymus gland.

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