690520
Description
Flashcards by Stephen Cole, updated more than 1 year ago
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Created by Stephen Cole
about 10 years ago
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| Question | Answer |
| 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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