immune system Flashcards
What are the roles of the following white blood cell types? neutrophils
- To kill micro-organisms, particularly bacteria. - To release *chemotactins that attract other neutrophils and macrophages - *Chemoattractant substances.
What are the roles of the following white blood cell types? lymphocytes
responsible for initiating an immune response when a foreign invader enters the body. The three primary lymphocyte types, including natural killer cells, B cells and T cells. Natural killer cells respond to antigens in a nonspecific way. B cells create antibodies unique to specific antigens. T cells initiate mediated immunity, a type of response where there are no antibodies. There are three different types of T cells and these include helper T cells, cytotoxic T cells and regulatory T cells.
What are the roles of the following white blood cell types? monocytes/macrophages
- monocytes defferentiated at the target tissue to macrophage - macrophage phagocytosis microbe, fuse with lysosome - macrophage display antigen on its surface as part of MHC class II molecule, that activate cytotoxic cell to kill the infected cell
What are the roles of the following white blood cell types? eosinophils
Eosinophilic functions include: movement to inflamed areas, trapping substances, killing cells, anti-parasitic and bactericidal activity, participating in immediate allergic reactions, and modulating inflammatory responses.
What are the roles of the following white blood cell types? basophils
basophil are responsible for a non-specific inflammatory reaction. - In response to a trigger (for example, an allergan) they release cytokines, molecular messengers which “oversee” some aspects of the inflammatory response. - With asthma and allergies, basophils in a sense “overreact” or react incorrectly, mounting an immune response when one is not needed. As noted above, when stimulated, basophils release histamine. Basophils are part of the innate immune system which means that they mount a non-specific attack (in contrast to the “specific attack” mounted by B cells as they produce antibodies against a very specific antigen.) For example, when stimulated by a real cause (such as a virus like smallpox) or “imagined” problem (such as a piece of pollen from a tree) they secrete histamine. This is the reason that antihistamines are often used for allergies.
cytotoxic T cell
– Cytotoxic T cells (CD8) directly attack foreign cells.
– The sensitised cytotoxic (CD8) T-cells will travel to the site where the antigen originally entered the body.
– The sensitised T-cells bind to antigens of the same kind that led to their formation.
– T-cells will bind to their specific antigen only if the antigen is presented by a macrophage.
– The antigen-bound sensitised T-cells then release
chemical messengers into the inflamed tissues called
cytokines.
helper T cell
– Helper T cells (CD4) stimulate B cells.
– Helper T cells do not directly kill infected cells.
– They “help” to activate
– cytotoxic T cells and macrophages to attack infected cells
– stimulate B cells to secrete antibodies
– Helper T cells become activated by interacting with antigen-presenting cells, such as macrophages.
– Suppressor T cells
– Suppressor T cells damp down the immune response.
T cell
– Each T-cell displays antigen receptors in its surface membrane.
– When an antigen(pre-processed and presentedby macrophages) encounters a T-cell whose surface receptors fit the antigen’s epitopes, the antigen binds to the T-cell’s receptors.
– This activates or sensitises the T-cell, causing it to divide repeatedly to form a clone of sensitised T-cells.
cytokine function
B cell
– B cells provide antibody- mediated (humoral) immunity.
– Fight bacterial infections.
– At a few months old,a human will have a mass of inactive B-cells.
B cell development
– Occurs when the inactivated B cells bind to a specific antigen causing the B cell to become activated.
– This antigen-antibody binding activates the B-cell triggering a rapid series of mitotic divisions.
– By dividing rapidly, a single B-cell produces clones some of which differentiate to become plasma cells and some that do not differentiate completely and remain in the lymphatic tissue as memory B cells.
plasma cell
– Plasma cells synthesize and secrete large amounts of antibody into the bloodstream.
– Antibodies produced by activated Plasma cells cannot cross the cell’s membrane.
– Instead ABs bind the pathogenic cells together.
memory cell
– MemoryB-cells donot secrete antibodies initially.
– If a memory cell is later exposed to the antigen that triggered
its formation it will become a plasma cell and secrete Ab.
how vaccine work and why booster required
A vaccine is a preparation of either:
– killed microorganisms,
– livingattenuatedorganisms,
– or living fully virulent organisms
that is administered to produce or artificially increase immunity to a particular disease e.g. chicken pox.
Booster Vaccinations
– If memory B & T cells do not encounter the antigen from a pathogen again after the initial sensitisation they may die – resulting in a loss of immunity.
– In young children, it may also take several vaccinations to achieve immunisation.
– Patients can be assessed for immunity e.g. immunity against rubella.
– If there is no or only slight immunity, a booster vaccination may be required.
compare and contrast active and passive immunity
