Immunity Flashcards
Define nonsusceptibility, including what factors it is and is not dependent on.
absolute protection against particular diseases associated with species characteristics; dependent on inherited physiologic and anatomic factors (such as diet and body temperature), NOT dependent on detectable antibodies
Define natural resistance.
ability of the individual to resist infection by means of normally present body functions; these functions are all subject to influence by nutrition, age, fatigue, stress, and genetic determinants
What are the two kinds of natural resistance and what are they composed of?
external (lactic acid in body secretions, cilia motion, urine excretion, stomach acid, lysozyme in tears and saliva, normal flora) and internal (cellular and humoral immunity, phagocytosis, inflammation)
What cellular mechanism are both natural and acquired immunity dependent on?
phagocytosis
What are the four basic steps in the phagocytic cycle?
physical contact between white cell and foreign particle -> formation of phagosome -> formation of phagolysosome -> digestion and release
What are opsonins?
serum proteins that attach to foreign substances and help prepare them for phagocytosis
What are the three important opsonin categories?
c-reactive proteins (CRP), complement components, and antibodies
What characteristic of phagocytic cells aids them in making contact with and initiating digestion of foreign particles?
they have receptors for immunoglobulins and complement components
By what process is undigested material excreted from a phagocytic cell?
exocytosis
Define phagocytosis.
an oxygen-dependent process by which a white cell kills and ingests foreign cells or particles
What substance is phagocytosis dependent on, and what does the process create to irreversibly damage the proteins of foreign particles?
oxygen-dependent; creates hypochlorite and hydroxyl ions
What three kinds of white cells fall under the category of granulocytes?
neutrophils, basophils, eosinophils
How do neutrophils move to areas of tissue damage in the inflammation process, and what is this mechanism called?
capable of moving from the circulating blood to the surrounding tissues by permeating the blood vessel walls (called diapedesis)
What are chemotaxins? Name these substances.
chemical messengers that cause migration of cells in a particular direction - these include complement components; coagulation cascade proteins; bacterial and viral products; and cellular secretions from mast cells, lymphocytes, macrophages, and neutrophils
What is chemotaxis?
process in which cells tend to move in a certain direction under the stimulation of chemotaxins
What is the most important role of eosinophils?
neutralizing basophil and mast cell products, and killing certain parasites
What substance is found in the granules of basophils and mast cells that, when released, cause hypersensitivity symptoms?
histamine
What type of white cell differentiates in the tissue to become a macrophage, and how long does it remain in the circulation before this differentiation takes place?
monocyte; ~70 hrs
What cell is the most active of all phagocytic cells?
macrophage
What are the six functions of macrophages?
microbial killing; tumoricidal activity; killing of intracellular parasites; phagocytosis; cell mediator secretion; antigen presentation
What are mast cells?
connective tissue cells of mesenchymal origin that resemble basophils, though they are larger, with a small round nucleus and more granules; widely distributed throughout the body with a lifespan of 9-18 months; participate in hypersensitivity reactions by binding IgE
What are dendritic cells?
cells covered with long membranous extensions - resemble nerve cell dendrites; mainly phagocytose antigen and present it to T-helpers; called “Langerhans” on skin and mucus membranes, “interstitial” in major organs; most potent phagocytic cell in tissue