A&P 21: The Immune System - Innate & Adaptive Body Defenses Flashcards
Immunity
resistance to disease
Innate (nonspecific) defense system
system that responds within minutes to protect the body from all foreign substances
Adaptive (specific) defense system
an “elite fighting force” equipped with high-tech weapons to attack particular foreign substances
Immune system
functional system (rather than an organ system) including a diverse array of molecules plus trillions of immune cells (esp lymphocytes) that inhabit lymphoid tissues and circulate in body fluids
Pathogens
harmful or disease-causing microorganisms
Neutrophils
most abundant type of WBC; become phagocytic on encountering infectious material in the tissues
Macrophages
most voracious phagocytes; “big eaters”; derive from WBC’s called monocytes
Monocytes
WBC’s that become macrophages upon leaving the bloodstream & entering the tissues
Phagosome
vesicle formed as a result of phagocytosis
Phagolysosome
phagosome + lysosome
Opsonins
complement proteins or antibodies that provide “handles” to which phagocyte receptors can bind
Opsonization
process of a pathogen becoming coated with opsonins (“to make tasty”); greatly accelerates phagocytosis of a pathogen
Respiratory burst
promotes killing of pathogens by liberating a deluge of highly destructive free radicals (including superoxide), producing oxidizing chemicals (H2O2 and a substance identical to household bleach), and increasing the phagolysosome’s pH and osmolarity, which activiates other protein-digesting enzymes that ingest the invader
Natural killer (NK) cells
“police” the body in blood and lymph; a unique group of defensive cells that can lyse and kill cancer cells and virus-infected body cells before the adaptive immune system is activated; “pit bulls” of the defense system; part of a small group of large granular lymphocytes
Inflammatory response
triggered whenever body tissues are injured by physical trauma, intense heat, irritating chemicals, or infection by viruses, fungi, or bacteria
Mast cells
key component of the inflammatory response; release the potent inflammatory chemical histamine
Histamine
potent inflammatory chemical released by mast cells
Toll-like receptors (TLRs)
surface membrane receptors; play a central role in triggering immune responses
Kinins, prostaglandins, and complement
inflammatory chemicals
Hyperemia
congestion with blood
Exudate
fluid containing clotting factors and antibodies
Leukocytosis-inducing factors
injured cells release these chemicals
Leukocytosis
increase in white blood cells, characteristic of inflammation
Margination
phenomenon of phagocytes clinging to the inner walls (margins) of the capillaries and postcapillary venules
Diapedesis
process of continued chemical signaling prompting the neutrophils to flatten and squeeze between the endothelial cells of the capillary walls
Chemotactic agents
inflammatory chemicals act as “homing devices”
Chemotaxis
neutrophils and other WBCs migrating up the gradient of chemotactic agents to the site of injury is a positive version of this
Pus
creamy yellow mixture of dead or dying neutrophils, broken-down tissue cells, and living and dead pathogens; may accumulate in a wound
Antimicrobial proteins
enhance our innate defenses by attacking microorganisms directly or by hindering their ability to reproduce; most important of these are interferons and complement proteins
Interferons (IFNs)
some infected cells can secrete these small proteins to help protect cells that have not yet been infected
Complement system (complement)
a group of at least 20 plasma proteins that normally circulate in the blood in an inactive state; include C1-C9, factors B, D, and P, and several regulatory proteins
Classical pathway
1 of 3 pathways by which complement can be activated; involves antibodies (water-soluble protein molecules that the adaptive immune system produces to fight off foreign invaders)
Lectin pathway
1 of 3 pathways by which complement can be activated; involves lectins (water-soluble protein molecules that the innate immune system produces to recognize foreign invaders)
Alternative pathway
1 of 3 pathways by which complement can be activated; triggered when spontaneously activated C3 and other complement factors interact on the surface of microorganisms
Membrane attack complex (MAC)
group of complement proteins, the insertion (into the cell membrane) of which is triggered by C3b binding to the target cell’s surface; forms and stabilizes a hole in the membrane that allows a massive influx of water, lysing the target cell
Fever
abnormally high body temperature; a systemic response to invading microorganisms
Pyrogens
“fire”; chemicals that act on the body’s thermostat (a cluster of neurons in the hypothalamus) - raising the body’s temperature above normal
Adaptive immune system
the body’s built in specific defense system that stalks and eliminates with nearly equal precision almost any type of pathogen that intrudes into the body
Humoral immunity
antibody-mediated immunity; provided by antibodies present in the body’s humors (fluids)
Cellular immunity
cell-mediated immunity; when lymphocytes rather than antibodies defend the body; has cellular targets
Antigens
substances that can mobilize the adaptive defenses and provoke an immune response; ultimate targets of all adaptive immune responses
Nonself
intruders into the body; antigens
Complete antigens
functions in immunocgenicity and reactivity
Immunogenicity
ability to stimulate specific lymphocytes to proliferate
Reactivity
ability to react with the activated lymphocytes and the antibodies released by immunogenic reactions
Hapten
incomplete antigen; troublesome small molecule; unless attached to protein carriers, they have reactivity but not immunogenicity; certain drugs (PCN), chemicals in poison ivy, animal dander, detergents, cosmetics, and a number of common household and industrial products act as these
Antigenic determinants
the parts of the antigen that are immunogenic
Self-antigens
assuming your immune system has been properly “programmed,” these are not foreign or antigenic to you, but are strongly antigenic to other individuals (basis of transfusion reactions and graft rejection)
MHC Proteins
group of glycoproteins among the cell surface proteins that identify a cell as self; each has a deep groove that holds a peptide (either a self-antigen or a foreign antigen)
Major Histocompatibility Complex (MHC)
codes for MHC proteins
B lymphocytes (B cells)
oversee humoral immunity