Immune System Flashcards
First line of Defense
Non-specific way of preventing invaders from entering the body
Skin
Physical barrier
pH 3-5 due to oily secretions
Antimicrobial Proteins
i.e. Lysozymes that break down cell walls in bacteria
Fond in saliva, sweat, tears
Cilia
Found in lungs
Sweep out harmful bacteria
Gastric Juice
Kills many microbes in stomach
Symbiotic Bacteria
In digestive tract and vagina
Outcompete other bacteria that could be harmful
Second Line of Defence
Non-specific way of defence
Phagocytes
Complement
Interferons
Inflammatory Response
Phagocytes
Cells that engulf harmful particles via phagocytosis
Leukocyte
WBC
Neutrophils
Monocytes (become macrphages)
Type of phagocyte
Natural Killer Cells
NKs
Type of phagocyte
Attack tumors or pathogen infected cells
Complement
Proteins that “complement” other defenses
Attract phagocytes where they are needed
Also promote cell lysis if the cell is a threat
Interferons
Cells that are infected by a virus secrete interferons to promote neighbouring cells to produce virus fighting proteins
Inflammatory Response
Series of non-specific events that occurs in response to a pathogen
Histamine—> Vasodilation—> Phagocytes—> Complements
Inflammatory Response-Histamine
Released by basophils (WBC)
Increases permeability of the capillaries to WBC to allow them to engage pathogens in infected tissues
Inflammatory Response-Vasodilation
Occurs in response to histamine
Results in increased blood supply to affected area, allows WTV to more easily access where they are needed
Causes redness, swelling, increased temperature during a fever
Inflammatory Response- Phagocytes
Attracted to the injured area to engulf pathogens
Inflammatory Response- Complements
Leave chemical gradients, allowing phagocytes to follow them to the infected area
Help phagocytes engulf pathogens
Stimulate basophils to release histamine
Assist in lysis of foreign cells when necessary
Third Line of Defense
Immune response- specific
Antigen
Molecules detected as foreign by the immune response
Lymphocytes
Major component of immune response
WBCs originating in bone marrow, spend most of their time in lymph nodes, thymus gland, and spleen
Lymphocytes- B Cells
Originate and mature in bone marrow
PM of B cells contain Ab
Once Ab on B cell binds its specific antigen, B cell proliferates into 2 types of daughter cells (Plasma and Memory)
Ab
Specific to a certain antigen
Constant region- same for Ab in the same class and species (recognized by receptors on some cells)
Variable region- responsible for recognizing antigen
Ab Bind Antigen
Inactivates antigen until it is phagocytosed by macrophage
Ab bind surface antigen of cell
Stimulates Complement protein to come and lyse cell
B-Cells (Plasma Cells)
Release Ab into bloodstream, allowing them to circulate throughout the body and bind to antigen
B-Cells (Memory Cells)
Keep their Ab bound to their membranes
Long lived after coming int contact with an antigen
Reason one can be immune to many diseases after a previous exposure
Lymphocytes- T Cells (Recognition)
Originate in bone marrow, but mature in thymus gland
Have antigen receptors on surface, but are not Ab
Receptors recognize foreign cells via MHC Marks (self vs. non-self)
T cells look for displays of mixture of self/non-self markers on a self (indicates cell infected by virus)
Cancerous/transplanted cells are recognized as foreign
T-Cell Division
T cell divides and produces 2 types of daughter cells
Cytotoxic/Killer T Cells- recognize and puncture foreign cells (lysis)
Helper T cells - stimulate proliferation of cytotoxic T cells and B cells
Clonal Selection
Antigen binds to B cell, or foreign cell binds to T cell, causing proliferation into identical daughter cells
Clonal selection= cell bound to antigen was “selected” for, and cells that are not bound will not divide
Cell Mediated Response
Uses T cells to respond to foreign cells or cells invaded by pathogens
T cells—> cytotoxic T cells (destroy foreign cells)
T cells—> helper t cells (bind to macrophages that have already engulfed pathogens, marking them for destruction)—> Interleukins (stimulate proliferation of T/b cells)
Humoral Response
Uses Ab to respond to antigens on pathogens in the blood or lymph
Process of B cell–> plasma cells (release Ab to bind antigens)
B cells—> memory cells (future immunity)
Also involves macrophages and helper T cells stimulating production of more b cells
Sometimes, antigen binding to b cell does not directly stimulate the production of additional b cells
Pathogen needs to be engulfed by macrophage first, then helper t cell can bind macrophage, release interleukin and stimulate b cell production
Passive Immunity
Passing Ab from a previously infected individual to someone else who is newly infected with the disease
Newborn infants protected (Ab pass from both placenta and breast milk)
