Immune System Flashcards
Immune system-
internal defense system against pathogens
pathogens
disease causing agents
Immune system- abilities
Ability to distinguish self from nonself; Ability to respond to danger signals from injured tissues
Three levels of defense:
Nonspecific first line of defense o Second line of defense (also nonspecific) o Third line of defense- the immune response
Leukocytes
- all white blood cells that come from stem cells in bone marrow; Secrete cytokines
cytokines-
signaling molecules
Neutrophils-
most abundant leukocytes, are phagocytes
Macrophages-
slower leukocytes, perform large amounts of phagocytosis
Dendritic cells-
alert immune system to antigens
antigens
foreign molecules
Basophils and mast cells
release enzymes and cytokines in response to antigens or injury
B and T lymphocytes-
help in the immune response
Natural Killer cells (NK cells)
help in second and third line of defense- kill mutated or infected body cells
see diagram
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Nonspecific first line of defense function
Function- general defense against all kinds of pathogens: Prevents pathogens from entering the body and quickly destroys those that do enter
Outer coverings-
part of first line of defense. skin, cuticles (plants), shells, chitin. Skin is covered with oily and acidic secretions from sweat glands which helps kill pathogens
Mucous membranes
part of first line of defense. Mucous membranes found in respiratory tract and reproductive tract. Mucous helps trap pathogens, Enzymes found in mucous helps destroy them
Enzymes such as lysozyme
part of first line of defense. found in tears and body fluids and breaks down cell wall of bacteria;
Gastric juice (acidic) of stomach
part of first line of defense. kills bacteria
Macrophage process
If a foreign organism passes through the first line of defense, a macrophage is generally the first to recognize. Engulfs the foreign cell; Releases cytokines- attract more macrophages and neutrophils; Releases complement proteins;
complement proteins
Bind to antigen and becomes activated; Positive feedback occurs- activates other types of complements, and so on; Activated complement proteins attract more phagocytic cells; Activated complement proteins also attack the cell wall or cell membrane of foreign bacteria and help lyse the cell
Inflammatory response
Cytokines and complements cause Inflammatory response, or inflammation- begins immediately after pathogen invasion or physical injury
mast cell
type of white blood cell
response to tissue damage
Mast cells respond to tissue damage by releasing histamine, causing warming and reddening of the skin. Histamine also causes increase in permeability of capillaries surrounding the infected tissue. Fluid and antibodies can leave circulation and enter the tissues. Edema occurs. Clotting factors leak out of capillaries to help heal damaged tissue
antibodies
unique antigen receptors. attach to and
mark/fight off foreign things
edema
fluid surrounding tissues increase, causing pain.
Histamine
- trigger vasodilation of arterioles in infected area (increase in diameter of blood vessels), causing warming and reddening of the skin.
What happens after clotting factors leak out of capillaries to help heal damaged tissue?
Phagocytic cells move from capillaries into infected area to engulf the pathogens. During phagocytosis, pyrogenic cytokines are released that raise the body’s temperature, causing fever. Fever helps increase enzyme activity, speeds metabolism, forms phagocytes quicker.
study second line of defense diagram
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Third line of defense- immune response–four features
Self/ nonself recongnition, Specificity, diversity, memory
Self/ nonself recongnition-
attack only foreign agents
Specificity-
attack specific foreign agents
diversity
cells have potential to respond to many different threats
Memory- r
some cells are set aside for future battle with that foreign agent
target third line of defense
`The immune response targets specific antigens- molecule, such as protein or polysaccharide, that can be identified as foreign
key defenders 3rd line
Major histocompatibility complex (MHC), Helper T cells, Cytotoxic (Killer) T cells, B cells
Major histocompatibility complex (MHC)-
glycoproteins which help immune system differentiate self from non self. Also called HLA in humans. Depends on 20 genes, each with around 50 alleles, therefore, no two people have same MHC proteins.
HLA
human leukocyte antigen complex
Cytotoxic (Killer) T cells
kill infected body cells
Helper T cells
bind to antigen-MHC complexes and secrete signals that call for production of B cells or T cells
B cells
recognize foreign antigens directly. Develop and mature in bone marrow. Each acquires antibodies before leaving bone marrow. Each B cell has more than 100,000 antigen receptors–Activated when meets antigen that it is programmed to detect
Antibody molecule
y shaped, Embedded in plasma membrane, Coded for by large gene which randomly selects different sections for transcription, producing billions of different varieties
immunoglobulins
5 classes of antibodies that are immunoglubulins, or Igs- IgA, IgD, IgE, IgG, IgM- have different functions
T cells
Developed in bone marrow, mature in thymus gland Also acquire TCRs. receptors recognize antigen-MHC complexes.
TCRs
T cell receptors. antigen receptors acquired by T cells.
antigen-MHC complex
MHC complexes of your own body cell if they have foreign antigen bits attached to them
clonal selection
Each B and T cell bears only one type of antigen receptor. Through clonal selection, antigen binds to only the B or T cell displaying the receptor specific for it. Descendants of activated cell form large population of genetically identical cells called a clone. Some become effector cells, which fight infection, while others become memory cells, which are held in body for years.
Where are antigens dealt with?
Antigens are captured and dealt with in lymph node.
Antibody-mediated (humoral) response
Responds directly to antigens or pathogens that are circulating in the lymph or blood.
first step of Antibody-mediated (humoral) response
APC (“Antigen Presenting Cell”), or dendritic cell ingests an antigen and presents an antigen-MHC complex
2nd step of Antibody-mediated (humoral) response
A helper T cell recognizes the antigen-MHC complex and proliferates, releasing cytokines that signal the b cells to divide
3rd step of Antibody-mediated (humoral) response
A B cell with the proper antibody recognizes the foreign antigen and is activated
4th step of Antibody-mediated (humoral) response
B cells produce effector, or plasma cells, which release antibodies that bind with antigens. prevents them from attaching to body tissues; also tags them for disposal by NK cells. B cells produce memory cells, which provide future immunity
Antibody-mediated (humoral) response diagram
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cell mediated diagram
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cell mediated diagram steps
Uses mostly T cells and responds to any nonself cell, including body cells invaded by pathogens (instead of circulating pathogens)
Antigen presenting cell ingest foreign antigen and displays an antigen MHC complex on the cell surface
T cells that recognize the antigen-MHC complex are activated and stimulated to make cytotoxic T cells and helper T cells
Helper T cells produce cytokines which stimulate a proliferation of helper T cells and cytotoxic T cells
Cytotoxic T cell can contact infected cell and touch-kill it by releasing perforins, which make holes in the infected cells plasma membrane
Active immunization-
vaccine, a substance that stimulates the production of memory cells, is taken into the body–either weakened or killed pathogens. Once memory cells are formed, live micoroorganisms will stimulate quick response by immune system.
Passive immunization-
injections of a purified antibody. Effects do not last- patient has no memory cells.
antibiotics
Antibiotics are chemicals derived from bacteria or fungi that are harmful to other microorganisms
invertebrates + plants
invertebrates have nonspecific response mechanisms but lack pathogen
specific defense responses
infections in plants trigger chemical responses that destroy infected and
adjacent cells thus localizing the effects
newborn infants
Newborn infants are protected through transfer of antibodies across the placenta and antibodies
in breast milk.
purpose of humoral response
deal with antigen
purpose of cell mediated response
deal with infected body cells
