chapter 43: the immune system Flashcards
What are pathogens?
agents that cause disease, infect a wide range of animals including humans
What is the main function of the immune system?
recognizes foreign bodies and responds with the production of immune cells and proteins
What is innate immunity?
a defense active immediately upon infections
What is adaptive immunity?
involves specific recognition
acquired immunity develops after exposure to agents such as microbes, toxins and foreign substances
What is the innate immunity in invertebrates?
- exoskeleton is made of chitin and is first barrier to pathogens
- digestive system is protected by chitin-based barrier and lysozyme
- hemocytes carry out phagocytosis
What is phagocytosis?
the ingestion and digestion of foreign substances including bacteria
What are the innate defenses in vertebrates?
- barrier defesnses
- phagocytosis
- antimicorbial peptides
- natural killer cells
- interferons
- inflammatory response
What is the mechanism of barrier defenses?
includes skin and mucous membranes of respiratory, urinary and reproductive tracts
What is the cellular innate defenses mechanism?
- phagocytic cells recognize groups of pathogens by TLRs, Toll-like receptors.
- TLRs recognize fragments of molecules characteristics of a set of pathogens
- white blood cells engulf invading pathogens, creating vacuole
What are the four main types of phagocytic cells?
- neutrophils: engulf and destroy pathogens
- macorphages: found throughout body
- dendritic cells: stimulate development of adaptive immunity
- eosinophils: release destructive enzymes
What is the function of natural killer cells?
they circulate through the body and detect abnormal cells. they then release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells
What is the role of interferon?
provides innate defense, interfering with viruses and helping activate macrophages
What is the inflammatory response?
- is brought about molecules released upon injury or infection
- mast cells release histamine, triggering blood vessels to dilate and become permeable - macrophages release cytokines, inhancing immune response. blood flows to site helps deliver antimicrobial peptides, accumulating pus.
What is the use of a fever?
systematic inflammatory response triggered by substances released by macrophages in response to pathogens
What are the two different types of lymphocytes?
1, T cells: lymphocytes mature in thymus
2. B cells: lymphocytes mature in bone marrow
What are antigens?
substances that can elicit a response from B cell or T cell
How do T and B cells bind antigen?
Via antigen receptors
small acessible part of an antigen that binds to antigen receptor called epitope
What does antigen recognition by B cells cause
gives rise to cells that secrete a soluble form of the receptor called antibody or immunoglobulin
How does antigen recognition by T cells work?
- t cell binds to antigen fragments
- antigen fragments are bound to cell-surface proteins called MHC molecules they are host proteins
- MHC molecules bind and transport antigen fragments to cell surface (antigen presentation)
what is the mechanism of proliferation for B cells and T cells?
- once activated B/T undergoes multiple cell divisions (clonal selection) to produce a clone of identical cells
- binding of a mature lymphocyte to an antigen initiates events that activate lymphocyte
What are the two types of clones produced?
- short-lived activated effector cells that act immediately.
- long lived memory cells that can give rise to effector cells if the same antigen is encountered again
What is immunological memory?
is responsible for long-term protections against diseases due to a prior infection or vaccination
What happens after first exposure to specific antigen?
- primary immune response
selected B and T cells give rise to their effector forms - in secondary response, memory cells facilitate a faster, more efficient response
What is the humoral immune response?
antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
What is cell-mediated immune response
specialized T cells destroy affected host
How do helper T cells respond to antigens?
- class II MHC molecules are the basis upon which antigen-presenting cells are recognized
- antigen receptors on surface of helper T cells bind to the antigen and the class II MHC molecule (signals exchange between the two cells)
- the helper T cells is activated, proliferates and forms clone of helper t cells
How are the B cells activated?
- in response to cytokines, a B cell proliferates and differentiates into memory B cells and plasma cells
- activated B cells give rise to thousands of plasma cells
- they produce and secrete antibodies
- antigens recognized by B cells contain multiple epitopes
What are the different functions of antibodies?
- they mark pathogens for destruction
- neutralization: they bind viral surface proteins preventing infection
- opsonization: they bind to antigens on bacteria, triggering phagocytosis
- antigen-antibody complex can bind to complement protein, triggering cascade of complement protein activation
What are cytotoxic T cells?
- effector cells in the cell-mediated immune response
- they kill cells infected by viruses or other intracellular pathogens
- they secrete proteins that disrupt the membranes of target cells and triggers apoptosis
What is immunization?
use of antigens artificially introduced into the body to generate an adaptive immune response and memory cell formation
What is active immunity?
develops naturally when a pathogen invades the body and elicits a primary or secondary immune response
What is passive immunity?
provides immediate, short-term protection
What are allergies?
exaggerated responses to antigens called allergens
What is not part of the insect immunity?
activation of natural killer cells
An epitope associates with which part of an antigen receptor or antibody?
variable regions of a heavy chain and light chain combined
Can a lymphocyte have receptors or multiple different antigens?
no
What does vaccination increase?
lymphocytes with receptors that can bind to the pathogen
What does not help a virus avoid triggering an adaptive immune response?
producing proteins very similar to those of other viruses
