Chapter 32 And 33 Flashcards
Immune system function
The Immune System and the Lymphatic System work hand-in-hand. Specifically, the Immune System:
protects the body from pathogens
is made up of the Lymphatic System, specialized cells, and ‘free-floating’ molecules
Immune system defence
The immune system continuously monitors the body for ‘invaders’ and is ready to spring into action when necessary
Antigens
Antigens are unique identifying molecules recognized by the immune system. There are two main types:
Self antigens
on the surface of cells that are unique to an individual (e.g. antigens on an individual’s red blood cells)
Nonself antigens
On the surface of foreign cells (eg. Pathogens, organ transplants)
Self antigens have
Self-tolerance: The immune system attacks abnormal or foreign cells but leaves the body’s own cells alone
Non self antigens have ______ which is -________
Immunocompetence: the ability of the immune system to activate an effective response to a nonself antigen
Innate (non-specific) immunity
always present and ‘in place’
general defense against ‘nonself’ antigens
quick, initial response
Adaptive (specific) immunity
develops through exposure to ‘nonself’ antigens
response is specific, that is, unique to particular antigens
slower, developed response (especially if it is the body’s first exposure to the antigen)
Innate immunity and adpative immunity are
complementary strategies that work together to defend the body against ‘invaders’ of all types.
Examples of innate cells
Epithelial barrier cells (skin, mucosa) Phagocytic cells Neutrophils (most numerous pus) Monocytes become large phagocytes = macrophages Macrophages Kupffer’s cells (liver) Dust cells (lung) Natural Killer (NK cells) apoptosis (see Figure in Textbook)
Example of adaptive cells
Lymphocytes
B-cells
T-cells
Substances that contribute to immune response
Cytokines
Complement
Antibodies
Interferon
Cytokines
Chemicals released from cells to trigger or regulate immune responses
Examples include: interleukins (ILs), leukotrines, interferons (IFNs
Complement
A group of about 20 inactive enzymes (plasma proteins)
Produce a domino effect of reactions formation of a membrane attack complex (MAC)
End results is lysis of ‘foreign’ cell
Antibodies
a plasma protein made by B-lymphocytes (B cells) to destroy or inactive antigens
Interferon
a protein made by certain cells when they are invaded by a virus
interferes with virus replication
First line of defense
Innate
Skin/secretions
Mucosa
Tears, saliva, HCL
Second line of defence
Innate
Inflammation (heat, redness, swelling)
Phagocytosis
Third line of defence
Adaptive
Phagocytes
Specific immune response
Natural killer cells
Inflamatory response
A generalized response to pathogens that are causing tissue damage (signs = heat, redness, pain, swelling; fever)
Triggers release of immune factors from immune system cells
attracts WBCs
causes increased blood flow (site becomes warm and reddened) and increased vascular permeability (site swells with associated discomfort)
These changes help phagocytic WBCs reach the site and enter the affected tissue (See Figure in Textbook
Adaptive/specific immunity
Protection against invaders due to the ability of the body to recognize, respond to, and remember specific harmful substances or bacteria – aka nonself antigens.
Third line of defense
Antigen-specific ‘customized’ response
Response is systemic (not restricted to initial area of ‘invasion’)
Has memory - if the body is ever exposed to the same antigen, the immune response will be even stronger than it was to previous exposures
Involves B-lymphocytes (B cells) & T-lymphocytes (T cells
B and T cells
Both originate from immature hematopoietic cells in the red bone marrow
Once formed, both circulate to lymph nodes and spleen
T cells make a ‘pit-stop’ in the thymus as part of their development
Both become activated by exposure to antigens/chemical signals; however, they have very different immune mechanisms once activated!
B cell development
Activated B cells undergo repeated and rapid mitosis to form two different ‘cloned’ populations of cells:
Plasma cells - secrete antibodies into blood to form an ‘army’ of protection against an antigen (up to 2,000 antibody molecules per second!)
Memory cells - are stored in lymph nodes as an ‘emergency supply’ and then if subsequent exposure to the same antigen occurs, memory cells quickly become plasma cells and secrete antibodies
B cells
B cells
Do not directly attack antigens
Launch attack by making antibodies that either:
attack antigens; or
direct other cells to attack antigens
Referred to as:
Antibody-mediated immunity; or
Humoral immunity
Antibodies
Are types of immunoglobulins (Igs)
G, A, M, E, D (see Figure in Textbook)
IgG – most abundant circulating Ig (makes up 75% of all antibodies in the blood)
IgM –immature B-cells make it and insert it into their plasma membrane; most predominant one made after initial antigen contact
Protein compounds with specific combining sites
Combining sites attach antibodies to specific antigens, forming an antigen–antibody complex
Inactivation of antigens in this way is called humoral or antibody-mediated
Antibodies aka
Immunoglobins or lgs
Antigen
Antigen–antibody complexes have various modes of action. They may: Neutralize toxins Clump or agglutinate enemy cells Promote phagocytosis Complement fixation
Complement fixation
A group of about 20 inactive enzymes (plasma proteins)
Complement fixation
Important mechanism of action for antibodies
Causes cell lysis by permitting entry of sodium and then water through ‘holes’ (MACs = membrane attack complexes) created in the plasma membrane by complement molecules cell bursts due to an increase in internal osmotic pressure (cytolysis
T cells
Like B cells, T cells must be activated by an antigen; however note that T cells:
Don’t make antibodies
React to cells that are already infected or have engulfed antigen
Can only react to protein fragments on the surface of APCs or infected cells (recall antibodies made by B plasma cells can react to soluble antigens in blood plasma)
Carry out cell-to-cell ‘direct contact’ combat by:
Killing APCs or infected cells by ‘poisoning’ them
Releasing chemicals that attract and activate macrophages to destroy APCs and infected cells by phagocytosis
Referred to as:
cell-mediated immunity or cellular immunity
T cell development
Similar to a B cell, once a T cell is activated by/sensitized to an antigen, it forms two types of cloned populations of the original T-cell:
Effector T cells
Memory T cells
Memory T cells
Remain in red bone marrow until needed
Produce more active T cells if necessary
Effector T cells
Use ‘contact’ to kill APCs/infected cells
Release cytokines to orchestrate killing of APCs/infected cells, e.g.
Interleukins (ILs) are a class of cytokines involved in a wide variety of immune functions in different cell types
Lymphotoxins are powerful poisons that act more directly, quickly killing any cell it attacks
Cytotoxic T cells
aka ‘killer T cells’
Release lymphotoxins
Cause contact killing of a target cell (APC or infected cell)
Helper T cells and suppressor T cells
Help to regulate adaptive immunity by regulating B and T cells
Helper T cells
Secrete cytokines that stimulate B cells and cytotoxic T cells as well as phagocytes and other leukocytes
Activated TH form cloned populations of TH cells & memory TH cells
Suppressor T cells
aka or Regulator cells (T-regs)
Suppress B cell differentiation into plasma cells (allows fine tuning of antibody-mediated response)
Regulate other T cells, including reducing T-cell reactions to self-antigens ( self-tolerance autoimmune diseases, organ transplants)
Humoral immunity
Immunity conferred by the action of antibodies
Activated B cells plasma cells and memory cells
Cell- mediated immunity
Immunity conferred by the action of cells
Activated/Sensitized T cells kill APCs and infected cells directly by:
releasing toxins that kill APCs/infected cells
Releasing cytokines to attract and activate macrophages to kill APCs/infected cells by phagocytosis
Natural immuity
Exposure to pathogen is not deliberate
Artificial/ acquired immunity
Exposure to pathogen is deliberate
There are both _____ and _____ forms of natrual and artificial immunity
Active and passive
Natural immunity
Inherited immunity to certain diseases from birth
Exposure to pathogen is not deliberate
Can be active or passive
Active – active disease promotes immunity (production of antibodies)
Passive – mother passes immunity (antibodies) to fetus through placenta or breast milk
Artificial/ acquired immunity
Exposure to pathogen is deliberate (immunization)
Can be active or passive
Active – vaccination ‘stimulates’ antibody production leading to immunity (typically longer lasting)
Passive – immune ‘material’ (antibodies) developed in another individual is given to a non-immune person via an injection (typically shorter lasting)
