Exam 3 Immunology Flashcards
Basic function of immune system
recognition and removal of non-self material
resist tissue damage due to infectious organisms
Innate immunity
general processes that destroy foreign materials
phagocytosis, gastric enzymes, skin barrier, immune paint
acquire immunity (specific immunity)
Exposure to a foreign agent and activation of lymphocytes (t-cells) and antibody production (B-cells)
Cell-mediated immunity
T-lymphocytes - directly does something to the microbes
Humoral immunity
B lymphocytes (creates antibodies that tag microbes for something else to destroy)
T and B cells live in
lymphoid tissues (lymph nodes, lymphoid patches in GI tracts, skin and circulatory system)
T and B cells “recognize” and are activated by
antigens on foreign/infectious agents
antigens
protein or polysaccharide molecules on the plasmalemma of normal cells and infectious agents
Natural Killer Cells (NK cells)
type of cytotoxic lymphocyte (characteristics similar to CTLs)
recognize damaged and infected cells (also believed to be responsible for identifying and killing tumors -cancer cells)
have membrane receptors that allow modulation of their activity; can stimulate or inhibit function through the action of these receptors
thought to evolve from t-cells as cells capable of directly affecting damaged self-cells
Main phagocytic cell of the immune system
macrophages
most invading organisms are first
phagocytized and partially digested by macrophages and dendritic cells
The antigenic products are
put on the macrophage cell membrane and presented to lymphocytes
Antigen presentation leads to
lymphocyte activation:
- B-cells make antibodies directed against antigen
- T-cells are activated to recognize antigen/microbe
Professional antigen presenting cells
maintain both Major histocompatibility complex class I and II (macrophages, dendritic cells - lymph node cells, and B-lymphocytes)
Non-professional APCs
typically only have MHC class I (endothelial cells -vessels, fibroblasts -CTs, Glial cells -CNS, Thymus cells - immune system organ, thyroid cells - endocrine organ)
Millions of differently exposed T and C lymphocytes are stored in the
lymph tissue
Each B cell forms
only one type of antibody
Each T cell is activated by
one single antigen and is responsive only to that antigen
One the lymphocyte is activated by its antigen
it is stimulated to proliferate and become active
Major Histocompatibility Complex (MHC)
Complex of proteins utilized by antigen presenting cells
Consist of several smaller proteins (human leukocyte antigen; HLAs) polymerized together into one MHC
Exist as two separate classes MHC class I and MHC class II
MHC I and MHC II are located
on different cells and provide different ways of stimulating immune responses
what is responsible for the variation in MHCs
different HLAs
Specific Alpha and beta chains comprise the HLAs
MCH I
Occur on nearly all cells and professional APCs
Present antigenic proteins to lymphocytes (phagocytosis of extracellular microbes, bacteria/viruses, and cellular debris, self proteins, are presented as antigens
MCH I presentation stimulates
activity of CTLs (cytotoxic T-lymphocytes)
Activates CTLs
produce and release perforin and degradative enzymes
Perforin
puts membrane channels into infected cells (virus)
Degradative enzymes
proteases - enter cell and stimulate cell lysis/apoptosis (bacteria)
MHC II
present on professional APCs only,
some non-professional APCs can express these MHCs
Antigen presentation stimulates activity of T-helper cells (CD4+)
Th1 Cells
assist action of cytotoxic cells through the release of stimulatory cytokines
Th2 cells
assist B-cell production of antiboies
Tfh cells
assist b-cell differentiation into plasma cells and antibody production
T-regulator cells
assist in controlling immune response by reducing activity of CTLs and B-Cells
Cytotoxic T Cells (CTLs)
Directly kill antigen or non-self cell by protein channel insertion
Helper T-Cells
Stimulate activity of Killer T-cells and plasma cells
Suppressor T-cells (t-regulatory cells)
reduce activity of T or B cells i.e. limit immune response
Memory T Cells
activated during initial exposure to antigens, can activate quickly with re-exposure to same antigen
Lymphokine-producing T-cell
produce lymphokines enhance activity or T, B cells, and Macrophages
Once antigen is presented, Immature T-cells..
become active to proliferate and differentiate into: memory T-cells (reservoir of sensitized T-cells for quick response to re-exposure to antigen), Cytotoxic T cells (active T-Cells that immediately and directly destroy foreign microbes and damaged cells), Helper T-Cells (assist cytotoxic t-cell activity, phagocytosis and Ab production)
How cytotoxic t-cells work
T-lymphocyte recognizes antigen
t-lymphocyte inserts protein channel into invading cell
sodium and then water influxes and causes lysis of the microbe
T-cell can also bind and stimulate apoptosis (regulated cell death) -virally infected cell
How memory T-cells work
Normal t-cells are activated by an antigen
some of the activated t-cells become t-memory cells and are “dormant”
dormant cells until another antigenic exposure occurs
T memory cells are spread
throughout the lymphoid tissues of the entire body
upon subsequent exposure to the same antigen,
activated memory t-cells are presented to fight the new infection
most numerous t-cell (75%)
helper T-cells (Th1, Th2, Tfh lymphocytes)
How helper T-cells work
stimulate growth and proliferation of cytotoxic T-cells and suppressor T-cells
Stimulate B-cell growth and differentiation and production of antibodies
Stimulate activity of the macrophage system (phagocytosis and antigen presentation)
How regulator T-cells (suppressor T-cells) work
suppress the function of both the cytotoxic and helper t-cells
prevent cytotoxic cells from causing excessive immune reactions that might damage the body’s own tissues (limit immune response to prevent auto-immune reactions to self-antigens)
Primary Humoral Immune Response: B-cells
Once presented with antigen
B-cells are stimulated to proliferate and become plasma cells (Th2 and Tfh lymphocytes assist in these processes)
Primary Humoral Immune Response: B-cells
Plasma cells produce…
antibodies directed against the antigen presented (also produce antibodies associated with allergic response IgE)
In Primary Humoral Immune Response: B-cells, antibodies circulate
in the blood and move to tissues to recognize their antigen of interest (also bound to some APCs to allow them to recognize antigen)
in Primary Humoral Immune Response: antibodies bind
a specific antigen; this binding stimulates killing of the micro-organism (by phagocytic cells)
Structure of antibodies
each antibody is specific for a particular antigen
allows for tight binding of antibody to the antigen
During the secondary humoral immune response, a few B-lymphocyte clones…
do not go on to form plasma cells, but instead form “memory B cells”
Memory B-cells
circulate through the body to populate all the lymphoid tissues
they remain dormant until activated by a new quantity of antigen (2nd exposure to the same antigen causes a much more rapid and potent antibody response = secondary response)
first or second exposure to antigen results in
primary response: requires approximately 1-2 weeks to completely respond with full antibody production (IgM, then IgG) –likely to become sick/react to antigen before body has enough time to build up enough antibodies to fight it off
Secondary response: (response to second exposure) begins rapidly and is more potent, full antibody production occurs in 1-2 days (IgG) - memory B-cells; antibodies are formed for many months and confer long-lasting immunity
IgG in primary immune response
IgG formed 2nd in primary immune response
IgG in secondary immune response
IgG formed 1st in secondary immune response
IgG are ____ antibodies
circulating (in blood)
75% of all antibodies
IgG
Antibodies directed against allergens
IgE
Antibodies “placed” on basophils and mast cells
IgE
Binding of allergen to IgE stimulates
release of secretory granules that initiate an allergy response
IgM
formed 1st during primary response; are short-lived in the system (days) and are replaced by IgG
IgA
Found in bodily secretions (tears, saliva); prevalent in respiratory tract and known as immune paint
generate immune response to pathogens that enter external orifices (i.e. immune paint of the respiratory tract)
IgD (0.2% of all antibodies)
Assist in B-cell differentiation into plasma cells
Antibodies (humoral immunity) have 3 mechanisms to destroy infectious agents
- direct cellular attack on the invader (similar to T-cells)
- Activation of the “complement system” of plasma proteins that stimulate phagocytosis
- Antibody bound to antigen signal phagocyte to engulf microbe = opsinization
Agglutination - opsinization
multiple large particles such as bacteria are bound together into a clump by antibodies
Antibodies mechanism of direct attach
agglutination - opsinization
precipitation
neutralization
lysis
Precipitation
molecular complex of antigens and antibodies becomes so large that it is rendered insoluble and precipitates
Neutralization
antibodies cover the toxic sites of the antigenic agent
Lysis
antibodies directly attack the cell membrane of the invading organism and cause the membrane to rupture
The complement system
a group of 20 proteins that circulate in the plasma
complement proteins exist as inactive enzymes
antibo
Antibody-antigen complex causes
a cascade of sequential reactions that activate the complement enzymes
complement activation results in
an “amplified” reaction directed against infectious agents
Complement proteins stimulate
protein channel insertion into the cell membrane of microbes resulting in lysis
Also stimulate an amplification of the immune system
(recruitment of WBCs to the area - macrophages, lymphocytes, granulocytes)
(and stimulation of basophil, neutrophil, and eosinophil release of granules that increase inflammation)
Lymphoid tissue are sites for
sites for B and T cells and macrophages
Lymphoid tissues are spread throughout the whole body to
allow easy circulation of immune cells and as areas to complete immune elimination of infection agents/cancer cells
Lymph nodes locations
spread throughout the body
Spleen location
Located near the L colic flexure
Examples of lymphoid tissue
lymph nodes, spleen, thymus, tonsils, peyer’s patches, lymphoid nodules
Where is the thymus located
in the superior mediastinum
Lymph nodes of the throat
tonsils
Peyer’s patches location
lymphoid patches within the walls of the GI tract
Lymphoid nodules location
lymphoid patches within the dermis
Afferent lymphatic (lymph nodes)
drains interstitial fluid and phagocytic cells from body (tissue fluid)
Efferent lymphatic (lymph nodes)
returns filtered lymph to blood via venous system
Primary nodule (lymph nodes)
contains T and B lymphocytes and macrophages
Function of the spleen
monitors blood for microorganism
Function of thymus
site of differentiation of T-cells from bone marrow
Function of tonsils
guard against infection agents in the throat
Function of peyer’s patches and lymphoid nodules
line the digestive tract (and skin) to neutralize micro-organisms in food or from the environment
Immediate response allergy (i.e. hay fever, pollen)
IgE antibodies are bound to basophils/mast cells
Upon IgE binding to allergen, mast cell/basophils are stimulated to release granules
Rapid degranulation creates:
increased vascular permeability, vasodilation
increase glandular secretions (mucus, tears)
delayed response allergy (i.e. poison ivy)
t-cells are “sensitized” to allergen and are stimulated to proliferate and become active (48-72 hours); once activated T-cells move into the tissue where the allergen is located
At the infection site, T-cells release cytotoxic substances that destroy allergens (good) but also cause tissue damage (bad)
Cellular and humoral immune function response to aging
Decline with increasing age
Antigen challenge results in ______ antibody response at 60-70 years old compared to 20-30 years old
50-80% LESS
By 45-50 years of age thymus is
5-15% of maximal size
by 60 years of age (thymus activity)
there is no significant thymus activity (minimal decline in circulating T-lymphocytes)
How do you determine if it is okay to exercise when you are sick?
“Neck check” - if symptoms are above the neck
-try to perform exercise at 1/2 intensity for 10 minutes, if symptoms abate - continue, if not - stop.
If symptoms are below the neck - hold exercise
Chronic exercise and immune function
Chronic exercise is directly responsible for improved immune function
Chronic training increase
plasma volume, hematocrit, hemoglobin count, and WBC function
Chronic exercise training is directly related to reduced risk of
certain cancers
Overtraining has been related to
suppressed immune function
Active immunity
exposure to attenuated or dead microbe that still have antigenic properties; stimulated production of antibodies and memory cells; process of normal immunizations
Passive immunity
transfusion of antibodies or T-cells from human or animal that has been sensitized to an antigen; provides temporary immunity (2-3 weeks)
