Normal Immunology Flashcards
Body’s first line of defense
- innate and non-specific
- anatomic barriers
- biochemical barriers
- born with
Body’s second line of defense
- non-specific and immediate
- inflammatory response
- born with
Body’s third line of defense
- specific and slow
- immune response
- acquired
Antigen definition
a substance that induces a specific immune response
Antigen info
- immunologically, most antigens are pathogens, parts or products of pathogens, or other foreign compounds
- most antigens are proteins, but some lipids, polysaccharides and nucleic acids can also be antigenic
pathogen
any virus, microorganism, or other substance causing disease
Forms of immunity
- innate immunity
- acquired immunity
innate immunity
- 1st and 2nd lines of defense
- genetically determined - no prior exposure involved; present at birth
- non-specific defense mechanisms
acquired immunity
- 3rd line of defense
- gained after birth; produced by the host of a donor
- specific protection against specific antigens
Innate immunity surface defenses
- physical barriers (skin)
- normal bacterial flora (yeast infections)
- chemical inhibitors (gastric acid)
- antimicrobial substances (sebum)
- lysozymes
Innate immunity mechanical removal
- slough skin
- tears
- mucus (mucociliary elevator)
- ciliary action
- coughing
- salivation
- urination
- defecation
- vomiting
Nonspecific resistance factors
- fever
- interferons
- complement
- lysozyme
- lactoferrin
- a-antitrypsin
fever
may inhibit some pathogens; speed up body’s metabolism
interferons
interfere with viral replication inside the cell
complement
an opsonin; makes phagocytosis easier
lysozyme
an enzyme that can destroy some foreign organisms
lactoferrin
binds iron & removes it (Iron is an essential bacterial nutrient)
a-antitrypsin
inhibits bacterial enzymes
acquired immunity types
- passive immunity
- actie immunity
- natural
- induced
passive immunity
- natural
- induced
- produced by transfer of antibodies from another person or source
- occurs in nature (colostrum - moms milk)
- occurs through medical intervention (needle involved, administer serum; tetanus antitoxin snake anti-venom)
Active immunity
- natural
- induced
- produced by antibodies that the person’s own body develops in response to antigens (immune response)
- occurs in nature (become sick)
- occurs through medical intervention (administer vaccine)
primary response
- takes about two weeks to develop peak antibody titers (# of antibodies)
- IgM and IgG levels do not remain elevated
Secondary response
- characterized by a very rapid increase in IgG titer, to levels much higher than those of the primary response
- remains elevated for an extended period
antigenic drift
- cross protection
- antigens mutate and change over time
- influenze mutates often
cross protection
- antibody which fits old antigen partially fits new antigen
- similar but not identical antigen
Goals of a good immune system
- specificity
- versatility
- memory
- tolerance
specificity - immune system
targets a particular antigen only
versatility - immune system
ability to differentiate among tens of thousands of antigens
memory - immune system
a second exposure is stronger and lasts longer
tolerance - immune system
does not respond to “self” antigens
Cells of the immune system
- lymphocytes: formed in the bone marrow from two different cell lines:
- B lymphocytes (B Cells): humoral/blood (or antibody mediated) immunity
- T lymphocytes (T cells): cell-mediated immunity
- identical in appearance but have different functions
B Lymphocytes & Humoral Immunity
when B cells encounter antigens, they are stimulated to become mature plasma cells that secrete specific antibodies
maturation of B cells
- B lymphocyte precursors are produced in bone marrow
- first step: become immunocompetent (B cell school) during migration through the “burial equivalent”
- second step: activation to become mature antigen-specific plasma cells
Activated B cells give rise to which two cell lines?
- memory B cells (2nd exposure stronger and faster)
- plasma cells (produce and secrete immunoglobulins (antibodies)
Immunoglobulin is the same as?
Antibody
Antibody structure
- 2 polypeptide chains in a “Y” shape
- one pair of heavy chains
- one pair of light chains
- each chain has a constant segment (base and 1st part of the Y) and a variable segment (tips of Y)
- antigen binding sites are located on the variable segments “lock and key”
- the constant sites are responsible for the biologic functions of the molecule
- interacts w/ complement cascade, chemical mediators of inflammation , other WBCs, etc.
5 Classes of immunoglobulins?
-IgG
-IgA
-IgM
-IgE
-IgD
(gamed)
IgG
- G I Joes
- 80-85% of circulating immunoglobulins
- responsible for most antibody functions (precipitation, agglutination, complement activation)
- major antibody in fetal blood
IgA
- predominant antibody in normal body secretions (such as mucus, tears, saliva and milk and they attack pathogens before they gain access to internal tissues)
- secretory piece may protect against enzymatic degradation
- A= first letter, milk is the first thing newborns have related to immune system
IgM
- M= military & first responders
- first antibody secreted after the arrival of an antigen (subsequently IgM levels decrease as IgG production accelerates)
- 10 theoretical antigenic binding sites (only half of them work)
IgE
- important in allergic responses
- attached to basophils and mast cells (same)
- important but don’t hang in blood (stay in tissues)
- when antigens bind to IgE, these cells release histamine and other chemical mediators of inflammation
- degranulates when antigen attaches
IgD
- found only on the surfaces of developing B cells (immunocompetance)
- plays a role in activating the B cell to produce antibodies
function of antibodies
- neutralize bacterial toxins
- antibody acts as an antitoxin
- antitoxin-toxin complexes removed by phagocytes
- neutralize viruses
- does virus circulate in the bloodstream?
- activate components of the inflammatory response
- opsonize bacteria
- opsonins make bacteria more susceptible to phagocytosis (call over phagocytes)
Opsonization
- opsonins are binding enhancers that make phagocytosis easier
- bacteria have a “slime” capsule
- both antigens and antibody complexes and macrophages are negatively charged (greased pig)
two most common opsonins
- complement
- antibodies (holds on to bacteria to trigger macrophage to get it)
T Lymphocytes & Cell-Mediated Immunity
- T cells account for 80% of all lymphocytes
- T cells recognize specific antigens, which they attack directly
- T cell precursors are formed in the bone marrow and then become immunocompetent after migrating through the thymus
- These T cells produce plasma membrane receptors that are antigen-specific
