chap 16 pt. 1

immunology

the scientific study of the immune system and immune responses

primary functions of the immune system

differentiate between “self” and “non-self” and destroy that which is “non-self”

Cells invovled in immune responses originate in bone marrow

• 3 lines of lymphocytes derived from lymphoid stem cells of bone marrow

• 2 categories of T cells

3 lymphocyte types

B lymphocytes (b cells)

T lymphocytes (T cells)

Natural Killer cells (NK cells)

2 categories of T cells

helper T cells and Cytotoxic cells

2 major arms of the immune system

humoral immunity and cell mediated immunity

humoral immunity

special glycoproteins called antibodies (ab’s) are produced by B cells to destroy specific microbes

Cell mediated immunity

involves a variety of cell types (t cells, NK cells), with Ab’s only playing a minor role if any

Acquired immunity

immunity that results from the active production or receipt of antibodies during ones lifetime

Active acquired immunity

• antibodies are produced within the person

• usually provides long-lasting protection

passive acquired immunity

• antibodies are received that were produced by another person or persons or by an animal

• usually provides only temporary protection

2 types of active acquired immunity

natural active acquired immunity - occurs naturally

artificial active acquired immunity - artificially induced

a vaccine

material that can artificially induce immunity to an infectious disease, usually following injection or ingestion of a vaccine

What are most vaccines made from?

living or dead pathogens or the toxins they produce

How do vaccines work

by teaching your immune system to recognize and remember bacteria or viruses

Antigens

the memory of the foreign ingredients your body makes when you get a vaccine

How do vaccines help for the future

if in the future you are exposed to the actual disease, your immune system can then fight and kill the bacteria or viruses much more quickly

How are vaccines made

by manipulating germs or parts of germs

How do scientists decide which vaccine type will be the best

its based on the disease-causing agent and the natural behavior/course of the disease

Protective antibodies

What vaccines stimulate the recipients immune system to produce

Types of available vaccines

1. attenuated vaccines (weak, live)

2. inactivated vaccines (killed)

3. subunit vaccines (portion)

4. conjugate vaccines (polytech portion and protein)

5. toxoid vaccines (inactivated toxins)

Note on conjugate vaccines

• similar to subunit, conjugate vax uses only portions of germ

• many bacteria molecules are coated by a sugar called polysaccharide

• coating disguises germ

• immune system not to recognize it

• therefore scientists attach the polysaccharide to a stronger protein

• immune system responds to the protein, it also responses to the polysaccharide

Examples of conjugate vaccines

Haemophilus influenza conjugate vaccine (Hib) and Pneumoccocal conjugate vaccine (prevnar)

History of Polio

in early 20th century, polio was one of most feared diseases —> paralyzing thousands of children every year

• soon after introduction of effective vaccines polio was brought under control and practically eliminated as a public health problem

• Polio has been eliminated from all but four countries which remain endemic. in 2009 less than 2k cases were reported

IPV - Inactivated Polio Vaccine

developed in 1955 by Dr Jonas Salk

“Salk vaccine”

• consists of inactivated (killed) poliovirus strains of all three poliovirus types

• given by intramuscular injection and needs to be administered by a trained health worker

IPV Advantage

• as IPV is not a live vaccine, it carries no risk of vaccine associated polio paralysis

• IPV triggers and excellent protective immune response

IPV disadvantage

• IPV induces very low levels of immunity in the intestine —> when a person immunized with IPV is infected with wild poliovirus, the virus can still multiply inside the intestines and be shed in the faeces

• IPV is over five times more expensive than oral polio vaccine

• administering the vaccine requires trained health workers and sterile injection equipment and procedures

IPV Safety?

one of the safest vaccines in use

Efficacy of IPV

highly effective in preventing paralytic disease caused by all three types of poliovirus

Recommended use of IPV

most industrialized polio free countries are using IPV as the vaccine of choice. This is because the risk of paralytic polio associated with routine use of OPV is greater than the risk of imported wild virus. However as IPV does not stop transmission of the virus, oral polio vaccine is used wherever a polio outbreak needs to be contained, even in countries which rely on IPV for their routine immunization programme (polio outbreaks in the Netherlands 1992)

OPV - Oral Polio Vaccine

• developed in 1961 by Albert Sabin

• called trivalent oral polio vaccine or sabin vaccine

• simple to administer, few drops given multiple times can protect a child for life

OPV made up of?

a mixture of live, attenuated (weakened) poliovirus strains of all three poliovirus types

What does OPV produce?

Abs in the blood to all three types of poliovirus. in the event of infection, these Abs protect against paralysis by preventing the spread of wild poliovirus to the nervous system

Advantages of OPV

• administered orally (easy)

  • not need health workers/trained

• inexpensive

• safe and effective with long-lasting immunity

• can result in passive immunization of people who have not been directly vaccinated

Disadvantage of OPV

• since live attenuated —> causes paralysis

• the vaccine-associated paralytic polio (VAPP) may be triggered by immune deficiency

• very rarely the virus in the vaccine may genetically change and start to circulate among a population → also known as a circulating vaccine-derived polioviruses (cVDPV)

How is passive acquired immunity produced/transferred? How long does protection last?

antibodies produced in one person are transferred to another person to protect the latter from infection

• provides temporary protection

Two types of passive acquired immunity

natural and artificial

Natural passive acquired immunity

• Small antibodies

• IgG

• present in mothers blood cross the placenta to reach the fetus

passive acquired immunity definition

• Antibodies from an immune person are transferred to a susceptible person

Example of artificial passive acquired immunity

Hepatitis B immune globulin

Antigens

foreign organic substances that are large enough to stimulate the production of antibodies

• antigenic

• antigenic determinants

antigenic

substances capable of stimulating anitbodies

antigenic determinants

a bacterial cell has many molecules ___ on its surface that are capable of stimulating the production of antibodies

What are antibodies produced by?

• proteins produced by lymphocytes in response to the presence of an antigen

Immunoglobulins

globular glycoproteins in the blood that participate in immune reactions

The amount and type of antibodies produced by a given antigenic stimulation depend on

1. the nature of the antigen

2. the site of antigenic stimulus

3. the amount of antigen, and the number of times the person is exposed to the antigen

The majority of antigens

T-dependent Antigens because T cells are required in their processing —> the processing of T-independent antigens requires only B cells)

5 different types of antibodies

IgG

IgA

IgM

IgE

IgD

What do Plasma B cells do

produce and secrete antibodies

What does the processing of either T-dependent of T-independent antigens result in?

Results in B cells developing into plasma cells, which are capable of secreting antibodies

Primary response

the initial immune response to an antigen

• it takes 10-14 days for antibodies to be produced

Secondary response

the increased production of antibodies following the second exposure to a particular antigen

Where do immune responses occur?

immune responses to antigens in blood are usually initiated in the spleen

—> Responses to microbes and other antigens in tissues are generated in lymph nodes located near the infected area

What are antibodies

a class of glycoprotein called immunoglobulins

Antibodies and immunoglobulins saying

all antibodies are immunoglobulins but not all immunoglobulins are antibodies

hybridomas

• long-lived, antibody producing cells

• produced by combining a single plasma cell and a rapidly dividing tumor cell

monoclonal antibodies

hybridomas are capable of producing large amounts of specific antibodies

immunodiagnostic procedures

monoclonal antibodies are used in these. (i.g. immunologic procedures used in laboratories to diagnose disease)

Monoclonal antibodies are possible use in what?

fighting diseases, killing tumor cells, boosting the immune system, and preventing organ rejection

What happens when the antibody combines with an antigen

antigen-antibody complex (immune complex) is formed

Antigen antibody complexes do what

activating the complement cascade —> causing the following effects

• activation of leukocytes

• lysis of bacterial cells

• increased phagocytosis as a result of opsonization

Cell mediated immunity

• antibodies are unable to enter cells

• a complex system of cell interactions and cellular secretions

  • an arm of the immune system capable of controlling chronic infectinos by intracellular pathogens (certain bacteria, protozoa, fungi, and viruses(

Examples of cells that participate in CMI

macrophages, ThCells, TcCells, NK cells, and granylocytes

Are NK cells antigen specific or no

they are not antigen specific

NK cells

in a subpopulation of lymphocytes called large granular lymphocytes

CMI resemble what

lymphocytes but lack typical T or B cell surface markers

CMI does not increase in rate in reponse to what?

antigen and appear not to be involved in antigen-specific recognition

What do NK cells kill?

target cells, including foreign cells, host cells infected with viruses or bacteria, and tumor cells

Hypersensitivity

an overly sensitive immune system; tissue damage occurs

Different types of hypersensitivity reactions

immediate type and delayed type

immediate type (hypersensitivity)

occurs from within a few minutes to 24 hours after contact with a particular antigen; 3 types: type I, II, and III hypersensitivity reactions

delayed type

usually takes more than 24 hours to manifest themselves (poison ivy)

Anaphylactic reactions

Type I hypersensitivity reactions are also known as

Type I hypersensitivity reactions

classic allergic responses such as hay fever symptoms, asthma, gives and gastrointestinal symptoms that result from food allergies

• allergic responses to insect stings and drugs

• anaphylactic shock

• 15 - 30 min

• may be localized or systemic

localized reaction involve what kind of degranulation?

mass cell degranulation; they result in allergic reactions, such as hay fever symptoms, asthma, and food allergies

system reactions involve what kind of degranulation?

basophil degranulation; they occur throughout the body, can lead to anaphylactic shock, and can be life-threatening (drugs and insect venom)

How can anaphylactic reactions be prevented?

by avoiding known allergens (is often difficult to do)

Skin tests (scratch tests)

used to i.d. offending allergens in pateints

What does a positive scratch test indicate?

cutaneous anaphylaxis occuring at the site of the scratch

Immunotherapy

What can be used to treat an allergy patient

What is produced in response to allergy shots

IgG blocking antibodies

Type 2 hypersensitivity

antibodies directed against cell surface antigens

• cytotoxic reactions body cells are destroyed during those reactions

• few hours to take a reaction

Examples of Type 2 Hypersensitivity Reactions

blood transfusion reactions, erythroblastosis fetalis

Type III hypersensitivity reactions

immune complex reactions - such as those that occur in serum sickness and certain autoimmune diseases

• involve IgG or IgM antibodies, complement and neutrophils

Complications of untreated or inadequately treated strep throat and other streptococcus pyogenes infections

are the result of type III hypersensitivity reactions

Delayed type hypersensitivity

• type 4 hypersensitivity reactions

• cell-mediated immune reactions and are part of cell mediate immunity

• reactions are usually observed 24-48 hours or longer after exposure of contact

• DTH

DTH

prime mode of defense against intracellular bacteria and fungi

What cell types is invovled in DTH

a variety, including macrophages, cytotoxic T cells, and NK cells - antibodies DO NOT play a major role

Example of DTH

a positive TB skin test

Autoimmune Diseases

result when a person’s immune system no longer recognizes certain body tissues as self and destroys those tissues as if they were “non-self” or foreign