definition of immunity
immunity: resistance to a specific disease
definition of antigen
antigen: “substance” that induces the immune response, e.g., bacteria, viruses
definition of antibody
antibody:“products” of immune response; globulin type of protein
Immunoglobulin
immunoglobulin: – an antibody, immune globulin, Ig
IgM:
first antibody produced in immune response
indicates current or recent infection or exposure to antigen
IgG:
second antibody produced in the immune response
indicates past infection (when IgM absent)
Antigenic stimulation of B cells (lymphocytes) yields:
clone of antibody–producing cells (plasma cells)
clone of memory cells (ready to jump into action if the same antigen comes along again)
Immune response after primary immunization
no detectable antibodies for a week or longer
a small burst of IgM antibodies occurs first
a small burst of IgG antibodies follows
Immune response after second, third, and booster shots:
almost immediate response due to activation of memory cells
a small burst of IgM
a large burst of IgG provides protective levels of antibody
Clinical case VS Sub-Clinical Case
A person may have a CLINICAL case of a disease (have symptoms) or may have a SUB –CLINCIAL case (no symptoms). In both instances the person will make IgM antibodies first and then IgG specific antibodies that can be detected by a blood test – will tell if a recent or past exposure.
What is TITER?
The amount of antibody present is expressed as its TITER (i.e. how much antibody is present). For example, you may have had a Rubella titer performed. If the results indicate that you have no immunity (you never had the disease or an effective immunization), or that the titer is too low to be protective, you will be requested to have an immunization.
Factors Affecting Response to Immunization
- Differences in immune response by host
-inheritance
-diseases affecting immune system
-general health - Site of injection
-type of tissue
-fat may absorb antigen so it does not reach B cells - Immunization product
-manufacturers striving to improve vaccines and toxoids to give better immune response and fewer adverse reactions - Product Failure
-bad batch from manufacturer
-improper storage may inactivate
Products Used for Immunization
- Vaccine: suspension of bacteria or virus, altered so not able to cause disease but still antigenic … causes production of antibodies
e.g., pertussis vaccine, measles vaccine - Toxoid: bacterial exotoxin treated so no longer toxigenic (harmful) but still antigenic … causes production of antibodies
e.g., diphtheria toxoid, tetanus toxoid
Types of Immunity
- Artificially acquired:
-product given for the purpose of providing immunity … usually means a needle - Naturally acquired:
-an act of nature such as having a disease or antibodies transferred from mom to baby - Passive immunity:
-host given preformed antibodies
-protection available immediately
-used for disease treatment and occasionally short term prevention - Active immunity:
-host makes own antibodies when given or exposed to antigen
-antibodies not available for days or weeks (takes longer if -this is first exposure to antigen)
-used for disease prevention … long term
Routine Immunization Schedule
Nothing until 2 months old
-diptheria, pertussis, tetanus (DPT)
-polio
-Haemophilus influenzae type B (Hib) – can cause meningitis
-MMR – , measles (rubeola/red measles), mumps, rubella (german measles)
-Chicken pox (Varicella)
-Meningococcal conjugate (for some types of Neisseria meningitis)
-Pneumococcal conjugate (for some types of Streptococcus pneumoniae)
-hepatitis B
-yearly influenzae
-Booster shots: diphtheria and tetanus every ten years
Rubella Immunization
- Symptoms of rubella (German measles):
mild infection, rash (head, face, neck, trunk) for 2 – 3 days
many cases subclinical (no symptoms) - Danger during pregnancy:
virus can cross placenta to infect fetus
fetus may be aborted or stillborn
if baby carried to term, may be several defects (deafness, cataracts, mental retardation, heart defects) - Immunization:
vaccine containing rubella virus (MMR = measles, mumps, rubella)
part of childhood series; preferably before puberty
do not immunize if pregnant or expecting to become pregnant within 3 months
immunize males and females to eliminate viral reservoir
law in some provinces that all health care workers have immunity to rubella; need proof of vaccination or presence of rubella antibodies (blood test)
Immunization against Hepatitis B
- Who should be immunized:
all health care workers at risk of exposure to blood or fluids capable of transmitting infection, or who are at risk of sharps injuries - Schedule:
three shots of hepatitis vaccine
first two are one month apart, third is six months after first - Protective level of antibodies: after 3rd shot
- Successful immunization: blood test for antibodies … anti HBs
- Booster: under review … may be required after 5 years if antibodies lacking
- Hepatitis Immune Globulin (HBIG):
-passive immunization product with preformed antibodies
-given after a blood or mucous membrane exposure to hepatitis B virus when there is no evidence of anti–HBs in the health care worker
-provides short term protection for that incident …. must be given within 48 hours
Immune Status to Chicken Pox
- Chicken pox virus (varicella–zoster) causes:
-chicken pox: a generalized infection characterized by fever, malaise and vesicular eruptions; spread by respiratory secretions or contact with vesicular fluid; 2– 3 weeks incubation period; more severe in adults than in children
-shingles: reactivation of the latent virus in older and immuno compromised patients; causes painful eruptions in peripheral nerve endings, often around waist; a person cannot get shingles without previously having had chicken pox (they may not know or remember that had chicken pox at one time) - Chicken pox can be a serious threat to immunodeficient patients
- Measures to reduce risk to patients:
-determine immune status of health care workers in advance
-Immunization of non–immune health care workers
-Non– immune health care worker exposed to chicken pox should not be around immuno compromised patients from day 10–21 following exposure (chicken pox incubation period 14 –21 days…. because could be shedding virus from 10 th day post exposure and not know it until symptoms appear)
Why tuberculosis is currently a serious problem
-increase in the number of people infected and diseased
-emergence of drug–resistant strains
How is tuberculosis spread
-direct contact with respiratory secretions
-droplet nuclei: greatest danger because they remain suspended in the air, the bacteria remain viable for a long time, and the particles are too small to be trapped by cilia lining the respiratory tract
Usual sequence of events following inhalation of tubercle bacilli:
-bacteria multiply slowly in the lung for 3 – 6 weeks
-cellular immune system becomes activated during this time
-spread of bacteria halted – walled off by a group cells – called a granulonmata
person is infected but does not get disease and is not contagious
Incidence of Tuberculosis
-only about 5% of those infected develop TB
-another 5–10% of those infected may develop disease later in life when the immune system breaks down; dormant bacteria are reactivated
Symptoms of Tuberculosis
initially vague … persistent cough; fever of unknown origin
later … bloody sputum, organ dysfunction as other organs infected
Tuberculin skin test:
-intradermal injection in forearm of solution containing tubercle protein
-read in 48 hours for raised, hard area
-this is not a vaccine
Reasons for positive tuberculin skin test:
Your body has seen tubercular protein “sometime, somehow, somewhere”
-person currently has tuberculosis
-person had tuberculosis in past
-person inhaled bacteria; infected but no disease (5% may develop disease later in life)
-person has been immunized against tuberculosis (BCG vaccine)
When tuberculin testing is done:
at start of employment in health care
on a regular basis following the initial testing
following a known exposure
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IPC - Module 143
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IPC - Module 290
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IPC - Module 351
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IPC - Module 449
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Summary - IPC Module 112
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Summary - IPC Module 224
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Summary - IPC Module 324
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Summary - IPC Module 418
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Module 1 Test21
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Module 2 Test37
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Module 3 Test35
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Module 4 Test29
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Summary - IPC Module 547
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Module 5 Test32
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Module 6 Summary40
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Module 6 Test59
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Module 7 Test27
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Module 7 Summary23
