Host Defenses II: Specific Immunity and Immunization

Chapter(13.6((

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Specific(Immunity(and(Vaccina8on((• Natural(immunity:**any*immunity*that*is**acquired*through*the*normal*biological**experiences*of*an*individual*

• Ar8ficial(immunity:((protecAon*from*infecAon**obtained*through*medical*procedures*such*as**vaccines*and*immune*serum*

Specific(Immunity(and(Vaccina8on((• Ac8ve(immunity(((-  occurs*when*an*individual*receives**

immune*sAmulus*that*acAvates*B*and*T**cells*to*produce*immune*substances**such*as*anAbodies*

-  creates*memory*that*renders*the*person**ready*for*quick*acAon*upon*re3exposure**to*the*same*anAgen*

-  requires*several*days*to*develop*

-  lasts*for*a*relaAvely*long*Ame*

Specific(Immunity(and(Vaccina8on((• Passive(immunity(

-  occurs*when*an*individual*receives**anAbodies*from*another*source*

-  recipient*is*protected*for*a*short*period*of**Ame**

-  transfer*of*anAbodies*from*mother*to*child*in#utero##or*through*breasGeeding*

-  transfusion*of*gamma*globulin*

-  anA3snake*venom*

The(Four(Types(of(Acquired(Immunity(Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Natural Immunity is acquired through the normal life experiences of a human and is not induced through medical means.

Active After recovering from infectious disease, a person will generally be actively resistant to reinfection for a period that varies according to the disease. In the case of childhood viral infections such as measles, mumps, and rubella, this natural active stimulus provides nearly lifelong immunity. Other diseases result in a less extended immunity of a few months to years (such as pneumococcal pneumonia and shigellosis), and reinfection is possible. Even a subclinical infection can stimulate natural active immunity. This probably accounts for the fact that some people are immune to an infectious agent without ever having been noticeably infected with or vaccinated for it.

Passive Natural, passively acquired immunity occurs only as a result of the prenatal and postnatal mother-child relationship. During fetal life, IgG antibodies circulating in the maternal bloodstream are small enough to pass or be actively transported across the placenta. This natural mechanism provides an infant with a mixture of many maternal antibodies that can protect it for the first few critical months outside the womb, while its own immune system is gradually developing active immunity. Depending on the microbe, passive protection lasts anywhere from a few months to a year.

Another source of natural passive immunity comes to the baby by way of the mother�s milk. Although the human infant acquires 99% of natural passive immunity in utero and only about 1% through nursing, the milk-borne antibodies provide a special type of intestinal protection that is not available from transplacental antibodies.

Artificial Immunity is that produced purposefully through medical procedures.

Active Vaccination exposes a person to a specially prepared microbial (antigenic) stimulus, which then triggers the immune system to produce antibodies and lymphocytes to protect the person upon future exposure to that microbe. As with natural active immunity, the degree and length of protection vary.

Passive Passive immunotherapy involves a preparation that contains specific antibodies against a particular infectious agent. Pooled human serum from donor blood (gamma globulin) and immune serum globulins containing high quantities of antibodies are frequently used.

Table 13.10 The Four Types of Acquired Immunity

(girl): © Floresco Productions/Corbis RF; (mother): © Ingram Publishing/Superstock (RF); (boy): © The McGraw-Hill companies, Inc./Jill Braaten, photographer; (patient): © Brooke Fasani Auchincloss/Corbis (RF) Copyright © 2009 Pearson Education, Inc.

The*acquired*immune*response*counters*specific*invaders*

•  Our*immune*system**–  Responds*to*foreign*molecules*called*an8gens*

•  The*acquired(immune(system((–  Reacts*to*anAgens*–  And*�remembers�*an*invader*

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Lymphocytes*mount*a*dual*defense*

•  Two*kinds*of*lymphocytes*carry*out*the*immune*response*

–  B(cells*–  Secrete*anAbodies*

–  T(cells(–  AOack*cells*infected*with*bacteria*or*viruses*

–  Millions*of*kinds*of*B*cells*and*T*cells*–  Each*with*different*membrane*receptors*

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AnAgens*have*specific*regions*where*anAbodies*bind*to*them*

•  An8gens(–  Most*are*proteins*or*polysaccharides*on*the*surfaces*of*

–  Viruses*–  Foreign*cells*

•  An8genic(determinants(–  Specific*regions*on*an*anAgen*–  To*which*anAbodies*bind*

Antigen molecule

Antibody B molecule

Antibody A molecule

Antigen- binding sites

Antigenic determinants

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Clonal*selecAon*musters*defensive*forces*against*specific*anAgens*

•  When*an*anAgen*enters*the*body*–  It*acAvates*only*a*small*subset*of*lymphocytes**–  Those*with*complementary*receptors*

•  The*selected*lymphocyte*cells*mulAply*into*clones*(copies)*of*short3lived*effector*cells*

–  Specialized*for*defending*against*the*anAgen*that*triggered*the*response*

–  And*into*memory*cells*that*confer*long3term*immunity*

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Clonal*selecAon*musters*defensive*forces*against*specific*anAgens*

•  The*steps*of*clonal(selec8on*–  Primary(immune(response,*clonal*selecAon**

–  Produces*effector(cells*–  Memory(cells*that*may*confer*lifelong*immunity*

–  Secondary(immune(response*–  Memory*cells*are*acAvated*by*a*second*exposure*to*

the*same*anAgen*–  This*iniAates*a*faster*and*stronger*response*

Antibody molecules

Primary immune response

B cells with different antigen receptors

Cell activation: growth, division, and differentiation

Antigen receptor (antibody on cell surface)

First exposure to antigen

Endoplasmic reticulum

Effector cells secreting antibodies Memory cells Antigen molecules

Second exposure to same antigen

Endoplasmic reticulum

Antibody molecules

Effector cells secreting antibodies Memory cells

Secondary immune response (May occur long after primary immune response.)

5 4

3

2 1

6

Antigen molecules

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Clonal*selecAon*musters*defensive*forces*against*specific*anAgens*

•  Primary*vs.*secondary*immune*response*–  The*primary*immune*response*

–  Occurs*upon*first*exposure*to*an*anAgen*–  Is*slower*than*the*secondary*immune*response*

–  The*secondary*immune*response*–  Occurs*upon*second*exposure*to*an*anAgen*–  Is*faster*and*stronger*than*the*primary*immune*

response*

Time (days)

Second exposure to antigen X,

first exposure to antigen Y

First exposure to antigen X

Secondary immune response to

antigen X

Primary immune response to

antigen Y

Primary immune response to

antigen X

Antibodies to X

Antibodies to Y

Ant

ibod

y co

ncen

trat

ion

56 49 42 35 28 21 14 7 0

Immuniza8on:((A(Lively(History(*• First*recorded*aOempt*at*immunizaAon*occurred**in*6th*century*China*-  consisted*of*drying*and*grinding*up*smallpox*

*scabs*and*blowing*them*with*a*straw*into**the*nostrils*of*vulnerable*family*members*

• Variola8on*in*the*10th*century*-  deliberate*inoculaAon*of*dried*pus*from*

*smallpox*pustules*of*one*paAent*into*scratches**on*the*arm*of*a*healthy*person*

-  used*in*parts*of*the*Far*East*unAl*Lady**Montagu*brought*it*to*England*in*1721*

-  unfortunately,*many*recipients*and**their*contacts*sAll*died*of*smallpox*

Immuniza8on:((A(Lively(History(*• Edward(Jenner:**1796*-  inspired*by*a*dairymaid*who*had*been**

infected*by*cowpox*and*who*was**immune*to*smallpox*

-  tested*his*theory*by*injecAng*a*young**boy*with*material*from*human*cowpox**lesions,*exposed*him*to*smallpox*2*months**later,*and*was*immune*to*the*disease*

*-  vaccina8on:**any*immunity*obtained*by*

*inoculaAon*with*selected*anAgens(

Ar8ficial(Ac8ve(Immunity:((Vaccina8on(*• Basic*principles*behind*vaccinaAon*-  sAmulate*a*primary*response*and*a**

memory*response*

-  prime*the*immune*system*for*future**exposure*to*a*virulent*pathogen*

-  if*the*pathogen*enters*the*body,*the***response*will*be*immediate,*powerful,**and*sustained*

• Vaccines*have*profoundly*reduced*the**prevalence*and*impact*of*many*infecAous**diseases*that*were*once*common*and*deadly*

Principles(of(Vaccine(Prepara8on(*• QualiAes*of*an*effecAve*vaccine*-  protect*against*exposure*to*natural,**

wild*forms*of*the*pathogen*

-  have*a*low*level*of*adverse*side*effects**or*toxicity*

-  sAmulate*both*anAbody*(B3cell)*and**cell3mediated*(T3cell)*response*

-  long3term,*lasAng*effects*(produce*memory)*

-  not*require*numerous*doses*or*boosters*

-  inexpensive,*have*a*relaAvely*long*shelf**life,*and*be*easy*to*administer*

Principles(of(Vaccine(Prepara8on(*• Whole*cell*or*virus*vaccines*

-  live,*aOenuated*cells*or*viruses*

-  killed*cells*or*inacAvated*viruses*

• AnAgenic*molecules*derived*from*bacterial*cells**or*viruses*(subunits)*

-  subunits*derived*from*cultures*of*cells**or*viruses*

-  subunits*synthesized*to*mimic*natural***molecules,*oaen*via*geneAc*engineering*

*-  conjugated(vaccines:**subunits*aOached*to

*proteins*to*make*them*more*immunogenic(

Development(of(New(Vaccines(*• Dozens*of*bacterial,*viral,*protozoan,*and*fungal*diseases*remain*without*a*funcAonal*vaccine*-  malaria,*HIV/AIDS,*diarrheal*diseases,*

*respiratory*diseases,*and*worm*infecAons**that*affect*over*200*million*people*per*year*

• Difficult*to*design*vaccines*for*latent*or***persistent*viral*infecAons*-  herpesviruses*and*cytomegaloviruses*

Route(of(Administra8on(and((Side(Effects(of(Vaccines(*• Most*vaccines*are*administered*via*the*routes*below*

-  subcutaneous*

-  intramuscular*

-  intradermal*

-  nasal*and*oral*vaccines*- available*for*only*a*few*diseases*

Vaccine(Administra8on(*• Adjuvant:**special*binding*substance*required**by*some*vaccines*-  enhances*immunogenicity**-  precipitates*the*anAgen*and*holds*it*in**

the*Assues*so*that*it*will*be*released**gradually*

*-  most*common*adjuvant:**alum*(aluminum*

*hydroxide*salts)*

Vaccine(Side(Effects(*• Vaccines*must*go*through*years*of*trials*in*experimental*animals*and*human*volunteers**before*they*are*licensed*for*general*use*

• SAll*some*complicaAons*occur*-  local*reacAons*at*the*injecAon*site*

-  fever*

-  allergies*

-  some*rare*adverse*reacAons*

Vaccine(Side(Effects(*• Recent*studies*have*aOempted*to*link**vaccines*to*later*development*of*diabetes,**asthma,*and*auAsm*-  the*study*linking*the*MMR*vaccine*to**

auAsm**has*been*discredited*and*the**principal*author�s*medical*license*was**revoked*

-  independent*studies*have*shown,**unequivocally,*that*the*MMR*vaccine**does*not*cause*auAsm**

Vaccine(Side(Effects(*• Price*of*not*vaccinaAng*

-  outbreaks*of*measles,*mumps,*diphtheria,**polio,*typhoid*fever,*and*whooping*cough**

-  decrease*in*the*level*of*herd(immunity,*a**phenomenon*in*which*a*certain*percentage**of*the*populaAon*is*vaccinated,*making*it**impossible*for*the*microbe*to*circulate**

• Geeng*vaccinated*serves*the*common*good,*as**well*as*the*individual*good*

• Many*young*parents*have*no*memory*of*the**pre3vaccinaAon*era*and*don�t*appreciate*the**greater*risk*of*not*vaccinaAng*their*children**

Vaccine(Side(Effects(*• In*the*decade*before*the*measles*vaccine*was**available*-  3*–*4*million*cases*of*measles*per*year*

-  300*–*400*children*died*annually*

-  1000*more*chronically*disabled*due*to**measles*encephaliAs*

• Childhood*vaccines*save*the*lives*of*2.5*million**children*a*year*worldwide*(UNICEF)*

• Risks*from*infecAous*disease*almost*always**outweigh*the*chance*of*an*adverse*vaccine**reacAon*

To(Vaccinate:((Who(and(When?(*• CauAon*must*be*exercised*in*giving*live**vaccines*to*immunocompromised*or*pregnant**paAents*

• VaccinaAon*recommended*for*all*typical*childhood*diseases*for*which*a*vaccine*is*available*

• VaccinaAon*in*adults*to*�boost�*older*immunizaAons,*protect*against*adult*infecAons,*and*to*provide*special*protecAon*in*people*with*certain*medical*condiAons*

Concept(Check((

Determine*which*of*the*statements*below*describes*ac8ve*or*passive*immunity:**

A.  infusion*of*gamma*globulin*B.  recovery*from*influenza*C.  receipt*of*the*influenza*vaccinaAon*D.  anAbodies*passed*from*mother*to*infant*through*

breasGeeding*