SCIT 1408 Applied Human Anatomy and Physiology II - Immune System Chapter 21 A

8/18/2019 SCIT 1408 Applied Human Anatomy and Physiology II - Immune System Chapter 21 A

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

The Immune System: Innate and Adaptive Defenses

Figure 21.1

Non-

specific

Specific

1st line

2nd line

Phagocytosis,

cells, chemicals

Inflammation

3rd line

B, T cells


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First Line of Defense: Surface Barriers

Skin, mucous membranes, and their secretions

Skin- Keratin:

Presents a physical barrier to most microorganisms

Is resistant to eak acids and bases, bacterialen!ymes, and to"ins

#ucosae pro$ide similar mechanical barriers


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First Line of Defense: hemica! Barriers

%pithelial membranes Skin acidity &p' of ( to )* inhibits bacterial groth

Sebum- chemicals to"ic to bacteria

Stomach mucosae-'+l, protein-digesting en!ymes

Sali$a lacrimal fluid contain lyso!yme, Ig

.igesti$e respiratory systems- #ucus ciliatrap e/ect bacteria


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Second Line of Defense: e!!s and hemica!s

Phagocytes

Natural killer &NK* cells

ntimicrobial proteins in blood and tissue fluid

Inflammatory response &macrophages, mast cells, 0B+s,and chemicals*

Surface carbohydrates on pathogens ser$e as

antigens


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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21.2a

Second Line of Defense: "hagocytes

#acrophages, monocytes &in blood*, neutrophils

&blood tissues*, mast cells, eosinophils

1ree: ander thru tissue in search of cellular debris

1i"ed: Kupffer cells &li$er*

#icroglia &brain*


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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21.2#

$#%

Lysosome

&icro#e adheres to phagocyte.

"hagocyte forms pseudopods that

eventua!!y engu!f the partic!e.

"hagocytic vesic!e is

fused 'ith a !ysosome.

&icro#e in fused vesic!e

is (i!!ed and digested #y

!ysosoma! en)ymes 'ithin

the phago!ysosome* !eaving

a residua! #ody.

Indigesti#!e andresidua! materia!

is removed #y

e+ocytosis.

"hagocytic vesic!e

containing antigen

$phagosome%.

,esidua! #ody

Acid

hydro!ase

en)ymes

"hago!ysosome

-

2

1

/

Phagocytosis


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Second Line of Defense: 0atura! i!!er $0% e!!s

Nonspecific

2arge granular lymphocytes

Bind targets &recogni!e as 3non-self4*

Induce apoptosis of targets

2yse cancer cells, $irus-infected cells

5elease perforins, other cytolytic chemicals %nhance inflammation



Second Line of Defense:Inf!ammation

Non-specific response to in/ury

Pre$ents the spread of damaging agents to nearby tissues

.isposes of cell debris and pathogens

Sets the stage for repair processes

'allmarks:

1. Red (rubor)

2. Hot (calor)

3. Swollen (tumor)

. Painful (dolor)



To!!!i(e ,eceptors $TL,s%

#acrophages and cells lining the gastrointestinal

and respiratory tracts bear T25s

T25s recogni!e specific classes of infecting

microbes

cti$ated T25s trigger the release of cytokines

that promote inflammation



Inf!ammatory ,esponse: "hagocytic

&o#i!i)ation

1our main phases: 2eukocytosis 6 neutrophils are released from the

bone marro in response to leukocytosis-inducingfactors released by in/ured cells

#argination 6 neutrophils cling to the alls ofcapillaries in the in/ured area

.iapedesis 6 neutrophils s7uee!e through capillary

alls and begin phagocytosis

+hemota"is 6 inflammatory chemicals attractneutrophils to the in/ury site


11/45Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21.-

0eutrophi!s enter #!ood

from #one marro'

3ndothe!ium

Basement mem#raneapi!!ary 'a!!

&argination

Diapedesis

"ositive

chemota+is

Inf!ammatory

chemica!s diffusing

from the inf!amed

site act as chemotactic

agents

1

2

-

Inf!ammatory ,esponse: "hagocytic &o#i!i)ation


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Second !ine of "efense# Inflammation


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4omeostatic Im#a!ance

Inflammation does not clear infection debris

bscess &Pus not cleared*

58: I .

9ranulomas 6 infectious granulomas such as tuberclescontaining Mycobacterium tuberculosis

5esistant to digestion by #acrophages

Infected macrophages ith fibrous capsule +an remain asymptomatic until immunocompromised


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Second Line of Defense:Antimicro#ia! "roteins

ttack microorganisms ;r inhibit reproduction

Interferon

+omplement proteins


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Interferon $IF0%

I1N synthesi!ed by $irus infected cells I1N diffuses to nearby cells, stimulate synthesis of proteins

&PK5* that inhibit $iral replication

PK5 is nonspecific inhibits replication of all $iruses #any types of I1N from many different cell types

lpha I1N used:

s an anti$iral drug against hepatitis + $irus

To treat genital arts caused by the herpes $irus


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Interferon $IF0%

Figure 21./


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omp!ement

proteins in blood in an inacti$e form

Proteins include +? through +@, factors B, ., and

P, and regulatory proteins Pro$ides a ma/or mechanism for destroying foreign

substances in the body


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Second Line of Defense: Antimicro#ia! "roteins

omp!ement

cascade of r"ns that amplifies inflammation,nonspecific specific immune responses

Kills bacteria, cells &punches holes in membranes*

+lassical Pathay acti$ates specific immunity by:

b binds pathogen

+? binds to g-b comple" lternate Pathay by: factors B, ., P surface

polysaccharides of microorganisms


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omp!ement "ath'ays

Figure 21.6


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Second Line of Defense: Antimicro#ia! "roteins5

reactive "rotein $,"%

Produced by li$er in response to: Infection

Inflammation

Csed as clinical marker to assess the abo$e

Binds to pathogens targets them for:

Phagocytosis

;psoni!ation

+omplement acti$ation


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Second Line of Defense: Fever

body temperature

In response to infection by microorganisms or

e"posure to antigens

#oderate fe$er ;K: 2i$er, spleen se7uester iron !inc from pathogens

metabolic rate speeds up tissue repair

Too high, denatures en!ymes


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Adaptive Defenses $Specific Immune ,esponse%

dapti$e immune system- functional system :

5ecogni!es antigens &anything foreign*

ntigen-specific, systemic, and has memory

cts to immobili!e, neutrali!e, or destroyforeign substances

mplifies inflammatory response andacti$ates complement

'umoral 6 antibody-mediated immunity

+ellular- cell-mediated immunity


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Specific Immune ,esponse : Antigens

Anything the body perceives as foreign; “non-self”

utoimmune diseases

Substances that stimulate an immune response

Pathogenicity or $irulence is defined as the degree

to hich a pathogen can %D.% the immuneresponse


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Specific Immune ,esponse : omp!ete Antigens

1unctional properties:

Immunogenicity 6 ability to stimulate proliferation

of specific lymphocytes and antibody production

5eacti$ity 6 ability to react ith acti$ated

lymphocytes and the antibodies released in

response to them

+omplete antigens- foreign protein, nucleic acid,

some lipids, and large polysaccharides

Csually large molecules


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Specific Immune ,esponse: 4aptens $Incomp!ete

Antigens%

Small moleculesE peptides, nucleotides, manyhormonesE

not immunogenic

are reacti$e hen attached to protein carriers

'apten > bodyAs protein F immune response as inallergies

'aptens in poison i$y, dander, some detergents,and cosmetics


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Specific Immune ,esponse : Antigenic Determinants

Immunogenic part of ag

ntibodies and acti$ated lymphocytes bind to

antigenic determinants

#ost antigens Fnumerous antigenic determinants : #obili!e se$eral different lymphocyte populations

1orm different kinds of antibodies against it

2arge, chemically simple molecules &eGgG, plastics*

ha$e little or no immunogenicity


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Specific Immune ,esponse : Antigenic Determinants

Figure 21.7


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Specific Immune ,esponse: &4 "roteins

#a/or 'istocompatibility +omple"- self antigens,

uni7ue to an indi$idual

+lass I #'+ 6 on all body cells

+lass II #'+ 6 on certain cells in$ol$ed in theimmune response

These are the markers that ill elicit graft re/ection transfusion r"ns


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Specific Immune ,esponse: e!!s of Adaptive Immune

System

?G B lymphocytes or B cells 6 humoral immunityE

ab production


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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21.8

S$ecific Immune Res$onse# !ym$hocyte %aturation,ed #one

marro'

Bone marro'Thymus

Lymph nodes*

sp!een* and other

!ymphoid tissues

Immature

!ymphocytesircu!ation

in #!ood

Immunocompetent*

#ut sti!! naive*

!ymphocyte migrates

via #!ood

Activated

Immunocompetent

B and T ce!!s

recircu!ate in

#!ood and !ymph

9 Site of !ymphocyte originey:

9 Site of antigen cha!!enge*

activation* and fina!diff erentiation of B andT ce!!s

9 Site of deve!opment of immunocompetence as

B or T ce!!s5 primary!ymphoid organs

Lymphocytes destined

to #ecome T ce!!s

migrate to the thymus

and deve!op

immunocompetence

there. B ce!!s deve!op

immunocompetence

in red #one marro'.

After !eaving the thymus

or #one marro' as nave

immunocompetent ce!!s*

!ymphocytes ;seed< the

!ymph nodes* sp!een* and

other !ymphoid tissues

'here the antigencha!!enge occurs.

Antigenactivated

immunocompetent

!ymphocytes circu!ate

continuous!y in the

#!oodstream and !ymph

and throughout the

!ymphoid organs of

the #ody.

11

1

22

2


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T e!! Se!ection in the Thymus Immunocompetence

Figure 21.=

&olerance'

recogniesbinds* %H+

Immunocom$etence' hasonly mild r,n to %H+

after binding- 2


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B e!!s Immunocompetence

B cells become immunocompetent and self-tolerant

in bone marro

Some self-reacti$e B cells are inacti$ated &anergy*

hile others are killed

;ther B cells undergo receptor editing in hich

there is a rearrangement of their receptors


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Immunocompetent B or T ce!!s .isplay uni7ue receptors 6 responds to 3that4 antigen

Become immunocompetent before encounteringantigens they attack

re e"ported to secondary lymphoid tissue here

encounters ith antigens occur

#ature into fully functional antigen-acti$ated cells

upon binding ith their recogni!ed antigen

It is genes, not antigens, that determine hich

foreign substances our immune system ill

recogni!e and resist


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Antigen"resenting e!!s $A"s%

?G Phagocytose antigens 6 partially digest


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Adaptive Immunity: Summary

'umoral, +ellular

B T lymphocytes, P+s, and specific molecules

to identify and destroy nonself particles

Its response depends upon the ability of its cells to: 5ecogni!e foreign substances &antigens* by

binding to them

+ommunicate ith one another so that the holesystem mounts a response specific to those

antigens


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4umora! Immunity ,esponse

ntigen challenge 6 first encounter beteen an

antigen and a nai$e immunocompetent cell

In spleen or other lymphoid organ

B cell receptor binds ag, receptor-mediatedendocytosis of the cross-linked antigen-receptorcomple"es, T cell acti$ationinteraction

B cell forms clones of identical cells &clonal

selection* Specific b produced against specific ag

"rimary ,esponse Antigen

A ti #i di


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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21.1>

"!asma

ce!!s

Secretedanti#ody

mo!ecu!es

!one of ce!!s

identica! to

ancestra! ce!!s

Su#se?uent

cha!!enge #y

same antigen

&emory

B ce!!

&emory

B ce!!s

"!asma

ce!!s

Secreted

anti#ody

mo!ecu!es

Secondary ,esponse

$can #e years !ater%

$initia! encounter

'ith antigen%

Antigen #inding

to a receptor on a

specific B !ymphocyte

$B !ymphocytes 'ith

noncomp!ementary

receptors remain

inactive%

"ro!iferation to

form a c!oneB !ympho#!asts


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Fate of the !ones

Secreted antibodies:

Bind to free antigens

#ark the antigens for destruction by specific or

nonspecific mechanisms

+lones that do not become plasma cells become

memory cells that can mount an immediate

response to subse7uent e"posures of the same

antigen


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Immuno!ogica! &emory

Primary immune response 6 cellular differentiation

and proliferation, hich occurs on the firste"posure to a specific antigen

2ag period: ( to H days after antigen challenge

Peak le$els of plasma antibody are achie$ed in ?=

days

ntibody le$els then decline


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Immuno!ogica! &emory

Secondary immune response 6 re-e"posure to the

same antigenE amnestic response

Sensiti!ed memory cells respond ithin hours

ntibody le$els peak in < to ( days at much higher

le$els than in the primary response

ntibodies bind ith greater affinity, and their

le$els in the blood can remain high for eeks to

months


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"rimary and Secondary 4umora! ,esponses

Figure 21.11

Ig# Ig9


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Active 4umora! Immunity

B cells encounter antigens and produce antibodies

against them

Naturally ac7uired 6 response to a bacterial or $iral

infection

rtificially ac7uired 6 response to a $accine of

dead or attenuated pathogens

Daccines 6 spare us the symptoms of disease, and

their eakened antigens pro$ide antigenic

determinants that are immunogenic and reacti$e


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"assive 4umora! Immunity

.iffers from acti$e immunity in the antibody

source and the degree of protection B cells are not challenged by antigens

Immunological memory does not occur

Protection ends hen antigens naturally degrade inthe body

Naturally ac7uired 6 from the mother to her fetus

$ia the placenta

rtificially ac7uired 6 from the in/ection of serum,such as gamma globulin


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Types of Ac?uired Immunity

SCIT 1408 Applied Human Anatomy and Physiology II - Immune System Chapter 21 A

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Transcript of SCIT 1408 Applied Human Anatomy and Physiology II - Immune System Chapter 21 A