IMMUNOASSAY
TYPES OF IMMUNIZATION
Two main types of immunization exist. In passive immunization, antibodies
(protective proteins) are injected into the body and provide immediate, but short-
lived, protection against specific disease-causing bacteria, viruses, or toxins.
Active immunization primes the body to make its own antibodies against such
microorganisms and confers longer-lasting immunity.
PASSIVE IMMUNIZATION
1
Blood is taken
from a person
or, rarely, an animal
previously exposed
to a particular
microorganism.
The blood will
contain antibodies
against that
microorganism.
2
An extract from
the blood
containing the
antibodies (known
as immune serum
or antiserum) is
injected into the
person to be
protected.
3
The antibodies
help to destroy
the microorganism
if it is present in the
blood or enters it
over the following
few weeks.
Disease-causing
microorganism
ACTIVE IMMUNIZATION
I
The person to
be protected is
inoculated with a
killed or modified
microorganism
(vaccine) that does
not cause disease.
2
The immune
system is
provoked to make
antibodies against
the modified
microorganism;
it also retains
a “memory” ofthe
organism.
Antibody
__________
Ifthe real
3
microorganism
then enters the
blood, antibodies
...
....
cb—■
^ H
y
>
y
can be produced
quickly and in
large numbers.
xxx
Disease-causing
microorganism
t y p e s
o f T - l y m p h o c y t e :
h e l p e r
c e l l s ,
w h i c h p l a y a r o l e i n t h e r e c o g n i t i o n o f
a n t i g e n s ,
a n d
k i l l e r
c e l l s
( t h e
s e c o n d
t y p e o f T - l y m p h o c y t e ) , w h i c h a r e a c t i -
v a t e d b y h e l p e r c e l l s a n d d e s t r o y c e l l s
t h a t h a v e b e e n i n v a d e d .
im m u n e s y ste m d is o rd e rs
D i s o r d e r s
o f t h e
i m
m
u n e
s y s t e m
i n -
c l u d e i m
m
u n o d e f i c i e n c y d i s o r d e r s a n d
a l l e r g y
,
i n w
h i c h t h e i m
m
u n e s y s t e m
h a s a n i n a p p r o p r i a t e r e s p o n s e t o u s u -
a l l y i n n o c u o u s a n t i g e n s s u c h a s p o l l e n .
I n
c e r t a i n
c i r c u m s t a n c e s ,
s u c h
a s
f o l l o w i n g
t i s s u e
t r a n s p l a n t s ,
i m m u n o -
s u p p r e s s a n t d r u g s
a r e u s e d t o s u p p r e s s
t h e i m
m
u n e s y s t e m
a n d t h u s p r e v e n t
t h e b o d y r e j e c t i n g t h e d o n o r t i s s u e a s
a f o r e i g n o r g a n i s m .
im m u n ity
A
s t a t e
o f
p r o t e c t i o n
a g a i n s t
d i s e a s e
t h r o u g h t h e a c t i v i t i e s o f t h e
i m m u n e
sys-
tem
.
N a t u r a l
( i n n a t e )
i m m u n i t y
i s
p r e s e n t
f r o m
b i r t h
a n d
i s
p a s s i v e l y
a c q u i r e d f r o m t h e m o t h e r t h r o u g h t h e
p l a c e n t a . A c q u i r e d ( a d a p t i v e ) i m m u n i t y
d e v e l o p s
e i t h e r
t h r o u g h
e x p o s u r e
t o
i n v a d i n g
m i c r o o r g a n i s m s
o r
t h r o u g h
i m m u n i z a t i o n
a n d c a n b e a c t i v e o r p a s -
s i v e . A c t i v e
i m m u n i t y
o c c u r s
t h r o u g h
v a c c i n a t i o n
w i t h
k i l l e d
o r
w e a k e n e d
m i c r o o r g a n i s m s ,
w h i c h
p r i m e s
t h e
b o d y t o p r o d u c e a n t i b o d i e s a s a d e f e n c e
a g a i n s t f u t u r e i n v a d e r s o f t h i s t y p e ; p a s -
s i v e
i m m u n i t y
i n v o l v e s
t h e
a d m i n -
i s t r a t i o n o f s p e c i f i c a n t i b o d i e s t o f i g h t
t h e
i n f e c t i o n ,
f o r
e x a m p l e ,
f o l l o w i n g
e x p o s u r e t o c h i c k e n p o x .
im m u n iz a tio n
T h e
p r o c e s s
o f
a r t i f i c i a l l y
i n d u c i n g
i m m u n i t y
a s a p r e v e n t i v e m e a s u r e a g a i n s t
i n f e c t i o u s d i s e a s e s
.
TYPES AND BENEFITS
I m m u n i z a t i o n m a y b e a c t i v e o r p a s s i v e .
I n t h e p a s s i v e f o r m
,
a n t i b o d i e s
a r e i n -
j e c t e d
i n t o
t h e
b l o o d
t o
p r o v i d e
i m m e d i a t e
b u t
s h o r t - l i v e d
p r o t e c t i o n
a g a i n s t s p e c i f i c
b a c t e r i a
,
v i r u s e s
,
o r
t o x -
i n s
.
A c t i v e
i m m u n i z a t i o n ,
a l s o
c a l l e d
v a c c i n a t i o n , p r i m e s t h e b o d y t o m a k e
i t s o w n a n t i b o d i e s a n d c o n f e r s l o n g e r -
l a s t i n g
i m m u n i t y .
I t
a l s o
p r o t e c t s
t h e
m
o r e v u l n e r a b l e m e m b e r s o f a c o m
m
u -
n i t y , s u c h a s t h e v e r y o l d o r t h e v e r y
y o u n g ( s e e
h e r d i m m u n i t y
).
WHO SHOULD BE IMMUNIZED
R o u t i n e c h i l d h o o d i m m u n i z a t i o n p r o -
g r a m m e s
e x i s t
f o r
d i s e a s e s
s u c h
a s
d i p h t h e r i a
,
t e t a n u s
,
p e r t u s s i s
,
p o l i o m y e l -
i t i s
,
a n d h a e m o p h i l u s i n f l u e n z a e
( H i b )
( s e e
D T a P / I P V / H i b
) ; m e a s l e s , m u m p s , a n d
r u b e l l a ( s e e
M M R v a c c i n a t i o n
);
m e n i n g i t i s
C ; a n d t u b e r c u l o s i s ( s e e
B C G v a c c i n a t i o n
).
F o r i n j e c t i o n s a n d t i m i n g s ,
s e e
T y p i c a l
c h i l d h o o d i m m u n i z a t i o n s c h e d u l e
,
o v e r l e a f .
A d d i t i o n a l
i m m u n i z a t i o n s
m a y
a l s o
b e n e c e s s a r y b e f o r e f o r e i g n t r a v e l ( s e e
t r a v e l i m m u n i z a t i o n
) .
POSSIBLE RISKS
I m m u n i z a t i o n s
a r e
u s u a l l y
g i v e n
b y
i n j e c t i o n ,
a n d m o s t
o f t h e m
h a v e
n o
a f t e r - e f f e c t s .
S o m e
v a c c i n e s ,
h o w e v e r ,
c a u s e p a i n a n d s w e l l i n g a t t h e s i t e o f
i n j e c t i o n
a n d
m a y
p r o d u c e
a
s l i g h t
f e v e r o r f l u l i k e s y m p t o m s . O t h e r s m a y
p r o d u c e
a
m
i l d
f o r m
o f t h e
d i s e a s e .
V e r y r a r e l y , s e v e r e r e a c t i o n s o c c u r a s a
r e s u l t o f , f o r e x a m p l e , a n a l l e r g y t o o n e
o f t h e
v a c c i n e ’s
c o m p o n e n t s .
N o t
a l l
i m
m u n i z a t i o n p r o v i d e s
c o m p l e t e p r o -
t e c t i o n
a g a i n s t
d i s e a s e ;
t y p h o i d f e v e r
v a c c i n a t i o n s ,
i n
p a r t i c u l a r ,
g i v e
o n l y
p a r t i a l p r o t e c t i o n .
P e o p l e w i t h
i m m u n o d e f i c i e n c y d i s o r d e r s
o r w h o h a v e w i d e s p r e a d
c a n c e r
,
o r t h o s e
t a k i n g o r a l
c o r t i c o s t e r o i d d r u g s
s h o u l d n o t
r e c e i v e v a c c i n e s
c o n t a i n i n g
l i v e
o r g a n -
i s m s . T h o s e w h o h a v e p r e v i o u s l y h a d a
s e v e r e r e a c t i o n t o a v a c c i n e s h o u l d n o t b e
i m m u n i z e d . S o m e v a c c i n e s s h o u l d n o t b e
g i v e n t o
y o u n g
c h i l d r e n ,
d u r i n g
p r e g -
n a n c y , o r t o H I V p o s i t i v e i n d i v i d u a l s .
im m u n o a s s a y
A
g r o u p
o f
l a b o r a t o r y
t e c h n i q u e s ,
w
h i c h i n c l u d e r a d i o i m m u n o a s s a y a n d
E L I S A ( e n z y m
e - l i n k e d i m
m
u n o s o r b e n t
a s s a y ) , t h a t a r e u s e d i n t h e d i a g n o s i s o f
i n f e c t i o u s d i s e a s e s , t o c o n f i r m
i m m u n -
i t y
,
a n d a l s o t o i n v e s t i g a t e
a l l e r g i e s
.
T h e
I
413
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