Summary AQA ALEVEL BIOLOGY NOTES ON ANTIGENIC VARIABILITY

Antigenic Variation
=

refers
→
Antigenic variation to an infectious agent changing
the
proteins or
carbohydrates on its

surface ( ) thus avoids host
antigens and a immune response .




Hence when infected by the for second the
are
pathogen a time
memory cells produced
-




you ,



from first infection will different
the not
recognise the
antigens .




Influenza %
4
%
1 % 1 1 4 % 1 1 /4 #


Seasonal influenza is acute infection caused influenza
an
respiratory by viruses which circulate in
•




all parts of the world .




The influenza vaccine
changes That's because surface of influenza
-


the the the
every year .
antigens on


virus
change regularly ,
forming new strains of the virus .




of
Memory flu will other
-


cells
produced from vaccination with one strain the not
recognise strains

with different
antigens .




different
Every there different strains of the influenza virus
circulating
in the
population
-


are so a
year ,




vaccine has to be made .




New effective
vaccines
developed and chosen that is the most
against the
-



are is
one
every year
recently circulating influenza viruses .




1st infection triggers primary response 2nd infection triggers primary
-


response
-




the
(
arm >
7 a


[ 7


C.
influenza
virus
7
)
If C
influenza
virus ]
antigenic
( ) variation
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RUN
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LUV