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A 5 y/o boy with recurrent ear infections recieves booster immunization against Diphteria tetanus Petusis. His response is well below for age and sex. Peripheral B and T caunt and function are within normal range. The antibody he makes is positive for both passive hemaglutination and complement mediated lysis of tt coated erythrocytes . His antibody does not opsonize tt coated latex particles for pahagocytosis and do not directly precipitate it efficiently. The child mos likely has:
a) Affinity maturation of inmunoglobins
b) Inmunoglobin isotype switching
c) Recombination of heavy chain variable region gene
d)Recombination of light chain variable region gene
e) Somatic mutation of inmunoglobin genes
Choices C and D can be ruled out without any doubt
And so can be choice E as it says "The antibody he makes is positive for both passive hemaglutination and complement mediated lysis of tt coated erythrocytes"--> which is done by IgM .
And finally it says "His antibody does not opsonize tt coated latex particles for phagocytosis and do not directly precipitate it efficiently."
So I am thinking that the answer is a)AFFINITY MATURATION OF IMMUNOGLOBULIN
i think the answer is choice b cuz as he has a problem with opsonizatin he either has IgG or c3b defect, so if he dont have class switching so he doesnt have igG . am i right?
this child has hyper IgM syndrome and it is a problem with class switching. deficiency of CD40 L on T cells.
answer is B
RECURRENT INFECTIONS MEANS NO SECONDARY IMMU. RESPONE ,,MEANS NO SWITCHING,,
FUNCTION AND COUNT NORMAL RANGE ,,EXCLUDE A,C,D
NOT SOMATIC MUTATION ,,NO PREDISPOSING FACTES
Clearly answer should be B.therez a defect in isotype switching leading to IgG deficiency and hence opsonization defect..
answer is B
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