Immunity in children

[Karl Roberts]

Hello all,
	One of our anatomy instructors asked me to post this question 
concerning immune activity in children.  Let's see what you have to say:

	A child appears to be healthy until about 9 months of age. Then 
he develops severe bacterial infections, one after another.  Fortunately, 
the infections are successfully treated with antibiotics.  When infected 
with the measles and other childhood diseases, the child recovers without 
unusual difficulty.  Explain the different immune system response to 
these infections.  Why did it take so long for this disorder to become 
apparent (hint- IgG)?

Thanks in advance for your responses.
Joe