First Aid 2012 Error on Spleen?

[rocketbooster]

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In the immunology section on pg. 223, it says splenic dysfunction = decreased IgM->decreased complement activation->decrease C3b opsonization->increased susceptibility to encapsulated bacteria.

I remember Goljan saying the splenic macrophages bind up IgG and C3b (extravascular hemolysis) while IgM in the blood causes intravascular hemolysis. Don't recall anything IgM-related to the spleen. I assumed this same mechanism accounted for why encapsulated bacteria clearance depends on the spleen. The capsule is tagged by IgG or C3b and then picked up by the splenic macrophages? I also recall in my school classes that the reason asplenic pts are susceptible to encap bacteria is because the capsule is only sensitive to IgG2 (special kind of IgG I guess) which is only made by the spleen. That was the explanation by my immunology teacher.

So, basically, I've heard different explanations on this. Which one is correct?

 

[ipizzy]

According to Kaplan qbank: splenectomized patients can have decreased IgG2 and decreased IgM because the splenic lymphocytes are the major producers of these antibodies. So everyone is right.

 

[Morsetlis]

Pentameric IgM-Ag is more potent at activating C1 esterase than IgG-Ag.

Furthermore, encapsulated bacteria with high LPS coats activate T-independent B responses which will only produce IgM.

 

[Staradmiral]

In lymphoid tissue disorders, Goljan states that splenic disfx results in decreased igM because the spleen is a major site for IgM synthesis