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  #1  
Old 06-05-2011
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Blocked nbme 7 mannose binding lectin

This post has been deleted because it's not allowed to post NBME Questions, for more information read here
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  #2  
Old 06-06-2011
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Mannan binding lectin def
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Old 06-06-2011
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You're right to think its MAC complex, but remember that C56789 will make up the MAC, so its best to say MBL Pathway.

The deficiency is infact C5-C9 (MAC) Complex, so answer is E.
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Old 06-06-2011
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D. C8

From FA: "Deficiency of C5-C8 leads to Neisseria bacteremia."

The MAC attack complex can be formed from other ways, not just by the MBL pathway, so even if that was deficient the MAC would be formed. This patient has all the symptoms of bactermia due to Neiserria (gram neg diplococci) so her deficiency is somewhere in C5 through C8, and the only option that fits that choice is C8, answer D.
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Old 06-06-2011
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Yes it should be D.

MAC deficiency is classically associated with increased susceptibility to Neisseria infections.

List of other complement deficiencies...



Regarding MBL pathway. Just remember that the complement system can be activated through three pathways: the classical pathway, the alternative pathway, and the mannose-binding (MB) lectin pathway




Source*
http://www.bio.davidson.edu/courses/.../Mohr/MBL.html
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Old 06-06-2011
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Kaplan videos 2010
Immunology Chapter 7 d Complement (video)
min 15min 15seg

MAC deficiency (C5-C8) => Neisseria
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Old 06-06-2011
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This is odd, because I read this:

Quote:
N. meningitidis is capable of eliciting an innate immune response via several mechanisms, and this innate response is particularly critical for efficient immune clearance. First, the mannose binding lectin (MBL) pathway is instrumental in activating compliment mediated phagocytosis of the bacteria. Next, the recognition of capsular lipooligosaccharide (LOS) triggers the TLR4 pathway, which initiates a signal transduction process that attracts phagocytes, activates macrophages and dendritic cells, and ultimately leads to the phagocytosis and destruction of the offending bacteria6. LOS and other lipopolysaccharide structures can also trigger the alternative pathway
http://www.brown.edu/Courses/Bio_160...neresponse.htm
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Old 06-06-2011
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"The importance of complement in innate immunity against meningococcal infection is emphasized by the marked susceptibility of people with complement deficiencies to systemic disease (Box 1). While people with reduced levels of C3 or C4 are at increased risk [13], the most striking association is among individuals who lack components of the MAC; this association has been described in numerous family studies [17,18]. Affected individuals have an increased lifetime risk of meningococcal disease of 100010 000-fold compared with the general population, and can present with multiple attacks [19]."

Trends in Microbiology
Volume 15, Issue 5, May 2007, Pages 233-240
Interactions between Neisseria meningitidis and the complement system
full text: Neisseria meningitidis and the complement system.pdf
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