IgM Question

[Qester]

Pretty basic question...

Can IgM be secreted into GI tract/lung/tears etc..?

I know typically to think of IgA for secretions, however I had a question regarding Selective IgA deficiency stating that they are typically asymptomatic as IgM can compensate for the absence of IgA.

Is it the J-chain that allows for secretion? If so, does IgM have a J-chain when in the blood or only when in secretions?

Thanks!

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[ilovemacaroons]

Yes. When bound via the J chain, the dimer can cross the cytoplasm and into the mucosa. Inside, the secretory component wraps around the dimer, making it undegradable by the mucosa enzymes. IgM also has a J chain so it can cross the mucosa. However, since its too bulky it doesn't cross over as much as IgA does. Source: Kaplan.

Feel free to correct me if I have mistaken.

 

[PowerDan]

Yes. When bound via the J chain, the dimer can cross the cytoplasm and into the mucosa. Inside, the secretory component wraps around the dimer, making it undegradable by the mucosa enzymes. IgM also has a J chain so it can cross the mucosa. However, since its too bulky it doesn't cross over as much as IgA does. Source: Kaplan.

Feel free to correct me if I have mistaken.

From what I understand, its not the J-chain, but the secretory piece which allows IgA to cross the mucosal barrier. The secretory piece acts as a receptor, and also protects IgA from proteolytic cleavage.

 

[Transposony]

Role of J chain in secretory immunoglobulin formation