IgA in breast milk and passive immunity

[Sora]

A lecturer pointed out today that part of the "breast is best" idea is that IgA is transferred to the infant, which renders some passive immunity from the mother. This struck me as odd, considering that I assumed the protein would either be hydrolyzed by stomach acid or enzymatically processed. However, I did do a quick search and found that papers agree with this. Any ideas to how this might work?

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[MassTransport]

Only thing I can find is from http://home9.inet.tele.dk/birma/colose.htm, which talks about passive immunity in kittens. It claims that the antibodies survive the stomach acid and end up getting absorbed somewhere in the gut.

 

[Sora]

Only thing I can find is from http://home9.inet.tele.dk/birma/colose.htm, which talks about passive immunity in kittens. It claims that the antibodies survive the stomach acid and end up getting absorbed somewhere in the gut.

Also

http://www.springerlink.com/content/p6jk415532339120/

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=886892

 

[Mr hawkings]

A lecturer pointed out today that part of the "breast is best" idea is that IgA is transferred to the infant, which renders some passive immunity from the mother. This struck me as odd, considering that I assumed the protein would either be hydrolyzed by stomach acid or enzymatically processed. However, I did do a quick search and found that papers agree with this. Any ideas to how this might work?

There is also lysozyme and lactoferrin in the breast milk which kill gram + and gram- bacteria respectively. These also survive the digestive process.
In fact, a new movement that is afoot is trying to add recombinant versions of these protiens to infant formula to be givin to babies borne to HIV+ mothers who cannot breast-feed.
Once again, i dont know the specific mechanism by which they survive the harsh stomach conditions. They are affected though.

Fresh breast milk that has not been through the stomach acids is far superior to digested milk in terms of anti-microbial activity. SO it seems that the stomach acids and enzymes do negatively affect the IgA and other enzymes, but not completely.

 

[Sora]

SO it seems that the stomach acids and enzymes do negatively affect the IgA and other enzymes, but not completely.

Sorry to be argumentative, but there seems to be no evidence (on the explanation side) that IgA survives.

The lysozyme is on the innate side of immunity, not the passive humoral...

 

[Mr hawkings]

Sorry to be argumentative, but there seems to be no evidence (on the explanation side) that IgA survives.

The lysozyme is on the innate side of immunity, not the passive humoral...

True, but you do not secrete lysozyme in the digestive tract. Its there in the breast milk to protect the new born from bacteria in the lumen that cause gastroenteritis sice it takes several month for the baby to ramp up its own innate immune respone.

As for the IgA, I know first hand that it does survive. My lab has replicated stomach digestive environment and still been able to purify viable secretory IgA from it as part of our work. I'm sure others have done it and it is probably published somewhere. I'll look it up in the morning.

 

[Sora]

True, but you do not secrete lysozyme in the digestive tract. Its there in the breast milk to protect the new born from bacteria in the lumen that cause gastroenteritis sice it takes several month for the baby to ramp up its own innate immune respone.

As for the IgA, I know first hand that it does survive. My lab has replicated stomach digestive environment and still been able to purify viable secretory IgA from it as part of our work. I'm sure others have done it and it is probably published somewhere. I'll look it up in the morning.

Oh, sweet. That's sort of what I was looking for.

 

[Mr hawkings]

Oh, sweet. That's sort of what I was looking for.

Just so you know, i think most of the immunoglobulins do survive digestion. My boss (an ID doc) once got called in for a consult for a 6 month old who had positive titers for immunoglobulins against some funky virus (i forget specifically which one).
So naturally the medicine guys thought the baby had an infection. I learnt through my boss later that what they were detecting backgound from the mother's breastmilk against the virus.
I thought it was pretty interesting.

 

[ratbandit]

This is what they told us about colostrum in vet school, I don't know if this is the same for people so sorry if this is not helpful. Anyways, I looked it up because I knew we learned it at some point and wanted to refresh my memory!

My notes say under "absorption of colostral antibodies:"
Newborn intestines have low protease activity
Colostrum itself contains trypsin inhibitors
Newborn enterocytes have receptors that will bind colostral antibodies-(FcRn)-they bind the "constant region" of the antibody -the "Fc" portion
The antibody is then endocytosed, absorbed, and ends up in the blood stream
It also says "some IgA can be re-secreted at the mucosal surface" but I'm not really sure what/how that happens!

 

[Mr hawkings]

This is what they told us about colostrum in vet school, I don't know if this is the same for people so sorry if this is not helpful. Anyways, I looked it up because I knew we learned it at some point and wanted to refresh my memory!

My notes say under "absorption of colostral antibodies:"
Newborn intestines have low protease activity
Colostrum itself contains trypsin inhibitors
Newborn enterocytes have receptors that will bind colostral antibodies-(FcRn)-they bind the "constant region" of the antibody -the "Fc" portion
The antibody is then endocytosed, absorbed, and ends up in the blood stream
It also says "some IgA can be re-secreted at the mucosal surface" but I'm not really sure what/how that happens!

Yes the B cells right underneath the epithelial lining of the gut mucosa secrete secrtory IgA which crosses over into the lumen. This happens though later after the infant's immune system is ramped up (not a newborn).
There are also dendtritic cells which can reach their dendrites up between the cell loose junctions to sample whatever is in the lumen (including normal gut flora) and present to the other immune cells.

And i guess your explanation about the newborn digestion being different from adult digestion makes sense.

 

[turkeyjerky]

I've always heard that virtually all passive immunity is from IgG transferred in uteuro, and that the function of sIgA from breast milk is to promote normal intestinal flora.

 

[treva]

I believe it's the J chain that's added to IgA as it is secreted from mucus membranes (sec. IgA exists as a homodimer) that protects it from degredation / denaturation.

 

[alphaholic06]

I believe it's the J chain that's added to IgA as it is secreted from mucus membranes (sec. IgA exists as a homodimer) that protects it from degredation / denaturation.

I agree with this.

 

[rajb29]

I don't know if you guys figured it out, but I just saw this here and thought I could help clarify.

IgA is actually found in secretions as dimers, so you are correct to say that the J chain is present. However, the J chain's function is to just help form the dimer. When dimers are secreted, (at least through the GI tract), they bind "poly-Ig receptor", are transferred across the cell, and are secreted after the receptor is cleaved off.

HOWEVER, there is still part of the receptor left, called the SECRETORY COMPONENT (SC). This SC stays bound to the Ig, PROTECTS IT from being degraded in the intense areas of the gut, and also keeps it in the mucus by binding 'mucins'.

Hope this helps.

 

[turkeyjerky]

I don't know if you guys figured it out, but I just saw this here and thought I could help clarify.

IgA is actually found in secretions as dimers, so you are correct to say that the J chain is present. However, the J chain's function is to just help form the dimer. When dimers are secreted, (at least through the GI tract), they bind "poly-Ig receptor", are transferred across the cell, and are secreted after the receptor is cleaved off.

HOWEVER, there is still part of the receptor left, called the SECRETORY COMPONENT (SC). This SC stays bound to the Ig, PROTECTS IT from being degraded in the intense areas of the gut, and also keeps it in the mucus by binding 'mucins'.

Hope this helps.

Thanks! I'm sure I speak for everyone when I say that this issue has really been burning a hole in the back of my mind for the past 6 months.