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Before birth, in the bone marrow millions of different B-cells are formed. These cells are differentiated and express different antibodies.

Are these the only B-cell types you will ever have? Or can the body generate new types of B cells, with new antibodies to deal with newly encountered threats?

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Are these the only B-cell types you will ever have? Or can the body generate new types of B cells, with new antibodies to deal with newly encountered threats?

New B cells are constantly formed throughout one's life; the B cells that are present in the newborn are constantly supplemented by newly formed B cells.

... there is no statistical difference in the rate of production of new immature B cells in the marrow of young and old animals. In total, our results confirm previous work showing that mature B cells in old mice have a slower turnover, but more importantly suggest that the defect in mature B cell turnover is not due to a decline in B lymphopoiesis, but rather an inability of the newly made cells to replenish the peripheral compartments.

--Aging and developmental transitions in the B cell lineage.

But the second part of your question seems to have a misconception. The newly-formed B cells have no relationship to newly-encountered threats. No matter what new pathogens you encounter, your newly-formed B cells don't reflect them; they are formed randomly, and it is only by chance that any particular B cell might be able to react with a new threat. Fortunately, there are so many B cells that the chance of at least a few reacting is very high, even though only a tiny fraction of the whole B cell population can do so.

Although new threats (mainly) require new B cells, repeated threats don't -- once a B cell is stimulated the first time, it undergoes a pathway that functionally makes it longer lived and more effective, so that on repeat exposure these optimized B cells are called in and there's much less need for the new naive B cells.

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After the body is alerted to the presence of antigens, it calls in the artillery, which in this case are the white blood cells (phagocytes). The phagocytes digest as many of the antigens as they can, and then report back to the lymphocytes (B cells). The digested antigen material inside the phagocyte is then given to the lymphocyte, so it can produce an antibody to neutralize the antigen. This is similar to using snake venom to make anti-venom.

If the antigen attacks again in the future, the lymphocytes 'remember' the antigen and release the antibody, which they already know how to make, saving time and getting rid of the antigen before the human is even aware of its presence or it's excretion from the body. This is the basic concept behind vaccines and immunity. So to answer your question, yes, we can and do form new antibodies regularly. If we didn't, every new virus strain would be fatal.

Edit: As requested this is a source I found that is way more detailed and science-y - https://www.ncbi.nlm.nih.gov/books/NBK26884/

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  • $\begingroup$ This answer is misleading. You are describing what happens with mature B cells following antigen exposure, which is a completely separate thing from whether newly-formed B cells continue to arise throughout an individual's life. $\endgroup$ – iayork Jan 19 '17 at 17:08
  • $\begingroup$ @iayork Damn you're actually right. Probably should have read the question better but this is all I remember so I thought I've give my two cents. $\endgroup$ – user45808 Jan 19 '17 at 17:11
  • $\begingroup$ @user45808 that's fine, but unfortunately your two cents are irrelevant and somewhat misleading. Not all white blood cells are phagocytes, not by a long shot. Similarly, not all lymphocytes are B cells. Digested antigens are not "given to" the lymphocyte like a delivery person handing off a package - they are presented on the antigen-presenting cell's surface for cognate receptors to bind to, recognize, and stimulate the resting B (or T) cell. Also, not all cell-mediated immunity to repeat exposures to antigen happen without the host's knowledge - some infections still take time to fight off. $\endgroup$ – MattDMo Jan 21 '17 at 4:13

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