Antibody memory longterm

[CVIDnerd]

Hi

So, from all the research I've done, it appears that generally, when you encounter a pathogen, the relevant B-cell becomes activated (with help from helper T-cell), replicates itself into effector cells which pump out antibody for a few weeks to clear the infection, and memory cells which stick around for years in case the body encounters the pathogen again, in which case they activate again and more effector cells and antibody is released. All the information available seems to say that antibody, once loose in the blood, lasts about 3-6 weeks and only the memory B-cells stick around for a long time.

However, I was trying to understand then how it is useful to do titer tests for antibody levels (as these look at loose antibody, not B-cells). Unless you've had a recent encounter with the pathogen, surely there wouldn't be any loose antibody hanging around? I asked my immunologist and he said that in fact some of the antibody that has bound to the antigen DOES stay around in the body for years, but I can't ANY information to this effect on any scientific websites or forums.

Could anyone give me any information about this long-lasting antibody? Is it a specific type, how long does it last, what percentage of antibody normally sticks around?

Thanks!

 

[CharonY]

Mechanistically, long-term presence of antibodies are produced by a range of long-lived plasma cells from different lineages. Members of the B1 lineage are involved in the secretion of low affinity antibodies (mostly of the igM isotype, IIRC) that are maintained throughout life (also called natural antibodies) and which do not need to be induced by a specific antigen presentation. For the adaptive response the case is, to my knowledge not entirely clear. However, this knowledge is about a decade old and more information may be available now. What is assumed is that short-lived plasma blasts, (short-lived, proliferating, less differentiated)  migrated to the one marrow and terminally differentiate into plasma cells. These can be either short or long-lived. At least in mice, the long-lived plasma cells have shown to maintain adaptive serum antibody levels through the lifetime of the animal. It has been proposed that it is the balance between plasma blasts and plasma cells that ultimately decide the length for which antibody levels are maintained in blood.

 

[CVIDnerd]

Thanks! Put very basically, are you saying that it depends on the lineage of B-cell: some create antibodies that last longer than those made by other types of B-cell? Do you know where I can find any research relating to this? Excuse my asking for clarification, but I'm not a scientist, just a patient who's pretty much educating myself in immunology from scratch as I don't feel I'm getting the support or info I need from our NHS. It's fascinating stuff.

[CharonY]

For natural antibodies, I think so. But not universally for the adaptive response (the differentiation . I am not up to date on current research so I would refer you to some recent reviews. Nutt et al (Nature Reviews Immunology 15, 160–171 2015) describes the differentiation of plasma cell and their differentiation with some information on the molecular basis. However, it may be somewhat advanced. I also found an article by Chu et al. ( Scand J Immunol. 2011 Jun;73(6):508-11) which describes more how these plasma cells survive and sustain antibody production. I guess there must be some easier literature around in textbooks somewhere, but unfortunately this is not really my field and I cannot make any recommendation off to the top of my head.