Saturday, 7 October 2017

How long are memory B cell depleted?. Can we learn from other conditions

#Understandingyourtreatmentsspeak

We have been making the case that memory B cells are a central player in the treatment target for all drugs in MS. 

As we saw yesterday many people don't buy this idea (see below) or perhaps don't even know about this idea because they: (a) don't read the blog; (b) Don't read papers (c) cannot assimilate knowledge  or (d) all of the above:-) or (e) I'm wrong.

Yesterday I was sad, because it confirmed what I wrote above.

So I want to put more meat on the idea

I was talking about B cells and the fact there were are more than one type of cell that make up the CD19 population.

Some didn't like my slide

You (at least one of you) said I was talking "jibberish" and it is unrelated to people with MS and it was more relevant to scientists and doctors.

I said "nonsense" because, it is important in understanding the choices that you may need to make.

Is the level pitched wrongly...the answer will be yes and perhaps no...however virtually every part of the post has been explained in the past and so look at the education posts to help you get up to speed.

If you look at alemtuzumab, the CD19 B cell population (in green below) is back to normal levels within 3 months. But alemtuzumab is still working years later...so it can't be the B cell? Can it?
This is the view if you see CD19 B cells as a single population as is usually portrayed. 

So can it be the B cell?

Yes it can, because that repopulation is occurring because of immature and then mature (also called naive B cells) cell subsets come rushing out of the bone marrow to fill the space vacated by the lymphocytes that are killed. This masks the fact that memory B cells are being depleted long-term.

See our picture from Baker et al. 2017 (below). This is the pattern you see with rituximab, and HSCT so there is nothing special going on.

The blue (Total CD19+) is a composite response of the (green, pink and the baby blue). The antibody is given at 0 and 12 months and shows percentage change from baseline (-80 = 80% depletion)

This is the default pathway for B cell repopulation and will occur for all drugs that kill B cells. However, with HSCT and alemtuzumab, this occurs in the relative absence of effective T cell regulation by CD8 T cells and maybe CD4 T regs. The default pathway of T cells is the immediate repopulation comes from expansion of the memory cells, this is seen in humans and mice. There is nothing special going on. 

27 comments:

  1. Thank you MD for providing such a comprehensive and accessible post - even with my extremely limited capacity for anything scientific I have found so much of this accessible and easy to understand.
    I have been asked why Alemtuzumab works for some and not others and why the number of years of its effectiveness vary and I may now be able to explain (though if you heard it in my terms I'm sure I'd make you wince!)
    As I'm due my three days of Alemtuzumab in a couple of weeks time I'm gonna be saying my Hail Marys that them there memory B cells stay well and truly done for!
    Best wishes for your efforts to have this perspective accepted and endorsed by others in your scientific community.
    Have a good weekend.

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  2. Great post, thank you for all the effort that clearly went into this ��

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  3. If Alemtuzumab does not get rid of brain lesions
    won't someone always have a chance of disease resumption.

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    Replies
    1. If we look at the NEDA rates recently presented about 60% or more people had some activity.

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  4. Great post, MD.
    I am missing something important: Do you need to mount a new response to infection in order to repopulate memory Bcells?

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    1. I think this may be part of the slow repopulation but as drug is gone nothing to stop repopulation occuring. After alemtuzumab you can be vaccinated. After HSCT you have to be vaccinated as you have a new repertoire. I think that if the planes cells Sur I've you existing immunity survives so maybe not much of a driving force for new b cells.

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  5. Ok I'm sold. Makes sense, data fits, sounds logically. However. Unless I'm being dumb, why does Alemtuzumab produce superior brain atrophy then b depleting agents? Granted alemtuzumab works on two front. One makes immune less tolerant of the original infection. 2nd depleting memory cells. Surely inspite of the first effect b cell still drives the progression as the disease as your paper explains. But inspite this Ocrelizumab should have superior brain atrophy data?

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    1. Ok. We are comparing apples and pears. Because we Don't have real world data for ocrelizumab since its just been approved in March 2017 so the need to look at clinical trial data. However, the real world data for alemtuzumab is still good in terms of brain atropy. Where as the neda for ocrelizumab is almost excellent. Reducing inflammation by 98%. Inspite the difference in patient selection between the two, it seems ocrelizumab brain atrophy should be in the highs given it's efficacy in total suppression on inflammation? Where as neda for alemtuzumab is okay.

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    2. Good point becuase they should be the same. However are we comparing like for like?

      In the alemtuzumab trials people i think people were on treatment within two years but looking at the cladribine it takes four years to be on drug and for ocrelizumab it was about 3.8 years so is the difference due 2 extra years of loss of brain reserve.

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  6. For sure noone argues that B cells play a leading role in autoimmune diseases, but the arguement is if they are the soldiers or the generals. One unanswered question that cannot be ignored is that where the selection of organs comes from, if it is just the memory B cells. One could imagine many reasons apart from that it stems from the different types of T cells involved, but the secondary autoimmunity that emerges from Lemtrada deletes many of them I think...
    The predisposition for Lemtrada's s.autoimmunity is only a theory also.
    The involvement of CD4-CD8 is weak since DMF depletes those for long term after treatment yet the disease is not improved. So, DMF is probably all about the Bcells. Still that doesn't dispove of the idea of T cell involvement.
    I see in one of the papers that you have posted here that another subtype of T cells is depleted together with RTX, which is the CD3 in MS and it is different than the one in RAs RTX. Does this have something to say to us?
    Also, the non responders are patients that created antibodies or there are other reasons involved? A different anti20 drug can answer that.

    Also, how long does a memory b cell live? Even if the drugs cannot reach the brain, since these agents affect both the blood and the lymph glands, wouldn't eventually, after some reasonable time, the B cells accumulated in the brain die and not be replaced?

    Thank you very much for your article, really appreciated!

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    1. Where is the selection for the organs very good question. I don't know I can give the lame answer and say it is a specific antibody to something in the CNS,which is about as good as it gets for the T cell.

      CD3 is a T cell it is expressed by cd4 and CD8.

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    2. How long do memory cells live is another great question and also we need to ask how long do plasma cell live
      B cells in culture tend to die very quickly or within a couple of weeks
      I don't know enough about b cells to answer these and profG and I was talking about this on Friday.

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    3. Anon 6.58
      I think CD3 is all T cells? ie no subset?
      Re memory B, I've got a horrible feeling that the ones with ebv in might live forever? Even worse, my brain is stuffed full of 'em :(

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    4. "b cells are the cockroachs of the immune system"

      one study found
      IgG1+ memory B cells specific for the 1918 pandemic
      strain of influenza virus circulating in the blood of survivors
      90 years after primary exposure to the virus.

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    5. "How long do memory cells live"

      Longevity. To determine which types of cells and which
      types of molecules are required for memory B cell survival,
      previous studies have used IgG+ memory B cells
      as a target. IgG+ memory B cells can persist in the
      absence of T cells or input from precursor cells, but
      experiments using mice with follicular dendritic cells
      (FDCs) in which the gene encoding complement receptor
      2 (Cr2) has been knocked out have suggested that
      there is a requirement for FDCs for the maintenance
      of IgG+ memory B cells44. In these mice, the primary
      IgG response was unaffected, but the secondary antibody
      response was significantly decreased. Notably,
      the impaired memory response corresponded with the
      reduced frequency of antigen-specific memory B cells.
      Thus, one straightforward interpretation is that CR2 on
      FDCs promotes the survival of IgG+ memory B cells,
      directly or indirectly, possibly by functioning as a depot
      for antigen–antibody–complement complexes; however,
      the role of antigen persistence in memory responses
      is debated (see below).
      Inducible deletion of phospholipase Cγ2 (PLCγ2)
      after the generation of IgG1+ memory B cells substantially
      decreased the size of the memory B cell
      compartment, which suggests a requirement for
      BCR signalling for IgG1+ memory B cell survival45.

      Memory B cells doi:10.1038/nri3802

      Obrigado

      Luis

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    6. PLC-γ2 is essential for formation and maintenance of memory B cells

      Abstract

      Resting antigen-experienced memory B cells are thought to be responsible for the more rapid and robust antibody responses after antigen reencounter, which are the hallmark of memory humoral responses. The molecular basis for the development and survival of memory B cells remains largely unknown. We report that phospholipase C (PLC) γ2 is required for efficient formation of germinal center (GC) and memory B cells. Moreover, memory B cell homeostasis is severely hampered by inducible loss of PLC-γ2. Accordingly, mice with a conditional deletion of PLC-γ2 in post-GC B cells had an almost complete abrogation of the secondary antibody response. Collectively, our data suggest that PLC-γ2 conveys a survival signal to GC and memory B cells and that this signal is required for a productive secondary immune response.
      https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699133/

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    7. Thanks for this. I'll have a look. The CR2 = EBV receptor...ProfG asked how long does antigen persist on the follicular dendritic cell (a cell that keeps B cells going).

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    8. This was released earlier this year but I can't have access to it.
      First Atlas of B-cell Clones in Human Body Forms New Foundation for Infectious Disease Research

      https://www.pennmedicine.org/news/news-releases/2017/august/first-atlas-of-b-cell-clones-in-human-body-forms-new-foundation-for-infectious-disease-research

      "Our fantasy for the future is to create organ-specific immune monitoring assays. If we can define features of the antibody repertoire that are unique to particular tissues, we may be able to monitor tissue-specific immune responses using blood-based clinical lab tests.”

      Such tests might be used to monitor immune responses to vaccines or inappropriate antibody responses in organ-specific autoimmune diseases; however, the first step towards that is knowing the location of B-cell clones.

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  7. Well, this is some post MD! Like Fi this morning, I'm stunned by how much I've understood so well done indeed, top marks for accessibility :)
    Thank heavens for SLE and RA research, profiling B cells for the last 10 years. 'Clinical response to rituximab is associated with depletion of CD19+CD27+ memory B cells' lost track of which excellent paper I've copied that from ;-)
    So who are the responders? How on earth can we know if we don't profile B cells whilst on dmt?
    That's the best line ever 'treat infrequently and monitor' get it printed on a T-shirt and wear it to ECTRIMS.

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    1. The MS Society has just supported us to be able to look at this very aspect

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  8. Excellent post Md

    One of the best i have ever seen (wonder how manny hours it took to complete)

    As a true scientific assay it raises more questions than provides
    answers

    According to this review tfh and also Dendritic folicular cells are needed for a robust B cell memory response

    "In summary, there are multiple pathways for generating
    B cell memory. Although T cell-independent memory
    B cells can be generated as discussed above, it seems
    that their recall response is quantitative, rather than
    qualitative, in nature. Thus, aside from the increased frequency
    of antigen-specific B cells, it is unclear whether
    T cell-independent memory B cells have an intrinsic
    advantage compared with their naive B cell counterparts
    to respond more rapidly and more robustly to antigen,
    as is seen in T cell-dependent B cell memory. Therefore,
    we hereafter focus on several aspects of canonical,
    T cell‑dependent memory B cells."

    IgG+ memory B cells can persist in the
    absence of T cells or input from precursor cells, but
    experiments using mice with follicular dendritic cells

    (FDCs) in which the gene encoding complement receptor
    2 (Cr2) has been knocked out have suggested that
    there is a requirement for FDCs for the maintenance
    of IgG+ memory B cells44. In these mice, the primary
    IgG response was unaffected, but the secondary antibody
    response was significantly decreased. Notably,
    the impaired memory response corresponded with the
    reduced frequency of antigen-specific memory B cells.
    Thus, one straightforward interpretation is that CR2 on
    FDCs promotes the survival of IgG+ memory B cells,
    directly or indirectly, possibly by functioning as a depot
    for antigen–antibody–complement complexes; however,
    the role of antigen persistence in memory responses
    is debated (see below).

    Although virusspecific
    memory B cells can be activated in the absence
    of T cells57, T cell help is a strict requirement for the
    reactivation of memory B cells that are specific for monomeric
    protein antigens

    Memory B cells doi:10.1038/nri3802

    Anyway I dont think its only t cells or memory B (even follicular dendritic)
    Maybe they are all working togheter


    Anyway i see your post have some aditions to your previous woork

    Ps: Good luck with your Ectrims adventure hope you get thru those

    skeptical looking neuros

    Glad to be helping

    Obrigado

    Luis


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  9. After all those dreadfull long lived plasma b cells can be knock down (hopefully)

    Just found this

    Proteasome Inhibition with Bortezomib
    Depletes Plasma Cells and Autoantibodies in
    Experimental autoimmune myasthenia gravis.

    https://www.ncbi.nlm.nih.gov/pubmed/21239719

    Long-lived plasma cells are early and constantly
    generated in New Zealand Black/New Zealand
    White F1 mice and their therapeutic depletion
    requires a combined targeting of autoreactive

    https://www.ncbi.nlm.nih.gov/pubmed/25889236

    Obrigado
    plasma cells and their precursors

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  10. It is great to have a plasma depleter but I don't know if this is the big challenge that MS has to deal with (I am not underestimating it).
    My concern is that MS is one problem that becomes two problems: the infammation that turns on neurodegeneration.
    Can the mechanism of neurodegeneration stop automatically when inflammation stops?
    The best measure we have for neurodegeneration is brain atrophy and only HSCT and Lemtrada have possitive results on stoping it (but we are not sure what happens there-especially with HSCT). We are waiting for Cladribine results but I am guessing it will be reducing the atrophy but not stoping it (Tysabri is supposed to reduce brain atrophy, we need to know how too).
    We don't have to wait for Ocrevus results (I dont think its potent form is enough). Thankfully neurologists have been using Rituxan for 10 years now and it didn't prevent the progressive form to come, so we kinda know.
    I am afraid that the fact that O. does not penetrate the brain is deal breaker for us and neurodegeneration and IF it can just stop after the stop of inflammation is our real challenge.
    (Yes, I can say these now that we have the B-cells drugs...)

    PS Louis you shoot faster than your shadow ;)

    Thanks

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    1. Neuroprotection
      LA demonstrated a 68% reduction in annualized PCBV and suggested a clinical benefit in SPMS while maintaining favorable safety, tolerability, and compliance over 2 years.
      Classification of evidence: This study provides Class I evidence that for patients with SPMS, LA reduces the rate of brain atrophy.

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    2. Yes, I have read the theory about mitochondrial dysfunction (and I take LA myself) but it seems (to me) like an effect of neurodegeneration, not a cause. 68% is impressive if you compare it with MS drugs, but still the water tube is broken and you take the water out with a bucket...

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  11. HI. Ironically I have MS but am searching for information on secondary immunodeficiency. A family member at about ago 9 had rituxan treatment for a rare kidney disease (FSGS). He's now 13 & the docs think he may have developed secondary ID due to this. From you post I see why he would have been fine for a while & is now getting sick. A question from his mom is, what are the odds he could ever make his own B cells again. I would think he would have to have a successful bone marrow transplant. I'm no doctor but know enough so search like crazy on the web. Your thoughts &/or guidance to other resources are appreciated.
    Thanks, Shelley

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