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Lymphocytes and Your Lab Tests: Why Are They Important?

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Published on September 25, 2014

T cells, B cells, natural killer cellsall funny names, but how are they are significant when understanding your lab test results?

Find out from University of Massachusetts Dartmouth laboratory scientist Dr. Susan Leclair as she takes us on a step-by-step exploration of lymphocyte function and their role in your immune function and response.

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Transcript | Lymphocytes and Your Lab Tests: Why Are They Important?

Please remember the opinions expressed on Patient Power are not necessarily the views of our sponsors, contributors, partners or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That’s how you’ll get care that’s most appropriate for you.

Dr. Leclair:

This is Professor Susan Leclair from U Mass Dartmouth, and we're going to start a series here on a rather confusing or perhaps difficult to explain set of cells called lymphocytes, so you're just going to have to bear with this.  We'll probably go through maybe two or three segments just on normals, I think, because part of the problem with lymphocytes is we didn't know what they did until the late 1960s.

Originally, the only thing lymphocytes were for was that the small one was about the same size as a red cell, and those of us who were using microscopes without a sizing instrument called micrometer could use them to judge whether or not red cells were big or small.  Because no one knew what they did, Robert Good at the University of Minnesota, for those of you who are out in the Midwest, discovered and explained the immune system.  So really in one sense we're talking about a cell that's still being explained, still being explored. We don't exactly know all of the details.

The first classification that Robert Good came up with was something called a B and a T cell, and he called them B and T cells because in the chicken, which was his experimental model, there were a lot of cells clustered in a particular organ of the chicken called the bursa, so that was B.  And the other population of cells were clustered in another area of the chicken called the thymus. Humans have a thymus. We don't have a bursa.

So why do we keep the word B?  Because fortunately for us and for my failing memory it turns out that the B bursa cells from the chicken are found in humans in the bone marrow.  So you can think about them as B for bone marrow, T for thymus, which is a gland, and it's found, by the way, right about here, the thymus.  The bone marrow is wherever you want to poke a hole, but the thymus is right here, right between the breastbone and your heart, so it's kind of noticeable when physicians are checking around things like that.

So who cares?  T cells are bossy.  They are born supervisors.  Yes, they will do work occasionally, but more often than not they like to boss other cells.  So what happens is an antigen, a staph from a staph infection or strep from strep throat or something like that comes into your body.  Monocytes go and they eat that particular organism.  They then degrade it into little pieces.  They pick out a piece that is antigenic, that is something that a lymphocyte will respond to, and in a very complex dance that we really don't understand completely that mono will go to the lymphs in the thymus or wherever they can find them because they circulate, and hand over to this T cell this antigen as if to say,  “Okay, I broke it down for you, and it's ready for you. Now go do something.”

That T lymphocytes then has to make a decision, “Do I kill this thing myself?  Do I recruit somebody else to kill it for me?  And do I have to remember this?”  If it kills it itself, it literally sidles up to anything that's got that antigen, so thinking of your throat right now and a strep throat, a lot of lymphocytes are coming into that area.  That's why it gets swollen. That's why it gets red.  All of that inflammation is happening in there, and those T cells will literally come side to side to that bacteria and will pour into that bacteria—very intimate relationship here—deadly chemicals and cause that bacteria to die.

If it doesn't want to do that, if it's, you know, in its office doing paperwork, then it's going to recruit other cells, and one of those other cells is called an NK cell, a natural killer cell. It's not going to use natural killer cells against staph typically.  It might use it against TB or a fungus or a different kind of antigen.  And what it will do is it will go over to the NK cells and stimulate them, give them marching orders and say, “Go kill that thing,” and will sit there causing more and more NK cells to become recruited to do this work.

When the T cell is in an active recruitment mode, when it knows that's what it's going to do, it changes things on its membrane to allow itself to be able to do that. And those changes in the membrane can be identified, they can be tested for, and a recruiting T cell can be called a T-4 cell because of the markers that are on the outside of that cell.

So you've got this whole bunch of T cells, and you've got this smaller bunch over here that are recruiting NK cells or recruiting some other cell to participate in this immune response.  Those are T-4 cells.  We sometimes call them the cell that's going to turn on your immune system.

Maybe in another situation, immunizations against the flu would be a good one.  You go and you have a shot for the flu.  Well, that's nice.  Now what happens?  The monocyte gets ahold of what was in that serum, breaks it down to the important component parts, brings it over to the T cell and says, “I don't know what you're going to do with it, but fix it.  Do something.”

The T cell then looks at it and says, “Okay, I need to defend against this but not immediately.  I need to be able to make an antibody that will stay around long enough so that six months, a year from now, whenever I will have sufficient antibodies there to be able to defend against this particular antigen.”  That's what B cells do. B cells are from the bone marrow.  They make antibodies, so there's a lot of B’s in there. B cells are going to make those antibodies for you.

So in the case of your immunization, the first day, outside of your arm hurting a little bit, not much is going on because there's a lot of processing going on. And then for the next three weeks or so you're going to get B cells busily making antibodies against the flu vaccine.  So, yeah, you're going to feel a little sluggish, and a lot of people will say, “Oh, I got the flu shot, and I got the flu.”  No, but you are getting an immune response.

So when somebody wrote in recently and said, “If I got my flu vaccine two weeks ago, what's that going to do to my blood count?” The answer is probably not raise it too much right now because it was a vaccine, but you are going to have more lymphocytes that are going to be seen as active, that are making antibodies that are responding to this immunization.  It happens to everybody when you get some kind of—whether it's the flu vaccine, or it's whooping cough vaccine or any of those, that goes on with everybody, and it's a normal response to the kind of immunization that you're looking for.

These particular B cells are also being programmed by that same T-4 cell to make memory.  So if you had whooping cough or you had the immunization against whooping cough, you have a population of B lymphocytes floating around in your system that are happily doing nothing.  Well, not exactly.  They're surveying, they're checking out the neighborhood, but they only have to work if you ever come in contact with whooping cough. So if you go visiting your grandchildren some day, and we all know that they are collections of infections ready to be given to almost anybody, and you pick up your lovely grandchild who promptly proceeds to, you know, get nasal goo all over you, lovely—it's only grandparents who thinks that's cute—then you'll have your B cells ready to protect yourself against whatever it is that your grandson or daughter just gave to you.

So those are memory cells.  They kind of float around, wandering, doing their own thing, because they're only interested in maybe one or two kind of antigens that they’re working on.  But eventually this immune response should stop.  I made enough cells, I got rid of the tuberculosis, I got rid of the strep throat, although I am going to remember strep throat because I don't want to have it again, so I need to shut off my immune system.  And you shut your immune system off by a sub—subpopulation of T cells known as T-8 cells.

So T-4s turn on, T-8s turn off.  You want to have a healthy balance of those two.  Too many T-4s, everything is on, and your immune system is on overdrive.  Too many T-8s, your system is permanently turned off, and you don't have an immune system.  So you need to keep these in a balance, and every now and then in certain diseases they will ask for a test that measures the T-4 and the T-8 load, and they will measure the ratio between the two so they have a sense of how are your lymphocytes really functioning on this immunologic level.

Oh, I think that's more than enough for now, so we'll continue this the next time.  If you have any questions, and again, I'm pretty sure you will, don't forget, write to questions@patientpower.info

And remember that knowledge is sometimes your best medicine.

Please remember the opinions expressed on Patient Power are not necessarily the views of our sponsors, contributors, partners or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That’s how you’ll get care that’s most appropriate for you.

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