The Human Immune System and CD4 Counts
CD4 Part 2 of 4: Basic Human Immunology
By Richard Jannaccio on Thursday, July 31, 2014
OK, so having looked at the human anatomy associated with the immune system, let's take a look at the many types of cells that actually are involved in protecting the body, which is what the immune system is all about.
When you open the links here, you will see graphics which are meant to be viewed as you read along, so when a cell type is mentioned, look for it in the schematic diagram.
There are many different types and subtypes of specialized cells that use different processes to incapacitate disease causing microbes and other foreign substances.
We're going to take a look at the big picture and then zoom in on CD4 T Lymphocytes, the cells that we are told are killed by the so-called HIV, the cells that they claim to be counting when they arrive at "CD4 counts."
Overview:
Looking at the first graphic (overview), top right, there's a cell labeled "early lymphoid progenitor." This cell can develop into any kind of blood cell, depending on what it encounters to influence its development. It is also called a stem cell. It originates in bone marrow.
This stem cell can give rise to 2 different progenitor cells which will follow two different roads to two very different immune-function destinations.
The one labeled "Granulocyte/Macrophage Progenitor" can go on to divide and become one of many different types of cells comprising what's called the "innate immune system."
Some stem cells take the alternate route and become a "Common Lymphoid Progenitor." These can also go on to become a variety of different cells, but these cells function in what's called the "adaptive immune system."
What's the difference? As the name implies, "innate" is something that stays the way it is. "Adaptive" changes to respond to a specific challenge. The general cell types associated with both the innate and adaptive components of the immune system are shown in the second graphic.
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The cells of the "innate" immune system are always on a "seek and destroy" mission and are ready to attack whenever they encounter what they consider to be junk. If they succeed, the bacteria, virus, etc. never get to first base and are promptly killed.
The "Adaptive" immune system is the component that makes specialized "antibodies" to bind to foreign "antigens." If the innate immune cells don't get the job done, the adaptive immune system prepares itself for battle, and that can take a week or more.The adaptive immune system consists of 2 main types: B cells and T cells. B cells release free antibodies into the blood. T cells carry antibodies on their surfaces.
OK, back to the first graphic.
As you go down, from top to bottom, you see an increasing variety of different, specialized and customized cell types being produced.
The one that is labeled "Lymphoid Progenitor" will be influenced by the thymus gland to eventually become what is labeled "Double Positive." This goes on to produce 3 possible cell types NK (Natural Killer) T Cell, Cytotoxic CD8, or Helper (CD4+).
Helper (CD4+) is what the AIDS industry calls "CD4" and this is the cell that they claim is "counted" in the "CD4 Count" and, according to the dogma, is the type of immune cell that is targeted and killed by the so-called HIV.
The name CD4 comes from the CD4 glycoprotein on the surface of these cells. As we will see in the next segment, the presence of this protein is detected by labeled antibodies and that's how these cells are most often (indirectly) "counted" or estimated by lab instruments and computer software.
BUT, as you can see, this is not the end of the story. The graphic shows six subtypes of the Helper CD4+ cell. They are labeled Th1, Th2, Th3, Th17, Tfh, and iTreg. In a blood sample taken for a CD4 count, Th1 is usually most prevalent.
However, the CD4 counts do not distinguish these types. The counts combine all CD4 cells and do not tell you the percentage of each cell type. And that may be a problem, as we'll see later when we look at the research.
For now, just remember that there are six different subsets of what they are calling CD4 cells, and yet the test just gives you a single-number count. This is a little bit like being told your cholesterol level without being told the ratio of good cholesterol vs. bad cholesterol -- only much worse. The information is incomplete. Incomplete information easily leads to misinterpretation.
There's another problem. Look at the cells that resulted from following the road on the left, producing cells of the innate immune system. Three of them indicate "CD4," and although it is not labeled here, part of the ancestral line of these cells, namely Monocyte, Macrophage, and Dendritic Cell, all have CD4 on their surfaces. While some of these, such as Macrophages, can migrate from the bloodstream, Monocytes comprise 2 - 8% of total White Blood Cells (WBCs).
As we will see, there are many procedures for counting the T helper CD4+ cells, and most procedures (not all) count all cells that contain CD4 apparently without accounting for these other cells in the blood that also contain CD4. These differences in procedures can yield very different results.
We will also see that there are many opportunities for "counts" to be inaccurate. By the way, that's another misnomer. There are no "counts." There are "Estimates" that are inaccurately called "counts." As we will see, these estimates can be, so to speak, out of the ballpark.
In the next installment, we will see that the so-called "CD4 counts" can easily be very inaccurate, and whether accurate or not, the conclusions drawn, your so-called "CD4 count," can be quite invalid. Details to follow.
This lesson on the cells of the immune system was to provide basic knowledge so you can understand what the CD4 count really is claiming to "count", and what the scientific research has to say about it. That's all coming up next.
There are, of course, entire textbooks and lots of research on the human immune system, for those who are interested.
Some more advanced and detailed info (optional reading beyond what is needed for this discussion) is provided here.
Copyright 2014 by Richard Jannaccio
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