How Does T Cell Activation Occur

Today I wanted to bring up a topic that I touched on a few months back in my posts on dendritic cells, T cells, and white button mushrooms and my post on raising T cell count with Selenium. In those posts I highlighted some findings showing that mushrooms could help promote the maturation of dendritic cells. This is important because this aids in T-cell activation.

T Cell Activation

T cell activation is a complex process and it is not solely influenced by mature dendritic cells. T cell activation occurs in most cases via a two-step process. Both the T cell receptor and the CD28 molecule must be activated.

Dendritic cells, as I previously stated, work by increasing t cell count. This is overly simplified but true in basic form. What I left out in that past post, and thus far in this one, is that this is only half of the T cell activation process because the mature dendritic cells only stimulate the first half of the two-step process. For proper immune function T cell activation must occur. Both steps must complete othwise the T cell will not survive.

Step 1 - Activating The T Cell Receptor (TCR)

The first step in activating t cells is accomplished by stimulating or activating the t cell receptor by the major histocompatibility complex peptide, which is satisfied through dendritic cells that are positively influenced through a diet rich in mushrooms as previously stated in simplistic terms.

Step 2 - Activating The CD28 Molecule

The second part of the t cell activation process however is in the stimulation of the CD28 molecule with B7 proteins. --Let me reiterate here as I feel this is important. I am neither a doctor nor a scientist. I am an interested party who both loves medicine and science but who works in finance. I’m pushing my limits with this post. I feel it’s important to follow up my last post with the other half of the equation because it’s not right to mislead by highlighting only half of the t cell activation process.-- Anyway, back on topic.

What Are B7 Proteins?
B7 proteins aid in the T cell activation process by stimulating the CD28 on the T cell… but what are B7 proteins? They are peripheral membrane proteins or usually parts of various pathogens or broken down cells. Without their influence on CD28 molecules on the T cell the second half of the T cell activation process can not really occur.

Unlike the first step, we’re not really concerned with enhancing the B7 proteins like we are concerned with enhancing the maturation of dendritic cells. In this step we are more concerned with allowing the stimulation between B7 proteins and CD28 molecules to occur. This is important to recognize because the stimulation can easily be blocked and without it the T cell will not survive.

How then do we support the stimulation of B7 and CD28? This is after all the important question in tandem with how do me support maturation of dendritic cells. We ensure that the body does not block the CD28. Think of it like this. We don’t want to put a cork in the CD28. We want it wide open for B7 proteins to come into.

Blocking CD28
The cork in this case is when the T cell presents CD152 on its surface in addition to CD28. If CD152 is present the B7 proteins are drawn to it instead and the stimulation never occurs. Part two of the two step process halts and T cell activation fails. Interestingly through my research on the subject this is the area which befuddles science as this process is easily messed up. Basically science doesn’t fully understand the mechanism for CD152 and thus can’t fully manipulate it.

The way that I understand things is this. In healthy people CD152 is in balance with CD28 on the surface of the T cell. T cell activation occurs properly when the ratio of CD152 to CD28 is in balance. If immune response is warranted less CD152 is present and if immune response is not desired CD152 is more prevalent. When things aren’t working properly scientists are still working on figuring out how to manipulate CD152 for the benefit of the patient.

You Can Only Do So Much To Encourage T Cell Activation

To bring this back home and re-relate it to my previous post, there is really nothing known that you can do to encourage proper function of the second step of the T cell activation process. Yes, we can encourage the first part of the process by enhancing maturation of dendritic cells which stimulate part one of the activation but with the second part of T cell activation we are flying blind and hoping everything works out.

It’s important however, to focus on what we can do even though it doesn’t address the entire problem. As my previous post said, mushrooms aid in the maturation of dendritic cells. Assuming they are doing their job you are at least positioned to support full T cell activation when the time is right and the body and immune system is working. Do what you can and hope for the best.

Sidenote: My apologies for anybody out there that really knows the science behind all of this. I have tried my best but I’m sure this essay is not fully correct. Please if need let me know if I said anything out of line via email and I will amend this post as appropriate. This post, though it is a stretch for me to understand and explain, is very necessary to show the other side of T cell activation and how it boosts T-cells and relates to living a longer and healthier life. My previous post made it seem very easy to control when if fact it is not. Thanks for reading.

Source
Immunol Lett, 2008 January 15; 115(1): 73–74.- http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=18035425