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“Though
this is not a nutritional question per se, we thought it deserved an answer.”
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T-Cells
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Question:
I understand that there are 4 types of T-cells: killer, helper, suppresser,
and... what is the fourth one and what does it do? (January, 2000)
Ken Stringer, Administrator
and Webmaster of Jennifer Jensen's
Nutrition Power web site responds: Though this is not a nutritional
question per se, we thought it deserved an answer. So we sought the input
of what I'll call a "Visiting Professor to the Virtual Faculty". We thank
George Carter for his response. George is the Director of Treatment Information
Development at Direct AIDS Access Information Resources (DAAIR) as well
as a treatment advocate for ACT UP New York. George has written extensively
on treatment options, including nutritional and herbal ones, and they are
available on the DAAIR Web Site. From
the home page select "HIV Treatment Info Pages" and then "Articles" for
a listing, including an excellent primer entitled "Evaluating Therapies
I & II".
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Answer: George
Carter responds- Hmmm...I don't think I buy the first part of the statement.
Break it down into white blood cells and red blood cells. Under white blood
cells, you have many lymphocytes, including T-cells. They develop from
hematopoietic progenitor cells into CD4+CD8+ and then, because they are
processed in the thymus (wherefore T-cells), they follow a course as either
CD4-CD8+ or CD4+CD8-. These cells then are the naive cells. When exposed
to antigen, they become "effector" cells. After the antigenic challenge
subsides, most undergo apoptosis.
Some remain as memory cells (debatably identified by either CD45RA {naive}
or RO {memory}).
T-cells can further be
divided by whether the T-cell receptor is composed of an alpha/beta chain
(most common) or gamma/delta (more in the mucosal regions). Most of these
g/d cells are CD8+.
Natural killer cells are
not processed in the thymus, I don't believe, so they're not technically
T-cells (although they're known as large granular lymphocytes). They're
characterized by CD16+56+ expression. Going by a marker isn't accurate
because macrophages can express CD4, but again, their maturation isn't
thymus-dependent. B-cells, of course, are bone-marrow derived. There's
also LAK cells.
Sometimes, T-cells are
defined by their function. CD8+ cells can be cytotoxic T lymphocytes (identifying
infected cells and killing them) or suppressor cells that appear to dampen
immune responses. But this issue is a bit murky, and some evidence exists
for CD4 cells operating with a suppressor function. This may have more
to do with cytokine expression patterns or idiotypic networks.
Finally, CD25 and CD38:
CD25, the IL-2 receptor, is not a specific T-cell marker, but more one
of activation marker found also on macrophages and B-cells. CD38 is similarly
found on thymocytes, activated T-cells and B-cells. It's an activation
marker (like HLA-DR) often found on CD8 cells --and indeed, Giorgi's work
suggests this can be a part of the immunopathogenesis. (Others, like Lubaki
et al., found CD8+CD38-DR-CTLs were more effective in keeping HIV load
lower. J AIDS 1999;22(1):19-30).
Editor's Note:
For additional information visit the following web sites- Glossary
of HIV/AIDS-Related Terms, T-cell
Tests, T-helper
Cells, and The
Immune System: Behind the Scenes.
Question: "Are
there any foods that are believed to help boost T-cells?"
Answer: Diana
Peabody, RD responds- There is no evidence that eating a specific food
will increase T-cells. However, an adequate nutrient-dense diet does provide
the building blocks for immune cells. Certain nutrients (e.g., beta carotene)
in foods have been shown to improve T-cells but at much larger doses than
is usually found in food. There are some theories about the potential benefits
of coconut and garlic, but the claims for these foods have not been adequately
studied, much less proven.
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