Specializing Early: T Cells as Rugrats of the Immune System
By Jason Socrates Bardi
In a comical scene from Ron Howard's 1989 movie "Parenthood",
Rick Moranis is reading Kafka to his three-year old daughter
at bedtime—probably to pad her application to nursery
school so that she can stand out in the highly competitive
world of pre-school.
Specializing early pays—so says Rick Moranis, and so
says the immune system.
A controversial new discovery by Louise and Michael McHeyzer-Williams
in the Department of Immunology at The Scripps Research Institute
suggests that helper T cells in the immune system specialize
earlier than was previously believed.
Helper T cells, also known by the CD4 protein marker on
their surface, are the master regulator of the adaptive immune
system, initiating and regulating the entire adaptive immune
response. Once activated by the recognition of an antigen,
the helper T cell will produce a swill of chemicals to clear
the infection and to attract and activate other immune cells,
like killer T cells and B cells.
Activated helper T cells are always one of two kinds—either
especially good at helping B cells or exceptionally good at
helping killer T cells. For years, the prevailing opinion
among scientists has been that helper T cells become specialized
into one of these two types after they are activated by antigen-presenting
dendritic cells.
But in an article that appears in the February issue of
the journal Immunity, the McHeyzer-Williamses show
that a division among helper T cells is preexisting and occurs
after the helper T cells develop in the thymus but before
they are activated in the periphery.
The McHeyzer-Williamses sorted mature, na•ve helper T cells
by looking at a specific marker protein called Ly6C expressed
on the surface of helper T cells. Activated mature helper
T cells that specialize in stimulating antibody production
by B cells show high expression of Ly6C on their surface.
After three days in the periphery, and with no stimulation
by the presence of antigen, the helper T cells the McHeyzer-Williamses
studied could already be divided into their two corresponding
phenotypic pools. When tested in vivo for their ability
to stimulate B cells, the helper T cells with high levels
of Ly6C expression were more adept at activating the B cells.
Now the McHeyzer-Williamses would like to know how the Ly6C
(high) helper T cells do their specialized job and how they
differ from the Ly6C (low) subset. It is also intriguing to
speculate on the pre-exisiting function of the Ly6C (low)
cells and to test their capacity to help killer T cells.
To read the article, "Developmentally Distinct Th Cells
Control Plasma Cell Production In Vivo" by Louise J. McHeyzer-Williams
and Michael G. McHeyzer-Williams, see the February 2004 issue
of the journal Immunity (231-242) or go to: http://www.immunity.com/content/article/abstract?uid=PIIS1074761304000287
Send comments to: jasonb@scripps.edu
|
