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Abstract
<p class="first" id="d23805571e55">In recent years, the phenotypic characterization
of T cell subsets has given way to
a functional dichotomy based essentially on their cytokine profiles. In this context,
the CD4+ helper T cell subset has been shown to consist of two types, termed Th1 and
Th2. In general, Th1 cells produce interleukin (IL)-2 and interferon (IFN)-gamma,
while Th2 cells characteristically produce IL-4, IL-5, and IL-6. The major function
of the Th1 subset is to mediate delayed-type hypersensitivity reactions and their
secondary function is suppression of B cell activity. In contrast, the major function
of the Th2 subset is to provide B cell help, while their secondary function is cell-mediated
immune suppression. A similar dichotomy has also been described for CD8+ T cells.
The role that these functional T cell subsets and their cytokines play in terms of
their protective and nonprotective outcomes in a variety of infectious and oral diseases
is reviewed.
</p>