Expression and Function of TLR2 on CD4 Versus CD8 T Cells.
BACKGROUND
Toll-like receptors (TLRs) play a fundamental role in innate immunity through their capacity to recognize pathogen-associated molecular patterns. Also, TLRs that are expressed in T cells are reported to function as co-stimulatory receptors. However, the functional capacity of TLRs on CD4 T and CD8 T cells has not been directly compared. Here we compared CD4 and CD8 T cell responses to TLR2 ligand plus TCR-mediated stimulation.


METHODS
TLR2 expression was analyzed on T cell subsets under naïve and alloantigen-primed conditions. We analyzed the effects of TLR2 co-stimulation on proliferation and survival of T cell subsets in vitro when stimulated with soluble anti-CD3 in the presence or absence of synthetic ligand Pam(3)CSK(4).


RESULTS
TLR2 expression on CD8 T cells was induced following activation; this expression was much higher than on CD4 T cells. Thus, the molecule was constitutively expressed on Listeria-specific memory CD8 T cells. Based on these expression levels, proliferation and survival were markedly elevated in CD8 T cells in response to the TLR2 co-stimulation by Pam(3)CSK(4) compared with those in CD4 T cells.


CONCLUSIONS
Our data show that TLR2 co-stimulation is more responsible for proliferation and survival of CD8 T cells than for that of CD4 T cells.
Lee
Sun-Mi
SM
Department of Microbiology and Immunology, College of Medicine, Inje University, Busan 614-735, Korea.
Joo
Young-Don
YD
Seo
Su-Kil
SK