Lack of correlation between chemokine receptor and Th1/Th2 cytokine expression by individual memory T cells

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Abstract
Chemokine and chemokine receptor interactions may have important roles in leukocyte migration to specific immune reaction sites. Recently, it has been reported that CXC chemokine receptor (CXCR) 3 and CC chemokine receptor (CCR) 5 were preferentially expressed on Th1 cells, and CCR3 and CCR4 were preferentially expressed on Th2 cells. To investigate chemokine receptor expression by Th subsets in vivo, we analyzed cytokine (IL-2, IL-4 and IFN-γ) and chemokine receptor (CXCR3, CXCR4, CCR3, CCR4 and CCR5) mRNA expression by individual peripheral CD4+ memory T cells after short-term stimulation, employing a single-cell RT-PCR method. This ex vivo analysis shows that the frequencies of cells expressing chemokine receptor mRNA were not significantly different between Th1 and Th2 cells in normal peripheral blood. To assess a potential role of in vivo stimulation, we also analyzed unstimulated rheumatoid arthritis synovial CD4+ memory T cells. CXCR3, CXCR4, CCR3 and CCR5 expression was detected by individual synovial T cells, but the frequencies of chemokine receptor mRNA were not clearly different between Th1 and non-Th1 cells defined by expression of IFN-γ or lymphotoxin-α mRNA in all RA patients. These data suggest that chemokine receptor expression does not identify individual memory T cells producing Th-defining cytokines and therefore chemokine receptor expression cannot be a marker for Th1 or Th2 cells in vivo.