Human virus-specific effector-type T cells accumulate in blood but not in lymph nodes.

It is believed that the size of the CD8(+) T-cell pool is fixed and that with every new viral challenge, the size of the pre-existing memory-cell population shrinks to make way for the new virus-specific cells. CMV-seropositive individuals have high numbers of CMV-specific resting-effector type CD8(+) T cells in their peripheral blood (PB). This prompted us to investigate whether CMV infection limits immunologic space at sites where immune reactions are initiated, such as in the lymph nodes (LNs). LN and paired PB samples were analyzed for CMV-, EBV-, and influenza-specific CD8(+) T cells. In marked contrast to blood, LNs contained significantly lower numbers of CX3CR1-expressing effector-type CD8(+) T cells, whereas the CMV-specific cells that were found in the LNs resembled polyfunctional memory-type cells. In contrast, EBV- and influenza-specific CD8(+) T cells were highly similar between PB and LNs both in number and function. Therefore, it is unlikely that CMV-specific CD8(+) T cells in the LNs restrain the immunologic space of other virus-specific cells.