Human cerebrospinal fluid contains CD4+ memory T cells expressing gut- or skin-specific trafficking determinants: relevance for immunotherapy

Abstract

Background: Circulating memory T cells can be divided into tissue-specific subsets, which traffic through distinct tissue compartments during physiologic immune surveillance, based on their expression of adhesion molecules and chemokine receptors. We reasoned that a bias (either enrichment or depletion) of CSF T cell expression of known organ-specific trafficking determinants might suggest that homing of T cells to the subarachnoid space could be governed by a CNS-specific adhesion molecule or chemokine receptor.

Results: The expression of cutaneous leukocyte antigen (CLA) and CC-chemokine receptor 4 (CCR4; associated with skin-homing) as well as the expression of integrin alpha4beta7 and CCR9 (associated with gut-homing) was analyzed on CD4+ memory T cells in CSF from individuals with non-inflammatory neurological diseases using flow cytometry. CSF contained similar proportions of CD4+ memory T cells expressing CLA, CCR4, integrin alpha4beta7 and CCR9 as paired blood samples.

Conclusion: The results extend our previous findings that antigen-experienced CD4+ memory T cells traffic through the CSF in proportion to their abundance in the peripheral circulation. Furthermore, the ready access of skin- and gut-homing CD4+ memory T cells to the CNS compartment via CSF has implications for the mechanisms of action of immunotherapeutic strategies, such as oral tolerance or therapeutic immunization, where immunogens are administered using an oral or subcutaneous route.

Figure 1

The majority of CD4+/CD45RA- memory T cells in the CSF (black bars) were CLA-/α4β7-, but discrete populations of CLA+ (associated with skin-homing) and integrin α4β7+ (associated with gut-homing) cells were observed. The expression pattern of CLA and integrin α4β7 was comparable on CD4+/CD45RA- memory T cells in peripheral blood (white bars) and CSF (black bars). Data are from four patients with non-inflammatory neurological diseases and figure shows mean+SEM.

Figure 2

Multi-color flow cytometry was used to analyze the co-expression of CCR4 with CLA or CXCR3 on memory T cells in paired blood and CSF samples from an individual patient with a non-inflammatory neurological disease (A-D) or MS (E-F). The expression of trafficking determinants was analyzed on CD4+/CD45RO+ memory T cells to account for the different percentages of naïve and memory CD4+ cells in blood (A) and CSF (B). As expected, there was an association between the expression of CCR4 and CLA on CD4+/CD45RO+ T cells in peripheral blood (C). A majority of CLA+ memory T cells co-expressed CCR4 also in the CSF, but some CCR4 staining could be detected on CLA- memory T cells (D). While a large population of CCR4+/CXCR3- cells, which have been demonstrated to be enriched for Th2 cells [27], were present in peripheral blood (E), such cells were rare in the CSF (F).

Figure 3

Flow cytometry was used to determine the expression of CCR9 and integrin β7, associated with homing to the gut, on CD4+/CD45RA- memory T cells in paired blood and CSF samples from patients with non-inflammatory neurological diseases. Memory T cells expressing CCR9 and integrin β7 were detected at comparable numbers in blood (A) and CSF (B), indicating that gut-homing memory T cells readily access the CNS.