Lymphocytes in inflamed tissues express numerous chemokine receptors. The relative importance of these receptors for migration in inflammation is unclear. The role of CXCR3 in T cell subset migration was examined using monoclonal antibodies developed to rat CXCR3. CXCR3 was expressed on sixfold more CD8 + (*30%) than CD4 + (*5%) T cells in spleen, lymph nodes and blood, and on *10% of CD4 + CD45RC -(memory) and *50% of CD8 + CD45RC + spleen T cells. After immunization, CXCR3 increased tenfold on CD4 + lymph node lymphoblasts (*55%), and >90% of inflammatory exudate T cells were CXCR3 + . CXCR3 + T cells migrated significantly better than CXCR3 -T cells to all dermal inflammatory stimuli tested in vivo, even though these T cells are a minority of the memory T cells. Blocking CXCR3 inhibited recruitment of 60-85% of unstimulated T cells and up to 90% of CD8 + CD45RC + effector T cells, but caused <50% inhibition of CD4 + and CD8 + memory (CD45RC -) T cells. About 90% of T lymphoblast migration to IFN-c, IFN-c plus TNF-a, polyinosinic polycytidylic acid, lipopolysaccharide, and delayed-type hypersensitivity (DTH)-induced inflammation was inhibited. Blockade also reduced DTH-induced induration. Thus, CXCR3 has a nonredundant role in T cell migration to dermal inflammation and is critical for activated T lymphoblast recruitment, but memory T cells are less dependent on CXCR3 for their infiltration.

CCR4 and CXCR3 are expressed on several T-cell subsets in inflamed tissues, yet their role in tissue-specific recruitment is unclear. We examined the contributions of CCR4 and CXCR3 to T-cell recruitment into inflamed joints in collagen-induced arthritis, antigendraining lymph nodes (LNs) and dermal inflammatory sites (poly I:C, LPS, concanavalin A, and delayed type hypersensitivity), using labeled activated T cells from CXCR3 −/− , CCR4 −/− , and WT mice. Both CXCR3 and CCR4 deficiency reduced the development of arthritis, but did not affect Th1-cell recruitment to the inflamed joints. Accumulation in inflamed LNs was highly CXCR3 dependent. In contrast, CCR4-deficient Th1 cells had an increased accumulation in these LNs. Migration to all four dermal inflammatory sites by activated Th1 and T cytotoxic cells and memory CD4 + T cells was partially CXCR3-dependent, but Treg-cell migration was independent of CXCR3. The subset of cells expressing CCR4 has skin-migrating properties, but CCR4 itself is not required for the migration. Thus, migration into these inflamed tissues is CCR4-independent, and partially dependent on CXCR3, except for Treg cells, which require neither receptor. CCR4 may therefore affect retention of T cells in different tissues rather than trafficking out of the blood.

CCR4 on T cells is suggested to mediate skin homing in mice. Our objective was to determine the interaction of CCR4, E-selectin ligand (ESL), and α4β1 on memory and activated T cells in recruitment to dermal inflammation. mAbs to rat CCR4 were developed. CCR4 was on 5–21% of memory CD4 cells, and 20% were also ESL+. Anti–TCR-activated CD4 and CD8 cells were 40–55% CCR4+, and ∼75% of both CCR4+ and CCR4− cells were ESL+. CCR4+ memory CD4 cells migrated 4- to 7-fold more to dermal inflammation induced by IFN-γ, TNF, TLR agonists, and delayed-type hypersensitivity than CCR4− cells. CCR4+ activated CD4 cells migrated only 5–50% more than CCR4− cells to these sites. E-selectin blockade inhibited ∼60% of CCR4+ activated CD4 cell migration but was less effective on memory cells where α4β1 was more important. Anti-α4β1 also inhibited CCR4− activated CD4 cells more than CCR4+ cells. Anti–E-selectin reduced activated CD8 more than CD4 cell migration. These findings modify our understanding of CCR4, ESL, α4β1, and dermal tropism. There is no strict relationship between CCR4 and ESL for skin homing of CD4 cells, because the activation state and inflammatory stimulus are critical determinants. Dermal homing memory CD4 cells express CCR4 and depend more on α4β1 than ESL. Activated CD4 cells do not require CCR4, but CCR4+ cells are more dependent on ESL than on α4β1, and CCR4− cells preferentially use α4β1. The differentiation from activated to memory CD4 cells increases the dependence on CCR4 for skin homing and decreases the requirement for ESL.

CCR4 is on T cells in dermal inflammation and may mediate homing to skin. Our objective was to determine the expression and interaction of CCR4, E-selectin ligand (ESL) and a4β1 on memory and activated T cells in recruitment to dermal inflammation. A mAb to CCR4 (CR4.1) was developed. CCR4 was on ~10% of memory CD4 cells and 15% of these were ESL+. CCR4 and ESL were markedly increased on activated T cells. CCR4+ memory CD4 cells (memCCR4+) migrated 8-10 fold more to inflammation induced by cytokines, TLR agonists and DTH, than memCCR4- cells, and homed less to LNs. CCR4+ anti-TCR activated CD4 cells (actCCR4+) migrated only 50% better to skin than actCCR4- cells. E-selectin blockade inhibited 50-75% of actCCR4+, but not memCCR4 cell migration. a4β1 blockade had an inverse effect, i.e. inhibiting memCCR4+ more than actCCR4+ cells, while P-selectin blockade had no effect. Thus, CCR4 is on a subset of memCD4 cells with dermal tropism, but this selective homing is reduced on activated CD4+CD25+cells. The role of ESL and a4β1 also differs between activated and memory CCR4+ cells, with a decrease in the role of ESL and an increase in a4β1 with differentiation to long-term memory. (Supported by the CIHR).