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NK-Dependent Increases in CCL22 Secretion Selectively Recruits Regulatory T Cells to the Tumor Microenvironment
Journal article   Peer reviewed

NK-Dependent Increases in CCL22 Secretion Selectively Recruits Regulatory T Cells to the Tumor Microenvironment

Adam W. Mailloux and M. Rita I. Young
The Journal of immunology (1950), Vol.182(5), pp.2753-2765
03/01/2009
DOI: 10.4049/jimmunol.0801124
PMCID: PMC3337694
PMID: 19234170

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Abstract

Tumor-induced immune suppression involves the accumulation of immune-suppressive infiltrates in the microenvironment. This study demonstrates increased numbers of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) in the lungs of C57BL/6 mice hearing it metastatic Lewis lung carcinoma (LLC) variant. These Tregs suppressed the proliferation of endogenous CD4(+)CD25(-) cells and expressed higher levels of the chemokine receptor CCR4 than other types of T cells. LLC-bearing lungs secreted elevated levels of the CCR4-associated chemokine CCL22 compared with normal lungs. However, CCL22 was not secreted by LLC or normal epithelial controls, suggesting that CCL22 is secreted fly a nonepithelial component of the microenvironment. Migration assays revealed that medium conditioned by LLC-bearing lungs selectively recruited Tregs at higher frequencies than did medium conditioned by normal lungs. Neutralization or CCL22 significantly reduced this selective recruitment toward both conditioned media. A series of immunomagnetic isolations, FACS, and flow cytometric analyses were used to isolate different cellular fractions from both normal and LLC-bearing lungs. When isolated, only the NK-containing fractions secreted CCL22, and the same fraction isolated from LLC-bearing lungs secreted higher levels. Depletion of INK cells from both normal and LLC-bearing lung tissue significantly reduced CCL22 secretion, suggesting that a large portion of secreted CCL22 is NK cell dependent. Flow cytometric analysis of the lung NK compartments revealed no significant increase in NK cell numbers across LLC-bearing lung tissue as a whole as compared with normal tissue. However, immunofluorescent staining revealed an increased frequency of NK cells at the tumor periphery that were closely associated with the elevated FoxP3(+) infiltrate. The Journal of Immunology, 2009, 182: 2753-2765.
Immunology Life Sciences & Biomedicine Science & Technology

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