Loss of CCR7 Expression on CD56brightCD56^{bright} NK Cells Is Associated with a CD56dimCD16+CD56^{dim}CD16^{+} NK Cell-Like Phenotype and Correlates with HIV Viral Load

NK cells are pivotal sentinels of the innate immune system and distinct subpopulations in peripheral blood have been described. A number of studies addressed HIV-induced alterations of NK cell phenotype and functionality mainly focusing on $CD56^{dim}CD16^{+}$ and $CD56^{-} CD16^{+}$ NK cells. However, the impact of HIV-infection on $CD56^{bright}$ NK cells is less well understood. Here we report a rise of $CD56^{bright}$ NK cells in HIV-infected individuals, which lack CCR7-expression and strongly correlate with HIV viral load. $CCR7^{−} CD56^{bright}$ NK cells were characterized by increased cytolytic potential, higher activation states and a more differentiated phenotype. These cells thus acquired a number of features of $CD56^{dim}CD16^{+}$ NK cells. Furthermore, $CD56^{bright}$ NK cells from HIV patients exhibited higher degranulation levels compared to uninfected individuals. Thus, chronic HIV-infection is associated with a phenotypic and functional shift of $CD56^{bright}$ NK cells, which provides a novel aspect of HIV-associated pathogenesis within the NK cell compartment

HIV Infection Is Associated with a Preferential Decline in Less-Differentiated CD56dim CD16+ NK Cells▿

HIV-1 infection is characterized by loss of CD56dim CD16+ NK cells and increased terminal differentiation on various lymphocyte subsets. We identified a decrease of CD57− and CD57dim cells but not of CD57bright cells on CD56dim CD16+ NK cells in chronic HIV infection. Increasing CD57 expression was strongly associated with increasing frequencies of killer immunoglobulin-like receptors (KIRs) and granzyme B-expressing cells but decreasing percentages of cells expressing CD27+, HLA-DR+, Ki-67+, and CD107a. Our data indicate that HIV leads to a decline of less-differentiated cells and suggest that CD57 is a useful marker for terminal differentiation on NK cells

Relative and absolute loss of CCR7⁺CD56^bright NK cells is not attributable to apoptosis.

<p>(A) Absolute cell numbers of CD56^bright NK cells are depicted. Horizontal bars indicate means. (B) Absolute cell numbers of either CCR7⁺ or CCR7⁻CD56^bright NK cells are shown. (C) Representative flow cytometry data of CD95 on gated CD56^bright NK cells and respective summary data derived from untreated HIV-patients. Numbers in flow cytometry plots indicate frequencies of quadrants and horizontal bars in dot plot indicate mean values. (D) Pearson’s correlation analysis between frequencies of CCR7- and CD69-expressing CD56^bright NK cells. *, <i>P</i><0.05; ***, <i>P</i><0.001; <i>NS</i> – not significant.</p

Functional differences between CCR7

<p>⁻<b>and CCR7⁺CD56^bright NK cells from HIV-infected donors indicate high activation states.</b> (A) Representative flow cytometry plots of granzyme B and perforin expression on gated CD56^bright NK cells and summary data including CD56^dimCD16⁺ cells, from untreated HIV-infected subjects. Horizontal bars in dot plots show mean values. Numbers in corners represent percentage of quadrant. (B) Representative histograms and summary data of CD107a degranulation in CD56^bright cells from uninfected controls, untreated and HAART-treated HIV-patients. Data was generated using sorted NK cells stimulated with IL-12, IL-15 and K452 cells. (C) Representative flow cytometry plot of CD107a degranulation on gated CD56^bright NK cells and summary data of degranulation in CCR7⁺CD56^bright, CCR7⁻CD56^bright and CD56^dim NK cells from untreated HIV-infected subjects is shown. Data was generated using whole PBMCs stimulated with IL-12, IL-15 and K562 cells. Numbers in corners represent percentage of quadrant. (D) Spontaneous expression of IFN-γ in medium-only treated NK cell subsets is shown in a representative flow cytometry plot and a summary data graph. Data from untreated HIV-positive patients is shown and numbers in corners indicate percentages of quadrants. (E) Representative Ki-67-expression data and summary data on gated CCR7⁺ or CCR7⁻ CD56^bright cells and respective summary data including CD56^dimCD16⁺ NK cells from untreated HIV-seropositive subjects. Numbers in flow cytometry histogram plots indicate percentage of gated events. ***, <i>P</i><0.001; <i>NS</i> – not significant.</p

CCR7⁻CD56^bright NK cells exhibit phenotypic features of CD56^dimCD16⁺ cells.

<p>Representative expression data of CD62L, NKG2A, CD27, KIR3DL1, CD69 and CD16 on gated CCR7⁺ or CCR7⁻ CD56^bright cells and respective summary data including CD56^dimCD16⁺ NK cells, from untreated HIV-seropositive individuals. Numbers represent percentages of gated events and horizontal bars in dot plots indicate mean values. *, <i>P</i><0.05; **, <i>P</i><0.01; ***, <i>P</i><0.001.</p

Summary of demographical data of study participants.

<p>The profiles of all study participants are shown in a summary.</p

Loss of CCR7-expressing CD56^bright NK cells correlates with clinical disease markers.

<p>(A) Representative flow cytometry plots defining CD56^bright NK cells. Numbers indicate percentage of the gated population. (B) Representative CCR7, CD62L, CXCR3 and CD16 expression data and summary data all gated on CD56^bright NK cells. Horizontal bars in dot plot indicate mean values. (C) Pearson’s correlation analysis between frequencies of either CD62L⁺ or CD16⁺CD56bright NK cells and CCR7⁺CD56^bright NK cells in untreated HIV-seropositive patients. (D) Pearson’s correlation analysis between frequencies of CCR7⁺, CD62L⁺, CXCR3⁺ or CD16⁺ cells of total CD56^bright NK cells with either viral load or CD4⁺ T cell counts in untreated HIV-positive subjects. *, <i>P</i><0.05; ***, <i>P</i><0.001; <i>NS</i> – not significant.</p