Figure 5

Suppression of NK-cell cytotoxicity by Con A-activated CD4⁺Foxp3⁻ T cells was Qa-1 dependent. (A) Anti-Qa-1 or anti-NKG2A antibody abrogated the suppression of activated CD4⁺ T cells on NK-cell cytotoxicity in vitro. Data shown are representative of three independent experiments. (B) Percentage of NKG2A-positive cells in the NK population. (C) Qa-1 antibody could reverse the inhibition of NK function by activated CD4⁺ T cells in vivo. SCID mice (n = 3/group) were injected with saline or Con A-activated CD4⁺Foxp3⁻ T cells (Act. T) or Act. T plus anti-mouse Qa-1 antibody. At the indicated times, cytolytic activities of splenocytes were determined ex vivo in a ⁵¹Cr release assay. (D) Metastatic nodules on the lung surface of animals treated with activated CD4⁺ T cells in the presence or absence of anti-Qa-1. Data were recorded as mean ± SD, and the Student's t test was used to compare between groups. (E) Photos of dissected lungs from the two groups (n = 5/group) in D. The visible melanoma nodules on the lung surface were significantly reduced in animals treated with anti-Qa-1 as compared with those non-treated. (F) Con A-activated T cells from Qa-1 knockout mice lost their inhibitory function on NK cytotoxicity in vitro. Data were mean ± SD, and representative of two independent experiments. (G) Con A-activated CD4⁺Foxp3⁻ T cells from Qa-1 knockout mice failed to facilitate B16 melanoma metastasis in RAG-1^−/− mice. Sex- and age-matched RAG-1^−/− mice were injected with B16 melanoma cells via tail vein one day before transferring resting or activated CD4⁺Foxp3⁻ T cells from wild-type or Qa-1 knockout mice. Ten days later, tumor metastasis was assessed by counting melanoma nodules on the lung surface. Error bars indicate mean ± SD (n = 6) and statistical significance was tested by Student's t test. (H) Photos of dissected lungs from the 4 groups (n = 6/group) in G. There was a significantly decreased number of visible melanoma nodules on the lung surface in Qa-1 knockout mice as compared with those wild-type animals.