Knisely T L, Hosoi J, Nazareno R, Granstein R D
MGH-Harvard Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital, Charlestown 02129.
Invest Ophthalmol Vis Sci. 1994 Sep;35(10):3711-23.
Immunosuppressive factors in aqueous humor (AH) contribute to the immune-privileged status of the anterior chamber of the eye. One such factor is transforming growth factor-beta (TGF-beta); other relevant inhibitors have not been fully identified. The authors examined AH to search for other putative inhibitors and to determine their effect on TGF-beta inhibitory activity.
Radioimmunoassays (RIA) were used to detect the presence of hydrocortisone, corticosterone, cortisol binding globulin (CBG), and alpha-melanocyte stimulating hormone (alpha-MSH) in AH. The ability of these factors to inhibit murine thymocyte proliferation stimulated by phytohemagglutinin-interleukin 1 (PHA/IL-1) and proliferation of a TGF-beta-sensitive cell line (CCL64) in vitro was examined. The ability of hydrocortisone to inhibit a one-way mixed lymphocyte reaction (MLR) and the ability of epidermal cells to present soluble tumor-associated antigens (TAA) for elicitation of immunity in mice in the concentration range present in AH was also examined.
Hydrocortisone was detected in mouse, rat, and human AH (10.8 +/- 1.1 ng/ml, 9.3 +/- 2.1 ng/ml, and 18.0 +/- 1.0 ng/ml, respectively; mean +/- SEM), as was corticosterone (2.7 +/- 0.9 ng/ml, 2.2 +/- 0.3 ng/ml, and 0.7 +/- 0.1 ng/ml, respectively). Whereas normal plasma contains a binding protein for corticosteroids (i.e., CBG), the concentration in mouse, rat, and human AH was less than the level detectable by an RIA. Hydrocortisone inhibited PHA/IL-1-stimulated murine thymocyte proliferation and CCL64 cell proliferation in the concentration range present in AH. When hydrocortisone was combined with TGF-beta 2 (125 pg/ml), the degree of inhibition observed was greater than with either alone. Corticosterone inhibited thymocyte costimulation only slightly at concentrations present in AH but was inhibitory for CCL64 cells. alpha-MSH was also detected in AH. The concentration present had only slight inhibitory effects for CCL64 cell proliferation and did not enhance TGF-beta 2-mediated (62 pg/ml to 250 pg/ml) inhibition of CCL64 or thymocyte proliferation. Hydrocortisone inhibited the one-way MLR in the concentration range present in AH and, at 10 ng/ml, inhibited the ability of epidermal cells to present TAA for elicitation of delayed-type hypersensitivity in tumor-immune mice.
These results show that AH contains biologically relevant concentrations of glucocorticoids and that CBG is relatively absent so that glucocorticoids present are largely free, and they suggest that regional sites take advantage of the activities of multiple factors to maintain an immune-privileged status.
房水中的免疫抑制因子有助于维持眼内前房的免疫赦免状态。其中一种因子是转化生长因子-β（TGF-β）；其他相关抑制剂尚未完全确定。作者检测房水以寻找其他可能的抑制剂，并确定它们对TGF-β抑制活性的影响。
采用放射免疫分析法（RIA）检测房水中氢化可的松、皮质酮、皮质醇结合球蛋白（CBG）和α-黑素细胞刺激素（α-MSH）的存在。检测这些因子在体外抑制植物血凝素-白细胞介素1（PHA/IL-1）刺激的小鼠胸腺细胞增殖以及TGF-β敏感细胞系（CCL64）增殖的能力。还检测了氢化可的松在房水浓度范围内抑制单向混合淋巴细胞反应（MLR）以及表皮细胞呈递可溶性肿瘤相关抗原（TAA）以引发小鼠免疫的能力。
在小鼠、大鼠和人房水中检测到氢化可的松（分别为10.8±1.1 ng/ml、9.3±2.1 ng/ml和18.0±1.0 ng/ml；平均值±标准误），皮质酮也被检测到（分别为2.7±0.9 ng/ml、2.2±0.3 ng/ml和0.7±0.1 ng/ml）。正常血浆含有一种皮质类固醇结合蛋白（即CBG），但小鼠、大鼠和人房水中的浓度低于RIA可检测水平。氢化可的松在房水浓度范围内抑制PHA/IL-1刺激的小鼠胸腺细胞增殖和CCL64细胞增殖。当氢化可的松与TGF-β2（125 pg/ml）联合使用时，观察到的抑制程度大于单独使用任何一种时。皮质酮在房水浓度下仅轻微抑制胸腺细胞共刺激，但对CCL64细胞有抑制作用。房水中也检测到α-MSH。其浓度对CCL64细胞增殖仅有轻微抑制作用，且不增强TGF-β2介导的（62 pg/ml至250 pg/ml）对CCL64或胸腺细胞增殖的抑制作用。氢化可的松在房水浓度范围内抑制单向MLR，且在10 ng/ml时，抑制表皮细胞呈递TAA以引发肿瘤免疫小鼠迟发型超敏反应的能力。
这些结果表明房水中含有具有生物学活性浓度的糖皮质激素，且相对缺乏CBG，使得存在的糖皮质激素大部分处于游离状态，这表明局部区域利用多种因子的活性来维持免疫赦免状态。
