Aqueous humor inhibits epidermal cell antigen-presenting function

Aqueous humor (AH) is a complex biological fluid containing factors that mediate a number of activities that may contribute to immune privilege in the anterior chamber of the eye. To determine whether AH may inhibit dendritic cell antigen-presenting function, we evaluated the ability of AH to alter the ability of freshly obtained epidermal cell (EC) preparations enriched for Langerhans cells (LC) to present tumor-associated antigens (TAA) derived from the S1509a spindle cell tumor for elicitation of a delayed-type hypersensitivity (DTH) reaction in tumor-immune mice. Fresh EC preparations contain 2-5% LC. Exposure of EC to media containing AH for 2 hours prior to TAA-pulsing and injection into a hind footpad of tumor-immune mice resulted in a dose-dependent decrease in the DTH response. Aqueous humor contains transforming growth factor-beta (TGF beta), primarily TGF beta 2 as determined by specific neutralization of activity in the Mv 1 Lu cell assay. However, exposure of EC to TGF beta 2 in this fashion prior to TAA-pulsing had no effect on the degree of hypersensitivity elicited. Furthermore, preincubation of AH with neutralizing antiserum to TGF beta 2 had no effect on the ability of AH to inhibit LC antigen-presenting function. Mixing of AH-exposed non-TAA-pulsed EC with TAA-pulsed EC not exposed to AH prior to footpad challenge did not diminish the DTH response, suggesting that carryover of AH into the footpad was not responsible for the inhibition observed.(ABSTRACT TRUNCATED AT 250 WORDS)