The function of high endothelial venules in mouse lymph nodes stimulated by oxazolone.

The effects of antigenic stimulation on the expansion of T-cell dependent areas in lymph nodes of mice were studied in relation to the effects on high endothelial venules (HEV) located in this area. Lymph nodes regional to areas of skin that had been treated with solutions of oxazolone were studied at several time-points after stimulation. The following measurements were made relative to lymph nodes of untreated animals: (i) the expansion of the T-cell dependent areas in combination with the increase of HEV in this area, as detected by the HEV-specific mAb MECA-325, using morphometric analysis: (ii) the influx of FITC-labelled lymphocytes from the blood into the lymph node by FACS: (iii) the capacity of HEV to bind lymphocytes using an in vitro binding assay. Morphometry showed that T-cell dependent areas increased rapidly after stimulation with oxazolone and although the mean area of MECA-325-positive HEV had also increased, this increase lagged behind the expansion of the T-cell area. Therefore the amount of HEV per T-cell area in an antigen-stimulated lymph node was smaller than in an untreated lymph node and correlated with the percentage of FITC-labelled cells that had entered it. In a lymph node from an oxazolone-treated animal this percentage was decreased to the same order of magnitude as the area of HEV per T-cell area, but the overall binding capacity of HEV was not affected by oxazolone treatment. Antigenic stimulation therefore leads to a rapid expansion of the potential sites of lymphocyte entry into a lymph node, but the efficiency of the HEV does not change.