[en] The authors have recently demonstrated in vitro proliferation of mouse Thy-1⁺ dendritic epidermal cells (EC) to Con A and IL-2. The purpose of the present study was to utilize limiting dilution analysis to determine the precursor frequency (PF) of Con A-responsive cells within EC enriched by Isolymph centrifugation for Thy-1⁺ cells (IEC). AKR IEC were cultured in 96 well U-plates (25-75 cells/well) with 2 μg/ml Con A and 2 x 10⁵ irradiated (1600 R) AKR spleen cells/well. Cultures were harvested after 7-21 days following ³H-thymidine pulsing. Results indicated a PF within IEC of 1.5-4.5%. Inclusion of 10 U/ml IL-2 enhanced significantly the proliferation in positive wells but did not alter this PF. In AKR mice, monoclonal antibody 20-10-5S has been shown to react with Thy-1⁺ EC, but not with peripheral T cells. FACS purification of IEC using 20-10-5S indicated that Con A responsiveness resides exclusively within the 20-10-5S⁺ population. The PF of Con A-responsive Thy-1⁺ EC was calculated by dividing the PF of IEC by the fraction of 20-10-5S⁺ cells (13-30%) in the IEC suspension. A significant proportion of Thy-1⁺ EC (∼12%) were found to possess Con A proliferative capacity. These studies will facilitate analysis at a clonal level of possible functional and phenotypic heterogeneity within the Thy-1⁺ EC population

[en] Recently the authors reported that Con A stimulates in vitro proliferation of Thy-1+ dendritic epidermal cells (EC). They have not investigated the capacity of Con A-stimulated Thy-1+ EC to secrete IL-2-like activity (IL-2) 7-17EC is a 4 month-old line of Thy-1+ EC established from AKR/J EC by repeated stimulation with Con A and IL-2; these cells were 99% Thy-1+, but <1% L3T4+ and only 4-10% Lyt-2+. 7-17EC were harvested, washed, and plated in 96-well U-plates. Proliferation was assayed after 3H-thymidine pulsing; culture media was tested for IL-2 using the IL-2-dependent HT-2 cell line. With continuous Con A, marked IL-2 secretion (day 2 peak) was followed in parallel by proliferation (day 4 peak). In the absence of Con A, neither IL-2 nor proliferation was seen; however, both were recovered by addition of Con A to cells cultured first for 48 hr in media alone. 7-17EC proliferation was maximal at 0.5-2 μg Con A while maximal IL-2 secretion (100-200 U/ml) was seen at 4-8 μg/ml. That this amount of IL-2 was in excess of that required for their own optimal proliferation was supported by the failure of additional recombinant IL-2 (10 U/ml) to enhance Con A-stimulated proliferation of 7-17EC over a 4 day period. These findings further document the wide range of immunologic capabilities of Thy-1+ cells derived from epidermis