Increased "in vivo" lymphocyte blastogenesis in the peripheral blood of patients with atopic dermatitis and allergic contact dermatitis.

The spontaneous 3H-thymidine (3HT) labelling of some lymphocyte subpopulations has been studied in the peripheral blood of five patients with atopic dermatitis and five with widespread allergic contact dermatitis and compared with that in 10 healthy subjects. One hour after addition of 3HT to heparinized blood, lymphocytes were separated and processed with two different rosetting techniques (E-rosette test and Active E-rosette test). The cell suspensions were cytocentrifugated and autoradiography undertaken. An increased number of 3HT labelled lymphocytes was observed in the peripheral blood of patients with dermatitis as compared to controls. These labelled lymphocytes were E-rosette-forming cells (T cells) and E-non-rosette-forming cells (non-rosette-forming T cells and non-T cells). The ratio between the labelling index (LI) of E-rosette- to the LI of non-E-rosette-forming cells was in favour of T cells in allergic contact dermatitis (ratio = 3.09) whereas in atopic dermatitis (ratio = 0.93) the DNA synthesis was relatively greater in the non-rosette-forming cells. It is suggested that this increased LI of peripheral blood lymphocytes could be related to the increased derman mononuclear cell 3HT-labelling that has been reported previously in these inflammatory skin diseases.