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The effect of gold trichloride on DNA synthesis of human thymocytes and peripheral blood lymphocytes was tested. A stimulation was obtained in both cell types with a concentration of 6–50 μg/ml. Gold trichloride may thus not be used in a lymphocyte transformation test for the diagnosis of contact allergy. Correspondence to: Dr. Klas Nordlind, Department of Dermatology, Karolinska Sjukhuset, S–104 01 Stockholm (Sweden) Gold salts are potentially strong sensitizers in vivo as shown by the maximization test [6]. Most gold salts also seem to be irritant [2]; gold chloride can easily give a false-positive reaction in patch testing [4]. In vitro cultured peripheral blood lymphocytes have been shown to be inhibited in their mitogenic lectinand antigen-induced DNA synthesis by sodium aurothiomalate and gold trichloride [1, 7]. On the other hand, Schöpfet al. [11] reported a specific in vitro stimulation of peripheral blood lymphocyte DNA synthesis in a patient with a positive epicutane-ous reaction to gold trichloride, and Denman and Denman [3] got a positive lymphocyte transformation in patients with adverse effects after therapy with sodium aurothiomalate. In previous investigations [8, 10], mercuric chloride, in contrast to cobalt chloride and potassium dichromate, was shown to stimulate the DNA synthesis in human thymocytes, thereby eliminating its use in the lymphocyte transformation test for detection of contact sensitivity. In the present investigation the potential stimulating effect of gold trichloride on DNA synthesis was tested in human thymocytes and peripheral blood lymphocytes. Gold trichloride (HAuCL3⁄8 · aq.; Fluka, Switzerland) was prepared to a final concentration in the cultures of 1.5–100 μg/ml. Thymocytes were obtained from children undergoing heart surgery and peripheral blood lymphocytes from healthy adult donors without gold allergy. The different lymphocytes were separated on Percoll (density 1.129 g/ml; Pharmacia, Uppsala, Sweden) gradients on the basis of buoyant density [5, 8, 9]. Thymocytes with characteristics of medullary cells (mitogenic lectin-reactive) and peripheral blood lymphocytes were then resuspended in culture medium RPMI 1640 with addition of L-gluta-mine (2 μmol/ml), streptomycin (100 μg/ml), penicillin (100 IU/ml) and 15% heat-inactivated human AB serum to a concentration of 2×106 cells/ml. The thymocytes were incubated for 3 days and the peripheral blood lymphocytes for 6 days, in 100-μl culTable I. DNA synthesis stimulating effect of gold trichloride in thymocytes and peripheral blood lymphocytes The effect of different concentrations (μg/ml culture medium) of gold trichloride on the incorporation of tritiated thymidine in DNA of thymocytes and peripheral blood lymphocytes, D ow nl oa de d by : 54 .7 0. 40 .1 1 11 /1 8/ 20 17 9 :4 1: 47 P M incubated for 3 and 6 days, respectively, was tested. The activity in lymphoid cells from 5individuals is given as percentage of the control (mean ± SEM) and for the control also in cpm(mean ± SEM) (in parentheses). ND = Not done.460Nordlind tures, in a Linbro microtitration plate at 37 °C in an atmosphere of 5 % CO2 in air. After apreincubation for 30 min, 20 μl of the gold trichloride solution or 20 μ\ of saline was added. 6 hbefore interrupting the cultures, 0.5 μCi of 3H-thymidine (5 Ci/mmol; Radio-chemical Centre,Amersham) in lOμl saline was added to each well. The cells were then collected on a Skatronmultiple-cell collector using glass fiber filters. Incorporated radioactivity was determined bycounting in a Packard liquid scintillation spectrometer. The cultures were performed in triplicate.An evident DNA synthesis stimulation was obtained in both lymphoid cell types with a goldtrichloride concentration of 6–50 μg/ml (table I) while the highest concentration, 100 μg/ml, wasinhibitory. The stimulation degree was of the same magnitude in the thymocytes and peripheralblood lymphocytes. This is in contrast to the findings with mercuric chloride [8] and mightindicate another mechanism for the stimulation. However, this stimulation excludes thepossibility to use a lymphocyte transformation test for the diagnosis of gold trichloride contactallergy.ReferencesCahill, R.N.P.: Effect of sodium aurothiomalate ‘myocrisin’ on DNA synthesis inphytohaemagglutinin-stimulated cultures of sheep lymphocytes. Experientia 27: 913–914(1971).Cronin, E.: Contact dermatitis, p. 334 (Churchill Livingstone, Edinburgh 1980).Denman, E.J.; Denman, A.M.: The lymphocyte transformationtest and gold hypersensitivity. Ann. rheum. Dis. 27: 582–589 (1968).Fregert, S.; Kollander, M.; Poulsen, J.: Allergic contact stomatitis from gold dentures. ContactDermatitis 5: 63–64 (1979).Goust, J.M.; Perry, L.R., Jr.: Separation of human thymocytes at different stages of maturationby centrifugation on a discontinuous gradient of colloidal silica gel. Thymus 3: 25–33 (1981).Kligman, A.M.: The identification of contact allergens by human assay. III. The maximizationtest: a procedure for screening and rating contact sensitizers. J. invest. Derm. 47: 393–409(1966).Lipsky, P.E.; Ziff, M.: Inhibition of antigenand mitogen-in-duced human lymphocyteproliferation by gold compounds. J. clin. Invest. 59: 455–466(1977).Nordlind, K.; Henze, A.: Stimulating effect of mercuric chloride and nickel sulfate on DNAsynthesis of thymocytes and peripheral blood lymphocytes in children. Int. Archs Allergy appl.Immun. 73: 162–165(1984).Nordlind, K.: Fractionation of human thymocytes and peripheral blood lymphocytes on Percolldensity gradients and DNA synthesis stimulating effect of mercuric chloride. Int. Archs Allergyappl. Immun. 75: 16–19(1984). Nordlind, K.; Henze, A.: Investigation of ability of the metal allergens cobalt chloride, nickelsulfate and potassium dichro-mate to give a mitogenic response in human thymocytes. Int. ArchsAllergy appl. Immun. 75: 330–332(1984).Schöpf, E.; Wex, O.; Schulz, K.H.: Allergische Kontaktstomati-tis mit spezifischerLymphocytenstimulation durch Gold. Haut-arzt27: 422–424(1970). Downloadedby: 54.70.40.11-11/18/20179:41:47PM