Effect of metal allergens on the DNA synthesis of unsensitized guinea pig lymphoid cells cultured in vitro.

The metal allergens cobalt chloride, mercuric chloride, nickel sulfate and potassium dichromate were tested regarding their effect on the DNA synthesis of lymphoid cells from unsensitized guinea pigs. At certain concentrations in the range of 10(-8) to 10(-6) M, all tested metal compounds stimulated the DNA synthesis of both thymocytes and peripheral lymphocytes after 48 h of culture. The most consistent stimulation with all tested metal allergens was obtained with spleen cells. Thymocytes and spleen cells were stimulated even when the small fraction of adherent cells was eliminated. Mercuric chloride and potassium dichromate were found to be inhibiting at 10(-6) to 10(-4) M, while cobalt chloride and nickel sulfate were less toxic and inhibiting at 10(-4) to 10(-3) M. At 5 h of culture the lowest inhibitory concentration of potassium dichromate was found to be about 100-fold lower than that of nickel sulfate, which may be of practical interest for the choice of concentrations used in human patch test. The lowest concentrations of mercuric chloride and potassium dichromate which at 5 h were inhibitory, were stimulating at 48 h. The presence of serum seemed to have a protective and modifying role regarding the effect of the various metal compounds on the DNA synthesis.