Gold allergy : In vitro studies using peripheralblood mononuclear cells

Sammanfattning: Positive patch test reactions to gold are commonly seen in dermatology clinics, but it is veryunusual for the patients to actually have any clinical symptoms. It is also common with irritantreactions that are not linked to adaptive immunity. Therefore, a deeper understanding of themechanisms underlying allergic contact dermatitis (ACD) reaction, and the search for acomplementing diagnostic tool, is important.In paper I we included three subject groups; one with morphologically positive patch testreactions to gold sodium thiosulphate (GSTS, the gold salt used in patch testing), one withnegative patch tests, and one with irritant reactions to gold. Blood samples were collected andexamined regarding the proliferation rate and which cytokines were secreted after culturingwith GSTS. We saw that the cultured lymphocytes from the allergic donors proliferated at asignificantly higher rate than the two other subject groups, and that the cells secreted cytokinesof both Th1 (Interferon (IFN) -g and Interleukin (IL) -2) and Th2 (IL-13 and IL-10) types. Theallergic donors secreted significantly higher levels of IFN-g, IL-2 and IL-13 than the two othersubject groups. Both the negative and irritant subject groups showed suppressed levels of thecytokines as compared with the unstimulated cultures, demonstrating the immunosuppressingeffects of gold.We also examined whether any of the analyzed markers, alone or combined, could be usedas an aid for diagnosing ACD to gold. We found that the IFN-g assay yielded the highestsensitivity (81.8 %) and specificity (82.1 %), and also identified 87.5 % of the irritant group asnon-allergic.In paper II we decided to investigate what cell types and subsets that reacted to the goldstimulation. We analyzed proliferation rate and expression of CD45RA, CD45R0, cutaneouslymphocyte-associated antigen (CLA) and the chemokine receptors CXCR3, CCR4 andCCR10. Similar to what has previously been published about nickel (Ni) allergy, the cells fromthe gold-allergic subjects that reacted to the GSTS stimulation expressedCD3+CD4+CD45R0+CLA+. However, contrary to findings in studies on Ni-reactive cells, wesaw no differences between allergic and non-allergic subjects regarding any of the chemokine receptors studied.In conclusion, we found that analysis of IFN-g might be a useful complement to patchtesting, possibly of interest in avoiding the need for repeated tests to rule out irritant reactions.We also saw that the cells that proliferated in response to gold were memory T-cells expressingCD4 and CLA, the marker for skin-homing. However, these cells did not express elevatedlevels of any of the chemokine receptors analyzed, showing that there are both similarities anddifferences between the mechanisms for Ni allergy and gold allergy.