In situ PCR was applied to the paraffin embedded tissue section of two borderline tuberculoid patients which did not show acid fast bacilli on the Fite stain. In situ PCR was performed with direct detection of Digoxigenin incorporated into PCR product. The best condition of the direct in situ PCR was pretreatment with 0.2N HCl for 40 minutes and with 10㎍/ml of proteinase K at 37℃ for 5 minutes and 30 cycles of PCR. The positive signal was observed within the cytoplasm of the most Schwann cells, epithelioid cells and a few endothelial cells.

This study was planned to help the diagnosis of borderline leprosy by application of the in situ PCR. In situ PCR was performed in the tissue from skin biopsy using the Dig DNA probe synthesis kit®(Behringer Mannheim Co) on silanized slides and Dig incorporated PCR products were visualized by alkaline phosphatase conjugated anti-Dig antibody using NBT/BCIP as substrate. In the borderline lepromatous patients homogeneous or granular strong deposits were observed mainly within the cytoplasm of the histiocytes and proliferated Schwann cells. Some secretory cells of sweat glands, erector pile muscle and a few endothelial cells were weakly stained. In the tuberculoid leprosy patients no positive signal was observed. In conclusion in situ PCR can be applied on the tissue of berderline lepromatous patients of which sample does not need proteinase K treatment.