Lack of evidence for an increased microchimerism in the circulation of patients with Sjögren's syndrome
- aInstitute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan, bDepartment of Ophthalmology, Tokyo Dental College, Japan
- Dr M Kuwana, Institute for Advanced Medical Research, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160–8582, Japan
- Accepted 15 May 2000
OBJECTIVE To examine the hypothesis that fetal microchimerism plays a part in the pathogenic process of Sjögren's syndrome (SS).
METHODS Genomic DNA samples were extracted from peripheral blood whole nucleated cells and the CD34+ cell enriched fraction of patients with SS and healthy women who had male offspring as well as nulliparous women. A Y chromosome-specific sequence was detected as a marker for fetal cells by a nested polymerase chain reaction (PCR) and by DNA hybridisation combined with PCR using specific primers and probes. All procedures were performed with great care to avoid the contamination of male DNA.
RESULTS A nested PCR and DNA hybridisation combined with PCR was established that can detect a single male cell out of 1.67×105 female cells. It was not possible to increase the sensitivity further because the amount of template DNA held in the PCR was limited. When these methods were used, no fetal cells were detected in any samples from patients with SS, though they were detected in whole nucleated cells from two healthy women who had delivered sons previously.
CONCLUSIONS The findings indicate that circulating fetal cells in patients with SS are uncommon ( < 1 in 1.67×105), if they exist. With the conventional PCR based methods that were used, it is difficult to evaluate the quantitative difference in circulating fetal cells between patients with SS and healthy women.
This work was supported by the grants from the Japanese Ministry of Health and Welfare and from the Japanese Ministry of Education, Science, and Culture.