Saliva leukocytes rather than saliva epithelial cells represent the main source of DNA

Introduction. Several alternative methods to peripheral blood DNA extraction have been implemented so far. Saliva seems to represent a very advantageous type of sample, easy to harvest and able to generate DNA yields comparable to those extracted from blood mononuclear cells. Material and methods. 8 patients suspected of ankylosing spondylitis, 9 patients with various hematological malignancies, displaying post-chemotherapy leucopenia and 30 healthy volunteers were included in our study. DNA was extracted with various commercially available kits and used for HLA typing either by PCR amplification, or by PCR followed by hybridization. Results. Our data regarding HLA typing support already published results regarding the good DNA quality that allows its use in various molecular biology techniques. However, when attempting to use saliva from immunosuppressed patients for DNA extraction we have generated very low yields, comparable again with the ones obtained from peripheral blood. Flow cytometry and immunocytochemistry investigations confirmed the low number of leukocytes present in the saliva of these patients, while the number of epithelial cells was virtually unchanged. Conclusions. The main source of saliva DNA seems to be represented by leukocytes present in this fluid and not by the epithelial cells. Under these circumstances, for immunosuppressed patients saliva cannot represent an alternative to blood when attempting DNA extraction.