Ihan Hren 1, N., Gubina 2, M.*, Ihan 2, A.,
1 Clinic for Maxilofacial and Oral Surgery, University Clinical Centre Ljubljana, Zaloška 7, 1000 Ljubljana 2 Institute for Microbiology and Immunology, Medical Faculty Ljubljana, Zaloška 4, 1000 Ljubljana, SLOVENIA.

21 dental periapical lesions were investigated in order to study bacterial colonisation. Periapical lesions, obtained after apicotomy were also enzymatically desegregated in order to quantitatively analyse lymphocyte subpopulations by flow cytometry. 16 samples yielded a positive bacterial growth when homogenised and cultured. We isolated enough lymphocytes to make flow cytometric analysis from 15 samples. A significant increase in IL-2 receptor and ICAM-1 molecule expression on T cells were found compared to peripheral blood lymphocytes. Furthermore, an increased expression of IL-2 receptors and HLA DR molecules on CD8+ T cells, as well as increased expression of intracellular interferon gamma by CD4+ T cells was found in granulomas predominantly colonised by strict anaerobes compared to lesions predominantly colonised Streptococcus sp. Our results suggest that strict anaerobes (Veillonella sp., Actinomyces sp., Bacterioides sp., Propionobacterium acnes) in periapical lesions may have an increased tendency to induce Th2- type cytotoxic immune response compared to oral streptococci (S. intermedius, S. sanguis, S. salivarius).