Objective: The aim of the study was to examine if HPSE-1, the enzyme for modification of HS GAG chains, could be considered as a regulator of inflammatory response in advanced generalized periodontitis. Materials and methods: For the purpose of the study, the samples of healthy gingiva (controls; n = 20) and diseased gingiva from patients diagnosed with advanced generalized periodontitis (test group; n = 20) were taken and processed for immunhistochemistry (H/E staining and immunofluorescence). For immunofluorescence, the primary antibodies against HPSE1 and general inflammatory cell marker CD45 were applied. Quantification of various staining properties (histomorphometric parameters of gingival tissue, expression domains and intensity gradients of immunofluorescence staining) was performed on high-resolution panoramic images by using AdobePhotoshop® CC and ImageJ (image editing), as well as Microsof Office Excel® 2016 (Microsoft Corp, Redmond, WA, USA) and GraphPad v8 (GraphPad Software, La Jolla, CA, USA) for statistical analysis. Results: The expression of HPSE1 in healthy and diseased gingiva displayed statistically significant difference. The expression of HPSE1 was negatively correlated with the presence of inflammatory infiltrate in subepithelial stroma of both healthy and diseased gingiva. On the other hand, the expression of HPSE1 was correlated positively with specific structural changes in diseased gingiva (total and stromal celularity). Conclusion: HPSE1 could be considered as a regulator of inflammatory response in advanced generalized periodontitis. Modulation of enzymatic activity of HPSE1 could be exploited in the future as a possible approach for treatment of advanced generalized periodontitis. However, further studies are still needed in order to fully elucidate the scope of regulatory roles of HPSE1 in pathogenesis of advanced generalized periodontitis