Another limitation of the present study is that GCF hCAP18/LL-37 levels were not evaluated in the same GCF samples in which proteinase 3 and cathepsin C levels were analyzed in order to test our hypothesis. In vitro studies searching the effect of these enzymes on each other and hCAP18 in neutrophils obtained from the patients with different periodontal diseases would supply important data for enlightening the possible deficiencies in neutrophils of these patients. Here, CTSC is linked to periodontal disorder.