Porphyromonas gingivalis (P. gingivalis) is a major etiological agent associated withperiodontitis. This study aims to develop antibodies to P. gingivalis in vitro for real-time detection of bacteria in clinical samples. Lymphocytes were isolated from wholeblood of patient treated for periodontitis and were stimulated with P. gingivalis ATCC33277. B-cell maturation to long-living antibody secreting-plasma cells was studiedusing flow cytometry and immunofluorescence staining. The antibodies developedin vitro were immobilized onto a CM-5 sensor chip of a biosensor to detect the pres-ence of P. gingivalis in the gingival crevicular fluid of patients with periodontitis com-pared to periodontally healthy controls (n = 30). Surface plasmon resonance (SPR)analysis was performed to evaluate specific interactions of bacteria in samples withthe immobilized antibodies. The results of SPR analysis were compared to the detec-tion of P. gingivalis in the samples using DNA–DNA checkerboard hybridizationtechnique. A clear and distinct change in lymphocyte morphology upon stimulationwith P. gingivalis was observed. Anti-P. gingivalis antibodies secreted by CD38+plasma cells showed the presence of all the four IgG subclasses. The results ofDNA–DNA checkerboard analysis were in agreement with that of SPR analysis forthe detection of P. gingivalis in patient samples. Furthermore, incubation with anti-P. gingivalis attenuated the bacterial response in SPR. The in vitro method for antibodyproduction developed during this study could be used for an efficient real-time detec-tion of periodontitis, and the attenuating effects of in vitro antibodies suggest their rolein passive immunization to prevent periodontitis and their associated risk factors.