Introduction:
Oral polymorphonuclear neutrophils are also known by the short form oPMNs. These are basically the important and innate immune cells that are found in the oral cavity. Just like the PMNS (polymorphonuclear neutrophils), which are the active and the most abundant cellular form or component of the host or human immune system, the oPMNs that are found in the gingival fluid play a role in oral immunity.
What Are Oral Polymorphonuclear Leukocytes (oPMNs)?
The human oral cavity is responsible for the majority of functions like speech, chewing, tongue movements, and swallowing. However, it is a distinct entity from the other barrier sites in the human body. It can be susceptible to or invaded by microbial organisms in the state of inflammation or gingival or periodontal diseases. In the mouth, the barriers of microbial invasion are usually the oral mucosal surfaces that in fact cover the jaws, the cheeks, and the tongue. Current dental research logically focuses on the importance of oral PMNs in gingival and periodontal disease or inflammation holds crucial value in modern-day dentistry. This is because the most vulnerable site in the oral cavity in dental or periodontal patients is indeed the epithelium of the gingival crevices that surround the teeth. This is one of the major locations not only for the oPMNs to enter or exit the oral cavity, but also holds true for the infectious or anaerobic microorganisms that may colonize the oral cavity. These too have the same site as the port of entry.
What Are the Functions of oPMNS?
PMNs are critically needed in order to maintain the function and balance of the oral microbiome at the gingival barriers. The PMNs are the primary mediators of innate immunity in the body and the function of these white blood cells is to respond to or protect the host body against invading microorganisms. The ability of PMNS hence to potently and rapidly destroy the invading microbes is the major determinant of human health. When the PMNs are more in blood circulation, it denotes the septic status or the active infection present in the individual. PMNs are white blood cells that are capable of binding, ingesting, and eventually killing invasive microorganisms through a process called phagocytosis. The PMNs that are found specifically in the oral cavity are known as oral PMNs or oPMNS and have been studied by dental researchers exclusively and extensively in the field of periodontology. The aim of periodontal research over the last few decades has been to establish the role of oPMNS in maintaining oral immunity and defense.
What Is the Mechanism of Action of oPMNs?
oPMNS, just like PMNs, are considered to be professional phagocytes, which means that these cells can be functionally able to execute the phenomenon of phagocytosis. Several receptors have been found on the surfaces of oPMNS that initiate the phagocytic signaling pathway to eliminate infectious oral microbes, just as PMNs eliminate systemic infections. oPMNs can possess a range or a cocktail of antimicrobial agents such as alpha-defensins, cathepsins, elastase, lysozyme, proteinase-3, and lactoferrin.
All of which are located in distinct granule subsets of these cells. These granules or granule proteins such as the primary azurophilic granules, the secondary specific granules such as lactoferrin, or the tertiary granules such as gelatinase are a characteristic part of oPMNs. The delicate balance can be sustained between the oral microbiome and the innate immunity provided by the oPMNs in a healthy mouth or periodontium. When this dynamic equilibrium is lost, the migration of oPMNS to the site of oral inflammation can indicate the state of chronic disease or even progressive inflammation.
What Is the Role of oPMNs in Periodontal Infection?
Current research in the field of periodontology remains elusive regarding the exact entry or the mechanism of action of PMNS in the oral cavity. Over the last few decades, several research-based studies have been conducted and analytically measured the migration rate of PMNs into the oral cavity through the medium of the gingival crevicular fluid. In an active state of oral infection or inflammation, it is these oPMNS that are known to increase in the count or eventually migrate into the oral cavity at the site of inflammation or infection according to the latest dental research.
The oPMN migration rate is known to clinically correlate with the level of periodontal tissue inflammation. The presence or count of oPMN holds key importance in determining the presence of periodontal disease or inflammation in an individual. For instance, an individual who has periodontal Infection or inflammation in the oral cavity would have a higher count of oPMNS at the site compared to an individual who does not have any active oral or periodontal infection. Current research also shows that the oPMN numbers are rather indicative of the periodontal status of an individual. When the oPMNS are decreased, it would indicate tooth loss or tooth mobility subsequently due to the active infection leading to tooth loss. The presence of oPMNS can indicate the periodontal status of an individual as per dental research.
How Do the Cells Migrate Into the Gingival Crevicular Fluid?
The oPMNs are known to play an important role in controlling or sustaining the equilibrium among oral microbiome. In human saliva, the oPMNs are found in vast numbers where their integrity is preserved. Saliva which is an important barrier or line of defense in the mouth containing several immunoglobulins acts as a protectant of the oral cavity and ensures oral immunity. In saliva, the function of oPMNS remains completely in its active form. In the oral cavity, the periodontium is known to be the tooth-supporting organ acting as a protective cushion for the tooth. The periodontium also comprises several anatomical structures that give anchorage or support to the teeth. These structures basically comprise the gingiva, the periodontal ligament, the tooth root cementum, and the jaw or alveolar bone. The periodontal ligament is the soft connective tissue that is interposed in between the root of every tooth and connects the tooth to the inner wall of the alveolar socket.
Oral medicine and pathology researchers have histologically analyzed and studied the periodontal tissues over the last few decades. They concluded that the PMNs present in the oral cavity mainly leave the gingival blood supply that surrounds the teeth and passes through an extravascular connective tissue. These PMNS then enter the junctional epithelium as well as the pocket epithelium or the sulcular epithelium of the gingiva. Subsequently, these PMNs then get mixed into the fluids that are present in the gingival sulcus. This fluid known is as the gingival crevicular fluid. The gingival crevicular fluid (GCF) constantly flows into the oral cavity, through which the oPMNS are known to exert their mechanism of action.
Conclusion:
The oral mucosa is considered to be of fundamental import structure of the oral cavity and serves as the habitat of the neutrophils against any bacterial, viral, or fungal infections. PMNs are useful in dentistry and can measure the severity of oral inflammation or the oral inflammatory load. Oral polymorphonuclear cells can be found in patients suffering from inflamed periodontal tissues. The higher the oPMNs count, the greater the severity of the periodontal disease. It can hence prove to be a useful and reliable biomarker in detecting and quantifying periodontal diseases.
