Salivary IgG

Intended Use

The Salimetrics® Salivary Human Total IgG ELISA Kit is an enzyme-linked immunoassay specifically designed and validated for the quantitative measurement of human total IgG in oral fluid. It is not intended for diagnostic use. This assay kit was optimized for human salivary research and has not been validated for other human sample types, such as serum or plasma or samples from other species.

Introduction

High titers of pathogen specific IgG are a measure of protective immunity against pathogens and are generated by an immune response to either a prior infection event or immunization (2). Most IgG in saliva originates from the serum entering into saliva passively through the gingival crevicular epithelium, however some is produced locally in the salivary glands or gingiva (3). Importantly, the reactivity of salivary IgG mirrors that of serum IgG, so oral fluid is an attractive alternative sample to blood for serological studies where antibody levels indicate an individual’s immune status to a pathogen of interest (4, 5). As an alternative to blood, oral fluid enables advantages like home collection or when sampling populations where blood draws are a challenge, for instance in small children or the elderly (6).

One important application for the measurement of total IgG in oral fluid is to qualify samples as having sufficient antibody levels to enable valid serological studies (6). In this case, since oral fluid may vary in the amount of antibody present at the time of sampling, to definitively determine if an individual shows negative reactivity, the sample must be tested for total IgG levels to assure there is adequate total antibody present in the test. Cutoff levels may be established to determine if a sample has adequate IgG as well as to help interpret the relative degree of positivity in samples that show reactivity.

In addition, it has been recently reported that levels of total IgG in oral fluids is highly correlated with proinflammatory cytokine levels, suggesting that, in certain applications, total salivary IgG could be used as a surrogate, and inexpensive marker, to index oral inflammation (7). In this case, total IgG in saliva may be a useful covariate in statistical analyses to control for the confounding effects of poor oral health. This might be very important if the study participants are at high risk for oral health problems.

SALIVARY HUMAN TOTAL IgG ASSAY PRINCIPLE

This is an indirect sandwich ELISA kit. A “sandwich” is formed when the pre-coated capture Anti-Human IgG antibody present on the plate binds IgG in standards & samples, which is then bound by the Anti-Human IgG detection antibody linked to horseradish peroxidase. After each incubation, unbound components are washed away. Bound Anti-Human IgG Antibody Enzyme Conjugate is then added and the levels measured by the reaction of the horseradish peroxidase (HRP) enzyme to the substrate tetramethylbenzidine (TMB). This reaction produces a blue color. A yellow color is formed after stopping the reaction with an acidic solution. The optical density is read on a standard plate reader at 450 nm. The total amount of IgG Antibody Enzyme Conjugate detected is directly proportional to the amount of Total Human IgG present in the sample.