Adaptive immune system (adaptive immunity) – The body’s second line of defense against pathogens. If the innate immune system is unable to destroy a pathogen, the adaptive immune system steps in with a targeted response. This type of immunity learns how to fight the intruder, but also remembers it, for a faster response the next time it is encountered.

Allele – Any one of the potentially many alternative (variant) forms of a gene.

Bitter taste agonists – A substance meant to activate bitter taste receptors.

Bitter taste receptors (BTRs) – Components of some taste buds that are specifically tuned to detect bitter tastes.

Bitter taste sensitivity – The spectrum of bitter taste intensity levels experienced when exposed to bitter taste agonists.

COVID-19 – Coronavirus disease 2019.

Genotype – An inherited collection of genetic material. This term can also refer to a specific set of genes. Genotypes can only be determined through genetic testing known as genotyping.

Haplotypes – A collection of alleles on a chromosome that are often inherited together from a single parent.

ImmuneX – The innate immunity conferred by T2R38 BTRs

ImmuneY – Unmodifiable factors that may affect your immunity. Examples include your age, sex, race, and family history of certain diseases like diabetes or cystic fibrosis.

ImmuneZ – Modifiable factors that may influence your immunity. Examples include nutrition, weight, and sleep, among others.

Innate immune system (innate immunity) – The body’s first line of defense against pathogens. The innate immune system is comprised of various physical, chemical, and cellular defenses that react immediately when a foreign particle is encountered.

Pathogen – Any organism or substance that causes disease. Examples include viruses, bacteria, or fungi.

PAV/AVI – The two most common haplotypes of the T2R38 gene. PAV is the functional variant, whereas AVI is the non-functional variant.

Phenotype – Observable or measurable traits, such as hair color or eye color. Both genotype and environmental factors may influence phenotype. Often, more than one gene influences a specific trait.

Phenotypic expression – The measurable/observable traits that indicate phenotype. While a genetic test is required to determine genotype, no genetic material is required to determine phenotype.

Phenylthiocarbamide (PTC) – As well as 6-n-Propylthiouracil (PTU), a special chemical that mimics the bitter taste of toxic substances. It is regularly used in bitter taste sensitivity testing, as only very low concentrations are needed to trigger an intense reaction in people with high levels of bitter taste sensitivity.

SARS-CoV-2 – Severe Acute Respiratory Syndrome Coronavirus 2. The virus that causes COVID-19.

Sinonasal innate immunity – The components of the innate immune system found in the sinus and nasal cavity.

T2R38 bitter taste receptors (BTRs) – A specific set of bitter taste receptors coded by the T2R38 gene. These BTRs have been the focus of much scientific research which suggests they may be linked to sinonasal innate immunity.

T2R38 gene – The specific set of genetic material responsible for producing T2R38 BTRs.