BinaxNOW COVID-19 Antigen Rapid Self-Test at Home Kit | Walgreens

Nineteen or 19 may refer to:

• 19 (number)
• One of the years 19 BC, AD 19, 1919, 2019

In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response.

Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungi, and bacteria.

Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, antibodies are antigen-specific, meaning that an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react to bind more than one antigen. The reaction between an antigen and an antibody is called the antigen-antibody reaction.

Antigen can originate either from within the body ("self-protein" or "self antigens") or from the external environment ("non-self"). The immune system identifies and attacks "non-self" external antigens. Antibodies usually do not react with self-antigens due to negative selection of T cells in the thymus and B cells in the bone marrow. The diseases in which antibodies react with self antigens and damage the body's own cells are called autoimmune diseases.

Vaccines are examples of antigens in an immunogenic form, which are intentionally administered to a recipient to induce the memory function of the adaptive immune system towards antigens of the pathogen invading that recipient. The vaccine for seasonal influenza is a common example.

A home, or domicile, is a space used as a permanent or semi-permanent residence for one or more human occupants, and sometimes various companion animals. It is a fully- or semi-sheltered space and can have both interior and exterior aspects to it. Homes provide sheltered spaces, for instance rooms, where domestic activity can be performed such as sleeping, preparing food, eating and hygiene as well as providing spaces for work and leisure such as remote working, studying and playing.

Physical forms of homes can be static such as a house or an apartment, mobile such as a houseboat, trailer or yurt or digital such as virtual space. The aspect of 'home' can be considered across scales; from the micro scale showcasing the most intimate spaces of the individual dwelling and direct surrounding area to the macro scale of the geographic area such as town, village, city, country or planet.

The concept of 'home' has been researched and theorized across disciplines – topics ranging from the idea of home, the interior, the psyche, liminal space, contested space to gender and politics. The home as a concept expands beyond residence as contemporary lifestyles and technological advances redefine the way the global population lives and works. The concept and experience encompasses the likes of exile, yearning, belonging, homesickness and homelessness.

In philosophy, the self is an individual's own being, knowledge, and values, and the relationship between these attributes.

The first-person perspective distinguishes selfhood from personal identity. Whereas "identity" is (literally) sameness and may involve categorization and labeling, selfhood implies a first-person perspective and suggests potential uniqueness. Conversely, "person" is used as a third-person reference. Personal identity can be impaired in late-stage Alzheimer's disease and in other neurodegenerative diseases. Finally, the self is distinguishable from "others". Including the distinction between sameness and otherness, the self versus other is a research topic in contemporary philosophy and contemporary phenomenology (see also psychological phenomenology), psychology, psychiatry, neurology, and neuroscience.

Although subjective experience is central to selfhood, the privacy of this experience is only one of many problems in the philosophy of self and scientific study of consciousness.

Test(s), testing, or TEST may refer to:

• Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities

Walgreen Company is an American company that operates the second-largest pharmacy store chain in the United States, behind CVS Health. It specializes in filling prescriptions, health and wellness products, health information, and photo services. It was founded in Chicago in 1901, and is headquartered in the Chicago suburb of Deerfield, Illinois. On December 31, 2014, Walgreens and Switzerland-based Alliance Boots merged to form a new holding company, Walgreens Boots Alliance. Walgreens became a subsidiary of the new company, which retained its Deerfield headquarters and trades on the Nasdaq under the symbol WBA.

In 2021 the company was one of several pharmacy chains found by a federal jury to have substantially contributed to the opioid crisis.