AntigenIn 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.
ArabsThe Arabs (عَرَب, DIN 31635: DIN, Arabic pronunciation: ˈʕa.rab), also known as Arab people (الشَّعْبَ الْعَرَبِيُّ), are an ethnic group mainly inhabiting the Arab world in West Asia and North Africa, which formally denotes the "Arab homeland". Moreover, a significant Arab diaspora is present in various parts of the world. According to the Abrahamic tradition, Arabs are descendants of Abraham through his son Ishmael. Islamic sources further propose that Abraham brought Hagar and Ishmael to Mecca.
