Page 1553 - Veterinary Immunology, 10th Edition

VetBooks.ir Neutrophils Polymorphonuclear neutrophil granulocytes.

Noncovalent bonds Chemical bonds, such as hydrogen or
hydrophobic bonds, that reversibly link peptide chains. They

play a key role in the binding of antigen with antibodies or with
T cell antigen receptors.

Nucleocapsid The key structural component of a virus consisting
of the viral nucleic acid and its protective capsid coat.

Nude mice A mutant strain of mice that have no thymus and are
hairless.

O

O antigens Somatic antigens of Gram-negative bacteria.

Obligate intracellular parasite An organism that is absolutely
required to grow inside cells. Viruses are excellent examples.

Oncofetal antigens Antigens found on fetal and tumor cells.

Oncogene A gene whose protein product plays a key role in cell

division. As a result, its uncontrolled production leads to
excessive cell growth and tumor formation. Oncogenes may be
found in normal cells, as well as in cancer-causing viruses.

Oncogenic virus A virus that causes cancer.

Ontogeny The embryonic development of an organ or animal.

Opportunistic pathogen An organism that, although unable to

cause disease in a healthy individual, may invade and cause
disease in an individual whose immunological defenses are
impaired.

Opsonin A molecule that facilitates phagocytosis by coating
foreign particles.

Optimal proportions When antigen and antibody combine, this is
the ratio of reactants that generates the largest immune

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