A substance or signal that initiates a developmental process in embryology or gene expression in molecular biology.

Also known as noble gases; elements like helium and neon that are chemically nonreactive.

The invasion and multiplication of pathogenic microorganisms in a host organism.

A disease caused by the presence of pathogenic microorganisms, such as bacteria, viruses, or fungi.

An ovary positioned below the point of attachment of other floral parts.

Unable to produce offspring or incapable of reproduction.

A multiprotein complex in immune cells that activates inflammatory responses by promoting the secretion of cytokines.

A class of proteins that function as antibodies in the immune system.

Antibodies classified into five major types (IgA, IgD, IgE, IgG, IgM) based on their structure and immune function.

A scientist or medical specialist who studies or treats disorders of the immune system.