Classical immunology deals with the fields of epidemiology and medicine. Immunology alone is the study of response of an organism to antigenic challenge and its recognition of what is self and what is not. It deals with the defence mechanisms including all physical, chemical and biological properties of the organism that help it to combat its susceptibility to foreign organisms, material, etc. Classical immunology deals with the relationship between the body systems, pathogens, and immunity.

Ancient references to immunology

Reference to immunology and immunity has been seen in ancient literature as well. The earliest written mention of immunity can be traced back to the plague of Athens in 430 BCE. It was Thucydides who noted that people who had recovered from a previous bout of the infectious disease could nurse the sick without contracting the illness a second time. It was in the 19th and 20th centuries that the concepts of immunology finally were developed as a scientific theory and were understood in greater detail.

Studying the immune system

The immune system is studied as per its molecular and cellular components. Their function and interaction form the core of study of immunology as we know today. The immune system is divided into those which are static, or innate to the organism, and those which are responsive, or adaptive to a potential pathogen or foreign substance.

To maintain the integrity of our organism, it is essential to distinguish between self and non-self. Early in evolution, simple multicellular organisms developed a defence system activated by sensing typical molecules and chemical structures associated with pathogens. This system is evolved to its present day immunology. This innate, prefabricated, one-size-fits-all immune system is immediately available. It stops the pathogens and keeps an infection in check for a few days. After the first defence is overwhelmed the adaptive immune system kicks in.

The humoral response is a response of antibodies produced by the body to antigens. Antibodies are specific proteins released from a certain class of immune cells (B lymphocytes). Antigens are proteins or chemicals or even living organisms that elicit generations of antibodies, hence they are called Antibody Generators. Immunology is the study of these two biological entities.

Once exposed to antigens the body mounts a cellular response. This can kill infected cells in its own right and also controls the level of antibody response. The whole system is a highly balanced one and there are disorders of both under-active as well as over-active immune system. Both activities are highly interdependent.

In this century immunology has spread its frontiers with much research being performed in the more specialized niches of immunology. This includes the immunological function of cells, organs and systems not normally associated with the immune system along with studies of classical models of immunity.