Immunology

Immunology is the study of the immune system. Immune systems are parts of living things. They stop invasion and parasitism by other living things. The simplest form of it is the DNA restriction system in bacteria that prevents infection by bacteriophages.

Usually, Immunology means the study of immune systems in mammals. These systems are more complex than in other living things and also have more errors.

Types of immunity in mammals

There are two broad, artificial subdivisions of mammalian immune systems: the innate (or natural) and the acquired (or adaptive).

Innate immune response

The innate immune system is usually means all of the cells and systems that does not have to be exposed to a particular pathogen before they can work.

Innate immunity starts with the skin, which is an excellent barrier to infection.

Adaptive immune response

The adaptive immune system includes cells and systems that do require previous exposure to a pathogen. It explains the unique ability of the mammalian immune system to remember previous infections and mount a rapid and robust reaction to secondary infections. This immunological memory is due to the biology of T-cells and B-cells.

Other types of immunity

Herd immunity for instance is acquired by organisms living close together sharing minor infections often.

Vaccines boost the acquired immune system by offering weak forms of infection that the body can fight off. The system remembers how to do it again when a stronger infection happens. If the vaccine works, the body can then fight off a serious infection.

The distribution of vaccines and other immune system affecting cures can be considered another level of acquired immune system, one governed by access to vaccination and medicine in general. The intersection of this with the spread of disease (as studied in epidemiology) is part of the field of public health.

Errors and weaknesses

Errors of the immune system often cause more damage than what they are detecting and reacting to. In autoimmune diseases, the body attacks parts of itself because the system mistakes some parts of the body as 'foreign'. Some kinds of arthritis are caused this way.

Sometimes serious pathogens slip in because their surface is disguised as something the host cell walls can accept. That is how viruses work. Once inside a cell, their genetic material controls the cell. Infections like HIV get in this way, and then attack cells which are the basis of the immune system. Artificial means are often used to restore immune system function in an HIV-challenged body, and prevent the onset of AIDS. This is one of the most complex issues in immunology as it involves literally every level of that system. This research during the 1980s and 1990s radically changed the view of the human immune system and its functions and integration in the human body.

Integrated immune response

The natural or innate immune system of the human body is linked very deeply and directly to the nervous system and sensory system, a link first explored by studies on epilepsy. An epileptic attack is actually an immune system reaction triggered by a purely sensory or nervous input, like a strobe light. There are also studies of long term HIV survivors which suggest very strongly that psychology is a key healing factor and that it is quite possible to survive long term with very low immune system function if one avoids major psychological stress and stays quite calm and optimistic regardless of news. This might be because of the immune system's tendency to panic under conditions of high stress, to the detriment of the organism, sometimes attacking it from the inside.

Because of these issues, a view is evolving of a single system that responds cognitively to perception, physiologically with pain via nerves, and immunologically with the cells and chemical elements of the immune system that float in the blood, lymphatic system and tissues. The study of this system is psychoneuroimmunology. The immune system protects the body.