The immune system has evolved to protect the host from
pathogens while minimising damage to self tissue.
Despite the ancient observation that recovery from
some diseases results in protection against that condition,
the existence of the immune system as a functional
entity was not recognised until the end of the 19th
century. More recently, it has become clear that the
immune system not only protects against infection, but
also influences healing and governs the responses that
can lead to autoimmune diseases. Dysfunction or deficiency
of the immune response leads to a wide variety
of diseases, involving every organ system in the body.
The aim of this chapter is to provide a general understanding
of immunology and how it contributes to
human disease. A review of the key components of the
immune response is followed by five sections that illustrate
the clinical presentation of the most common forms
of immune dysfunction. Clinical immunologists are
usually involved in managing patients with allergy and
immune deficiency.