Biology of Disease

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DISORDERS OF THE

IMMUNE SYSTEM

5.1 Introduction

A fully functioning immune system is essential for maintaining health
(Chapter 4) but, like all body systems, the immune system itself is subject to
many clinical disorders. Immunological disease can occur for one of three
reasons. Firstly, immunodeficiency diseases occur in individuals whose
immune systems are inadequate, perhaps due to the absence or malfunction
of essential components, making them susceptible to infectious disease and
even to certain types of cancer. Secondly, autoimmune diseases can occur as
a result of the immune system mounting an immune response against ‘self’
components. Finally, immunological hypersensitivity occurs when immune
responses, often mounted against seemingly innocuous immunogens, result
in tissue damage. Indeed, immunological hypersensitivities are among the
commonest of immunological disorders. This chapter will examine the variety,
etiologies, diagnoses and treatments of these three groups of immunological
disorders.

OBJECTIVES

After studying this chapter you should be able to:

N describe the features and explain the clinical consequences of

immunodeficiency diseases;

N describe the features and explain the clinical consequences of autoimmune

diseases;

N describe the features and explain the clinical consequences of immunological

hypersensitivity;

N outline the ways in which immunological disorders are investigated and

treated.