Immunology is defined as the study of the molecules, cells, organs, and systems responsible for the recognition and disposal of foreign material. Immunology began as a branch of microbiology. The study of infectious disease and the body’s response to them has a major role for the development of immunology. Moreover, the concept of germ theory of disease has contributed to the field of immunology.
Immunity can be defined as the way in which the body can protect itself from invasion by pathogenic microorganism and provide a defense against their harmful effect. Immunity is classified in to two major groups • Nonspecific immunity • Specific immunity
The specific immune response, also called acquired or adaptive immunity, is a defense system that protects the body against pathogenic microorganisms and other type of disease such as cancer. It allows the body to recognize, remember, and respond to a specific stimulus, an antigen.
Specific immunity can result in the elimination of microorganisms and in the recovery from disease, and it frequently leaves the host with specific immunologic memory. This condition of memory or recall, acquired resistance, allows the host to respond more effectively if reinfection with the same microorganism occurs.
As a consequence of such acquired immunity, we usually suffer from many diseases only once, for example measles. Specific immunity can be active or passive, and each of these types can in turn be naturally or artificially acquired.
It is an immunity in which antibodies produced elsewhere are given to the individual. They are divided into two:
I. Naturally acquired passive immunity: refers to antibodies transferred from mother to fetus across the placenta and to the newborn in colostrums and breast milk during the first few months of life.
ii. Artificially acquired passive immunity: is introduction of antibodies that are formed by an animal or a human to an individual to prevent or treat infection.
Active immunity It is a product of the individual’s own immune system in response to a foreign antigen.
I. Naturally acquired active immunity: is immunity that comes from infections encountered in daily life.
ii. Artificially acquired active immunity: It is stimulated by initial exposure to specific foreign macromolecules through the use of vaccines to artificially establish a state of immunity.
Factors Associated With Immunologic Disease
Many factors appear to be responsible for differences in the immunity of individual’s age; nutrition and genetic factor are some of them.
Although non-specific and specific body defense are present in the unborn and newborn infants, many of these defenses are not completely developed in this group. Therefore young children are at greater risk for disease. In older adults certain natural barriers to infection break don such as changes in the skin and in the lung weakening of specialized defenses against foreign invasion including the cough reflex. In general, the ability to respond immunologically to disease is age related.
Nutrition The importance of good nutrition to good health has always been emphasized. Good nutrition is known to be important to growth and development. The consequences of diet in many aspects of the immune response have been documented in multiple disorders. Every constituent of the body defense appears to influence by nutritional intake. Therefore a healthy diet is important for maximum functioning of the immune system
The possession of certain genes is linked to immune disorders these include genes that lead to a deficiency in the production of neutrophilis and complement. Sickle cell disease predisposes to pneumococcal bacteraemia or Haemophilus influenza and E. coli infection.