Microbiology and Immunology

Burnet, Frank Macfarlane WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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buffer system compensates for such additions and maintains

the pH within the required range.

This buffering system is intimately tied to respiration,

and an exceptional feature of pH control by this system is the

role of ordinary breathing in maintaining the pH. Carbon diox-

ide is a normal product of metabolism. It is transported to the

lungs, where it is eliminated from the body with every exhala-

tion. However, carbon dioxide in blood is converted to car-

bonic acid, which dissociates to produce the hydrogen

carbonate ion and the hydronium ion. If a chemical reaction or

the ingestion of an acidic material increases the hydronium ion

concentration in the blood, bicarbonate ion reacts with the

added hydronium ion and is transformed into carbonic acid.

As a result the concentration of dissolved carbon dioxide in

the blood increases. Respiration increases, and more carbon

dioxide is expelled from the lungs. Conversely, if a base is

ingested, the hydronium ion reacts with it, causing a decrease

in the concentration of hydronium ion. More carbonic acid

dissociates to restore the hydronium ion consumed by the

base. This requires more carbon dioxide to be dissolved in the

blood, so respiration is decreased and more gas is retained.

To act as a buffer, a solution must maintain a nearly con-

stant pH when either acid or base is added. Two considerations

must be made when a buffer is prepared: (1) Which pH is

desired to maintain? The desired pH defines the range of the

buffer. (2) How much acid or base does the solution need to

consume without a significant change in pH? This defines the

capacity of the buffer. The desired pH also determines the

compounds used in making up the buffer. The quantity of acid

or base the buffer must be able to consume determines the

concentrations of the components that must be used, and

which allows biological reactions to take place consistently.

See alsoBiochemical analysis techniques; Laboratory tech-

niques in microbiology

BURNET, FRANKMACFARLANE

(1899-1985)Burnet, Frank Macfarlane

Australian immunologist and virologist

While working at the University of Melbourne’s Walter and

Eliza Hall Institute for Medical Research in the 1920s, Frank

Macfarlane Burnet became interested in the study of viruses

and bacteriophage(viruses that attack bacteria). That interest

eventually led to two major and related accomplishments. The

first of these was the development of a method for cultivating

viruses in chicken embryos, an important technological step

forward in the science of virology. The second accomplish-

ment was the development of a theory that explains how an

organism’s body is able to distinguish between its own cells

and those of another organism. For this research, Burnet was

awarded a share of the 1960 Nobel Prize for physiology or

medicine (with Peter Brian Medawar).

Burnet was born in Traralgon, Victoria, Australia. His

father was Frank Burnet, manager of the local bank in

Traralgon, and his mother was the former Hadassah Pollock

MacKay. As a child, Burnet developed an interest in nature,

particularly in birds, butterflies, and beetles. He carried over

that interest when he entered Geelong College in Geelong,

Victoria, where he majored in biology and medicine.

In 1917, Burnet continued his education at Ormond

College of the University of Melbourne, from which he

received his bachelor of science degree in 1922 and then, a

year later, his M.D. degree. Burnet then took concurrent posi-

tions as resident pathologist at the Royal Melbourne Hospital

and as researcher at the University of Melbourne’s Hall

Institute for Medical Research. In 1926, Burnet received a

Beit fellowship that permitted him to spend a year in residence

at the Lister Institute of Preventive Medicine in London. The

work on viruses and bacteriophage that he carried out at Lister

also earned him a Ph.D. from the University of London in

1927. At the conclusion of his studies in England in 1928,
      Burnet returned to Australia, where he became assistant direc-
      tor of the Hall Institute. He maintained his association with the
      institute for the next thirty-seven years, becoming director
      there in 1944. In the same year, he was appointed professor of
      experimental medicine at the University of Melbourne.
      Burnet’s early research covered a somewhat diverse
      variety of topics in virology. For example, he worked on the
      classification of viruses and bacteriophage, on the occurrence
      of psittacosis in Australian parrots, and on the epidemiologyof
      herpesand poliomyelitis. His first major contribution to virol-
      ogy came, however, during his year as a Rockefeller fellow at
      London’s National Institute for Medical Research from 1932
      to 1933. There he developed a method for cultivating viruses
      in chicken embryos. The Burnet technique was an important
      breakthrough for virologists since viruses had been notori-
      ously difficult to cultureand maintain in the laboratory.
      Over time, Burnet’s work on viruses and bacteriophage
      led him to a different, but related, field of research, the verte-
      brate immune system. The fundamental question he attacked
      is one that had troubled biologists for years: how an organ-
      ism’s body can tell the difference between “self” and “not-
      self.” An organism’s immune system is a crucial part of its
      internal hardware. It provides a mechanism for fighting off
      invasions by potentially harmful—and sometimes fatal—for-
      eign organisms (antigens) such as bacteria, viruses, and fungi.
      The immune system is so efficient that it even recognizes and
      fights back against harmless invaders such as pollen and dust,
      resulting in allergic reactions.
      Burnet was attracted to two aspects of the phenomenon
      of immunity. First, he wondered how an organism’s body dis-
      tinguishes between foreign invaders and components of its
      own body, the “self” versus “not-self” problem. That distinc-
      tion is obviously critical, since if the body fails to recognize
      that difference, it may begin to attack its own cells and actu-
      ally destroy itself. This phenomenon does, in fact, occur in
      some cases of autoimmune disorders.
      The second question on which Burnet worked was how
      the immune system develops. The question is complicated by
      the fact that a healthy immune system is normally able to rec-
      ognize and respond to an apparently endless variety of anti-
      gens, producing a specific chemical (antibody) to combat each
      antigenit encounters. According to one theory, these antibod-

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