IMUNITY AND IMMUNISATION
immunity is meant the ability of a person to resist a
disease. When a disease organism gains
admittancetothe tissues of the body it will multiply and
either destroy local tissue or produce poisons which
will affect the whole body, or both. The ease with
which it can do this depends upon the person's immunity. Immunity may be natural or acquired. Natural Immunity is the resistance a person possesses golden colored items to wear in the formal occasion
to ward off an infectious disease with which he has
never before been in contact. This is partly hereditary and partly due to the state of
his health. Nature attempts to counteract antigens,
that is invading micro-organisms or other foreign
protein substances, by producing its own special
protective protein known as antibodies. To counteract the poisons (toxins) produced by
invading micro-organisms, the body also makes
antitoxins which are a special kind of antibody. For each toxin a separate specific antitoxin has to be
made. Our resistance today to tuberculosis is great. It no
longer is the scourge of Europe. Those of our ancestors
who had no natural immunity died early from the
disease, often before having children, and we are
mainly descended from those who had the ability to
survive. When Europeans first contacted the Pacific Islanders
they brought tuberculosis and measles (as well as other
diseases) to these people for the first time. The effect
was devastating. Our natural immunity may be enhanced by getting
sufficient sleep and by eating a well-balanced diet
including eggs, fish, meat, fruit and milk. Acquired Immunity. In some diseases we can reinforce
a person's natural immunity by vaccinating him so that
his body is stimulated to produce plenty of antitoxins
which will protect him against that particular disease.
This gives Active Immunity because the patient's
tissues actively cooperate in the process. A short-lived form is known as Passive Immunity. The
patient is given an injection of serum containing
antibodies or antitoxins when there is little or
insufficient time for his body to produce the antibodies
by the vaccination process. Active Immunisation. The patient's blood and tissue
cells are encouraged to produce antibodies against a
particular disease by the administration of killed or
attenuated (weakened) micro-organisms, usually in the
form of vaccines. As we all know, some diseases give lasting immunity.
One attack of smallpox, tetanus, or whooping-cough
will prevent the person from ever catching the disease
again. Other infections like the pneumonias, boils, in-fluenza,
and colds do not give lasting immunity. Therefore we
can only provide lasting active immunity against the
former diseases and not against the latter. In the case of whooping-cough, the patient may
become infected later by a related organism, Para-
pertussis, and appear to have a mild ‘second attack’ of
whooping-cough. Today we may actively immunise against certain
bacteria, viruses, and rickettsias. 1. Bacterial Diseases. Whooping-cough, tetanus,
diphtheria, cholera, typhoid, plague, and to some
extent tuberculosis (using B.C.G.). Immunisation against whooping-cough (pertussis),
tetanus, and diphtheria is usually (but not necessarily)
performed with a triple vaccine containing all three
disease antigens, and may be begun from the age of 3
months; a second and third injection are given after
two months then after six months; a booster dose of diphtheria and tetanus vaccine being given at school
entry age. 2. Virus Diseases. Smallpox, yellow fever, rabies,
poliomyelitis, and measles vaccines are available. Smallpox vaccination is commonly per-formed with
calf lymph. The cowpox virus in the lymph has been
weakened by giving it in repeated doses to the animal
until its tissues have produced plenty of protective
anti-bodies. The weakened virus antigens are located
in the serum which is then used for human vaccination. Primary vaccination for babies is not now compulsory
in Great Britain but at the parents' request it is
performed early in the second year of the child's life.
This confers immunity of a high degree for two to
three years and of a lesser degree for many years. In Great Britain revaccination of children may be done
just about school entry and should be repeated at
school leaving age-15 to 19. Revaccination should be undertaken when one is going
into an endemic area. This is performed in a manner
similar to that for infants and only a slight papule with
some itching results. Poliomyelitis vaccination is very easy to give. The oral
vaccine, prepared from live viruses (Types 1, 2, and 3)
attenuated or weakened by living for generations in a
tissue culture medium, is dropped on to a lump of
sugar and swallowed. The recommended course of
vaccination consists of three doses, each of three drops, given at the same visits as those for triple
vaccine. Measles vaccination need not be given until a baby is
about a year old since it is immune to measles for six
months or more owing to the presence of maternal
antibodies in its serum. Rubella (German Measles). The live rubella virus vaccine
is offered routinely to all girls between their eleventh
and fourteenth birth-days. Immunity is of long
duration. 3. Rickettsial Diseases. One may be immunised against
typhus if one is travelling through or living in an
endemic area. Passive Immunisation. This is performed by injecting
serum which has been prepared, usually in horses, by
actively immunising an animal against a specific
disease. Sometimes one may use a serum from a convalescent
patient. The serum contains anti-bodies or antitoxins
against a particular organism or toxin. This form of
immunisation is sometimes of great use in an
epidemic. If a pregnant woman (6 to 12 weeks pregnant) who
has not had German measles has contracted, or is in
contact with cases of German measles, then it is a wise
precaution to passively immunise her. This will prevent
her getting the disease and so affecting the faetus.
Another instance of its use is against poliomyelitis. Queen Elizabeth II, when touring Australia, was forced
to travel during an epidemic of poliomyelitis and so
she was passively immunised with human gamma
globulin. When a person is wounded and there is any possibility
of dirt in the wound, or the doctor considers it to be
tetanus-prone, then an injection of A.T.S. (antitetanus
serum) is given. This is to counteract the toxin
produced by Clostridium tetani. It must be repeated that passive immunisation is
evanescent and its maximum duration of action is five
to six weeks.