Vincent St Aubyn Crump -
Article written: November 2002
The human immune system is a
complex defence system, consisting of cells and proteins that act
together; to fight infections caused by bacteria, viruses, and
parasites. We are constantly exposed to infectious agents, and
everyone gets an infection once in a while. However, some people get
recurrent infections. There are several reasons for these individuals to
have an increased susceptibility to infections.
In assessing the child
with recurrent infections one need's to remember the rarity of true
immunodefeciency and the high prevalence of allergy (atopy), attendance to day care (with high level exposure to
bugs), and anatomic variations as predisposing factors for infections.
The major function of the
immune system is to recognise foreign substances and react
to them. An immune system that is functioning adequately should defend
the body from infectious organisms (bacteria, viruses, fungi, and
parasites) and protect the body from development of cancers. The major
organs of the immune system include the bone marrow, liver, thymus,
tonsils, lymph nodes, the spleen, and blood. These organs manufacture,
process and store the major components of the immune system, which
• T- Lymphocytes or
T-cells - White blood cells important in regulating the immune
system and helping fighting viral infections.
• B- Lymphocytes or B-cells - Cells that make specific proteins
called antibodies to protect from bacteria that cause ear
infections, sinusitis and pneumonia, etc. The chemical name for antibody
proteins is immunoglobulins or gammaglobulins. There are four major
classes of antibodies or immunoglobulins:
1. Immunoglobulin G (IgG)
2. Immunoglobulin A (IgA)
3. Immunoglobulin M (IgM)
4. Immunoglobulin E (IgE)
Each immunoglobulin class
has special chemical characteristics that provide it with specific
advantages. For example, antibodies in the IgG fraction are formed in
large quantities, last for over a month and travel from the blood stream
to the tissues easily. The IgG antibodies are the only immunoglobulins
that cross the placenta and pass immunity from the mother to the
newborn. Because our immune system can't make the most important
antibody, IgG, in sufficient quantity until about six months of age, IgG
antibodies passed on by a mother before birth, protects the baby. If the
baby's own immune system does not "turn on" at the right time, the child
may get recurrent infections. This is called "Transient
hypogammaglobulinemia (low immunoglobulin) of infancy", transient
because the child will outgrow it by the age of 2 or 3 years, as the
immune system matures.
IgA antibodies are
produced near mucous membranes and find their way into secretions such
as tears, saliva, and mucus, where they protect against infection in the
respiratory tract and intestines.
IgM antibodies are the
first antibodies to be formed in response to infection. Therefore, they
are important in the early days of an infection.
IgE antibodies are
responsible for allergic reactions and parasitic infections.
• Phagocytes -
Cells that ingest foreign bodies and bacteria to kill them.
• Complement - Proteins that may kill bacteria that may cause
Immunodeficiency occurs when the abnormality to the immune system
develops from an inborn defect in the cells. It is a disorder in immune
function that is not a result of infection (eg. AIDS) or extrinsic
manipulation. The cells that are affected include T-cells, B-cells,
phagocytic cells, or the complement system. Most primary immune
deficiencies are inherited diseases. The disease is not always
evident at birth. There are about 95 known primary immunedeficiency
diseases. Some examples of Primary Immunodeficiencies include:
• Selective IgA
deficiency - relatively common, about 1/333 - 1/1000 in USA
• Severe common immunodefeciency (SCID)
• Common variable immunodefeciency (CVID)
• X-linked Agammaglobulinemia (XLA)
While primary immune
deficiencies are uncommon it is essential they be diagnosed promptly to
prevent damage to organs such as the lungs and ears, and also to prevent
life threatening infections. A careful history, physical examination,
and sometimes a simple blood test are often all that is required to rule
out an underlying immune deficiency.
deficiencies occur when damage is caused by an environmental factor.
Radiation, chemotherapy, burns, and infections contribute to the many
causes of secondary immune deficiencies. Acquired Immune Deficiency is a
secondary immune deficiency caused by the Human Immunedeficiency Virus
(HIV). In Leukemia, Lymphomas, and metastatic cancer, abnormal cancerous
cells crowd out normal stem cells of the bone marrow. These abnormal
cells reduce the number of B cells and lead to hypogammaglobulinemia or
secondary immune deficiency.
Warning signs of Primary Immunodeficiency
(Compiled by the Medical
Advisory Board of Jeffery Modell Foundation)
• 8 or more ear
infections within 1 year
• 2 or more serious sinus infections within 1 year
• 2 or more months on antibiotics with little effect
• 2 or more pneumonia within 1 year
• Failure of an infant to gain weight or grow normally
• Frequent deep skin or organ abscesses
• Need for intravenous antibiotics to clear infections
• Persistent thrush in the mouth or elsewhere on the skin after 12
months of age
• 2 or more deep seeded infections such as meningitis, osteomyelitis,
cellulitis, or sepsis.
• Family history of Primary Immunodeficiency
Infections caused by increased exposure to bugs seen in normal
A study in the USA in the
80's showed that recurring middle-ear infections among preschoolers rose
sharply between 1981 and 1988, in part because more children were in day
care centres than before.
The most common
infections are viral respiratory tract infections (the common cold). The
average young child may get up to 12 colds a year. Typically, cold
symptoms last 5-10 days. These frequent colds are usually not a cause
for concern, as colds are a result of the close contact of young
children with a relatively immature immune system.
and recurrent infections
In people with allergies,
there is an over-reaction and loss of control, where the immune system
launches attack against a perfectly harmless substance, such as grass
pollen, cat dander or peanut or penicillin. The harmful end results of
these attacks are called immediate hypersensitivity or allergy.
The first line of defence
against infection is located where the body has contact with the rest of
the world. In atopic eczema, where the skin barrier is often broken from
scratching, it is easy for organisms to enter the skin and cause
infection. Similarly, inflammation (irritation, swelling and injury) to
the mucous membranes lining the nose, sinuses, and lungs provide a
fertile ground for secondary infections. In patients who have year-round
allergies to house dust mites, pollen and moulds, there will be some
injury to the mucus membranes, which increases their susceptibility to
Nasal blockage due to
allergic rhinitis is also thought to lead to secretions and eustachian
tube blockages that promote ear infections.
Many people confuse
persistent (perennial) allergic rhinitis due to house dust mites or cat
allergy with a prolonged cold or sinus infection, since the symptoms of
nasal stuffiness, nasal itch, and runny nose are common to both. It is
therefore important for all patients with "prolonged cold symptoms or
sinusitis" to have a skin prick test for inhalant allergens.
There is also good
evidence to suggest that atopic (allergic) individuals have an inherited
defective (abnormal) B and T cell functioning, which contributes to
their increased risk (and prolongation) of infections.
Structural (Anatomical) changes causing recurrent Infections
Structural changes in the
sinuses or Eustachian tubes (connecting tubes in each ear) are a cause
of repeated infections in childhood. The term "structural changes"
refers to differences in the bony parts of the skull, the sinuses, and
ears. These differences are often inherited. These differences in body
structure makes it easier for that person to get infections because the
normal drainage of the (Eustachian tubes (in the ear) or sinuses (in the
nose) is blocked. Another common anatomical variation (abnormality) is a
deviated nasal septum (the cartilage, usually midline, which separates
right and left nostrils. This predisposes to improper drainage of the
sinuses on the narrower side, especially when there is also nasal
blockage from any cause, but commonly from allergic rhinitis.
• Recurrent infections in
early childhood are usually normal, and relate to a relatively immature
• Allergies can present as recurrent infections, or be a predisposing
factor for recurrent infections, therefore all kids with recurrent
infections should be considered for skin prick testing.
• Primary Immunodeficiency is rare but should be considered in anyone
with recurrent infections, especially if the infections are severe,
difficult to treat or caused by unusual bugs.
• While primary immune deficiencies are uncommon it is essential they be
diagnosed promptly to prevent organ damage and life-threatening
• A careful history, physical examination, and sometimes a simple blood
test are often all that is required to rule out an underlying immune