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What Is The Immune System And How Does It Relate To Allergies?

Immune System

What Is The Immune System And How Does It Relate To Allergies?

The immune system exists to protect us against harmful “foreign” invaders and internal enemies.  It takes a multipronged approach to defense and is comprised of a number of cells, tissues, and organs.

The most common external threats that the immune system defends us against are microbial organisms such as viruses, bacteria, fungi, and/or parasites.  Specialized cells in that make up part of the immune system perform internal surveillance to detect and destroy harmful things such as cancers at early stages.  Survival is not possible without an adequately functioning immune system.

There are two main parts in this very complex system:

  1. Innate Immunity:  This evolutionally older system is the usual first line of defense against harmful agents.  The cells that are functional in this system are general killer cells and scavenger cells such as neutrophils, eosinophils, mast cells, and macrophages.  Neutrophils, eosinophils, and mast cells are types of white blood cells.  Macrophages are derived from monocytes (i.e., another type of white blood cell) and are specialized cells of the immune system that recognize, engulf, and destroy microbes and other “invaders.”  All of these cells provide non-specific protection mainly against bacterial infections.
  2. Adaptive Immunity:  This is a learned and specific defense system mediated chiefly by lymphocytes (i.e., a type of white blood cell).  These cells form antibodies, which “memorize” previous contacts with the pathogens (i.e., bacteria, viruses) and can recall and mount a rapid response on subsequent exposures to the same and similar microbes.

These two systems complement each other and work in harmony to maximize the defensive capabilities.


  1. Skin:  Immune cells are present in specific layers of the skin and they produce and secrete proteins which can neutralize many microorganisms.
  2. Bone Marrow:   The birth place for “stem cells” which have the potential to differentiate into many specialized cell types involved in both innate and adaptive immune systems.
  3. Bloodstream:   Immune cells constantly circulate in the blood, patrolling for harmful substances.
  4. Thymus:   A small gland in the upper chest where lymphocytes mature.
  5. Lymphatic system:  Immune cells are also part of a fluid called lymph, which transports microbes and their products from the area of exposure via lymphatic vessels to regional lymph nodes, where they are processed.
  6. Spleen:  Immune cells are enriched in specific areas of the spleen and blood borne pathogens are inactivated.
  7. Mucosal surfaces:  Mucus membranes are the first point of entry by many viruses and bacteria.  Immune cells are strategically located in the mucosal areas of the respiratory and gastrointestinal tracts.

There are primarily three ways in which the immune system can malfunction:

  1. Immunodeficiency:  When enough immune cells are not produced by the marrow and/or when they are functionally inadequate, the host is susceptible to frequent and severe infections by viruses, bacteria, and unusual and opportunistic fungi.  These conditions can either be “primary”, where the condition is present from birth or early childhood (some varieties are incompatible with life) or “secondary”, where the condition begins later in life.  Medications such as corticosteroids are immune suppressants and cause a deficiency of the immune system.  HIV/AIDS is an example of a virus infection that causes a secondary immune deficiency.
  2. Autoimmunity:  A fundamental ability of immune cells is to distinguish between self and non-self.  However this capacity is compromised in certain situations and the immune system turns against our own tissues and organs and may cause long-lasting damage.  Systemic lupus erythematosus is a common example of an autoimmune disorder.  There are many other connective tissue and endocrine diseases that are thought to have an autoimmune component.
  3. Allergic disorders:  When the immune system mistakes innocuous substances as potentially harmful and mounts a defensive attack against them, “allergy” results.  The most common substances that the immune system reacts to are dust mites, molds, and pollens (e.g., trees, grasses, weeds).  This mistaken immune response against these usually harmless environmental agents usually results in disorders affecting the eyes, nose, throat, and lungs.  The immune system also occasionally mistakes certain foods and helpful drugs such as penicillin as potentially harmful and attacks them.  The result may manifest itself as skin rashes, gastrointestinal symptoms, and rarely severe life-threatening reactions called anaphylaxis.

DIAGNOSIS:  The function of the immune system can be evaluated by measuring the numbers and functional abilities of various immune cells obtained from blood sampling and occasionally bone marrow.  Sometimes the ability of the immune system to respond to immunizations in terms of manufacturing specific IgG antibodies is helpful in establishing a diagnosis.

Disorders caused by autoimmunity are usually detected by identifying specific “auto-antibodies” in the bloodstream.  Allergic disorders are diagnosed by measuring specific IgE antibodies to the common “antigens”, which are the triggers of allergic reactions, either by skin tests and/or blood tests.  Sometimes either inhalation or ingestion “challenges” are required to confirm the diagnosis.

TREATMENT:  The frequency and severity of infections in immunodeficiency diseases can be minimized either by prophylactic antibiotic therapy on a long term basis or by replacement of IgG immunoglobulins by regular subcutaneous injections or intravenous infusions.

Immunosuppressive drugs are helpful in controlling organ and tissue damage in selected autoimmune disorders in addition to symptomatic treatment.  Replacement of hormones suppressed by organ damage (e.g., thyroid hormone) may be needed in autoimmune diseases affecting certain organ systems.

Allergic disorders are treated by medications such as antihistamines to block the chemical mediators of symptoms, injectable biological medications, and topical and inhaled corticosteroids to control allergic inflammation.  Allergy immunotherapy (i.e., allergy shots, allergy desensitization, allergy hyposensitization) provides long term relief from symptoms by increasing the tolerance to the offending allergens by modulating the immune system.

The board certified allergists at Black & Kletz Allergy have the expertise in the practice of immunology and allergy to evaluate and treat immunological problems in both children and adults.  We have offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VAand have on-site parking at each location.  Our Washington, DC and McLean, VA offices are Metro accessible and there is a free shuttle that runs between our McLean, VA office and the Spring Hill metro station on the silver line.  If you know or think that your immune system is suppressed, please call us or click Request an Appointment to schedule an appointment. If you choose to request an appointment online on our website, we will respond within 24 hours by the next business day.  The allergy specialists at Black & Kletz Allergy are eager to help you as we have been doing in the Washington, DC metro area for more than a half century.