Beyond the Basics: Immune Response

CEU Review Form Beyond the Basics: Immune Response (PDF) Valid until August 4, 2008

     The human immune response is arguably among the most difficult processes for an EMS provider to understand. The immune system provides front-line defense to any potentially inflammatory process, with the goal of destroying or inactivating pathogens, abnormal cells and foreign substances. The system includes the thymus, spleen, lymph nodes, lymphoid tissues (as in the GI tract and bone marrow), macrophages, lymphocytes, including B and T cells, and antibodies, among others. On the surface, the skin and stomach acid serve as physical barriers to invasion. This article will primarily concentrate on the immune response to allergies, but will discuss some other immune disorders to illustrate the role of the immune system in common disease processes.

PHYSIOLOGY OF THE IMMUNE SYSTEM
     The immune system is critically important to human survival because of continuous exposure to pathogens, toxins and other foreign substances. As time progresses, the immune system continually matures to meet environmental changes. Without immune-mediated responses, the body would not be capable of developing memory for normal cell identification, abnormal cell and foreign body recognition, or defense mechanisms, and the patient would die. The inclusion of these criteria defines the immune system as "immunocompetent." Without the development of cell memory, re-exposure to an antigen will cause serious illness and, in some cases, death.

     Immune response is categorized into either cellular or humoral immunity. Cellular immunity is mediated by cells; humoral immunity is mediated by noncellular bodily fluids. In cellular immunity, the immune system cells envelop and deactivate or destroy the offending antigen. The majority of antigens are proteins. In humoral immunity, the biochemical substances in the body fluid deactivate or destroy the offending antigen through chemical processes. The mediators of the chemical attack are antibodies, or immunoglobulins.

     Immunoglobulins are created by particular cells of the immune system called B lymphocytes or B cells. There are five different classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM. The humoral immune response begins with the body's exposure to an antigen. Following exposure, antibodies are released from immune system cells and attach themselves to the invading substance to facilitate its removal from the body by other cells of the immune system.

     The circulatory system is key to the process, as it moves cells and antibodies throughout the body in conjunction with maintaining fluid volumes within the circulatory system. Failure to maintain the fluid volume balance will result in altered circulation, followed by shock. Just as the kidneys act to regulate volume within blood vessels, the lymphatic system acts to remove excess fluid from the tissues to maintain fluid volume balance. As the volume is pushed through the lymph system, it passes along the lymph nodes to provide the immune cells with an opportunity to identify antigens and subsequently adhere to the antigen for mitigation.

     If the immune system does not develop appropriate memory or does not function effectively, the patient will become immunocompromised. Conversely, an exaggerated immune response will lead to an untoward event including allergic reaction, autoimmune disease, sepsis or even cancer. Failure of the lymphatic system will create an environment where an infectious disease will flourish or normal fluid balance will be disrupted.

     The remainder of this article will highlight a few common disease processes influenced by the immune system.