Immunodeficiency disorders - Secondary: Nursing

Secondary immunodeficiencies are acquired disorders that occur as a result of some extrinsic factor affecting the immune system.

Let’s start with some immune system physiology. The immune system consists of white blood cells that protect us from pathogens, like viruses, bacteria, and fungi; but, also, foreign substances, such as toxins and chemicals, and destroy abnormal cells, such as those that might develop into cancer.

Now, the immune system consists of two main branches: innate immunity and adaptive immunity. The innate immune response involves non-specific defense mechanisms, meaning they don’t differentiate one pathogen from another. These include complement proteins and cells like phagocytes and natural killers; as well as dendritic cells, which activate the adaptive immune response. The adaptive immune response is highly specific, meaning that it recognizes different pathogens and is mediated by cells called lymphocytes, which include T and B cells.

T cells can be further divided into CD4+ and CD8+ T cells. CD4+ T cells are also known as T helper cells, because they interact with dendritic cells, and in turn help activate the rest of the lymphocytes. On the other hand, CD8+ T cells, also known as cytotoxic T cells, are in charge of cell-mediated immunity, where they attack abnormal cells. Finally, B cells mediate a specific adaptive response, called humoral immunity, by secreting antibodies that bind to and destroy extracellular antigens. These antibodies can be classified into several classes, including IgA, IgG, IgM, and IgE.

Now, there are several causes of secondary immunodeficiency, including calorie and protein malnutrition; adverse environmental conditions, like UV light, extreme cold, or high altitude; surgery and trauma; and medications, such as glucocorticoids, chemotherapy, and immunosuppressive agents used to treat autoimmune disorders or to prevent organ transplant rejection.