Immunodeficiency

Immunodeficiency, often called immunocompromise, occurs when the immune system cannot function correctly. In this state, the body's ability to fight infectious diseases or detect cancer is compromised. A person living with this condition is described as immunocompromised. This weakness makes individuals vulnerable to opportunistic infections. These are infections that typically do not harm healthy people. It also reduces cancer immunosurveillance. This is the process where the immune system scans the body to find and kill neoplastic, or cancerous, cells.

Doctors categorize immunodeficiencies into two main types: primary and secondary. Primary immunodeficiencies, also known as congenital immunodeficiencies, are present from birth. These are often hereditary and result from genetic flaws. There are over 95 recognized primary immunodeficiency syndromes. These are usually grouped by the specific part of the immune system that is malfunctioning. Examples include disorders affecting lymphocytes or granulocytes. Secondary immunodeficiencies are acquired later in life. These result from external factors or other diseases.

Many different factors can cause a secondary immunodeficiency. Infections like HIV can cause acquired immune deficiency syndrome (AIDS). HIV directly infects T helper cells and impairs other immune responses. Environmental factors like malnutrition or toxins such as mercury can also be causes. Even lifestyle factors like heavy alcohol use or smoking can depress immune responses. In clinical settings, doctors sometimes use immunosuppression as a treatment. Drugs like steroids or chemotherapy can lower immune function. This is often intended to prevent organ transplant rejection or to treat autoimmune diseases.

Immunodeficiencies can affect many specific components of the immune system. Humoral immune deficiency involves B cells or antibodies. This can lead to hypogammaglobulinemia, which is a decrease in one or more antibodies. A more severe version is agammaglobulinemia, where most antibody production is missing. T cell deficiency is another type that can lead to AIDS. Some people suffer from granulocyte deficiency. This includes neutropenia, which is a low number of neutrophil granulocytes. Other types include asplenia, where the spleen does not function, or complement deficiency.

Antibodies, or immunoglobulins, are essential for fighting pathogens. There are five main classes: IgA, IgD, IgE, IgM, and IgG. IgG is a major antibody in the blood and can cross the placenta. This is vital during the antibody vulnerability period in children. This period lasts from birth until about three or four years of age. During this time, babies rely on maternal IgG for protection. Other antibodies like IgA are found in mucus, tears, and saliva. IgM is the main antibody for primary immune responses. IgE is mainly involved in allergic reactions and fighting parasites.

Some immunodeficiencies are linked to autoimmune diseases. This happens when the immune system is constantly activated but cannot clear infections. For example, common variable immunodeficiency (CVID) can lead to inflammatory bowel disease. X-linked agammaglobulinemia (XLA) is associated with autoimmune diseases like type 1 diabetes. Chronic granulomatous disease (CGD) involves a lack of NADPH oxidase in neutrophils. This causes chronic inflammation in the lungs and gut. These complex connections show how the immune system's balance is delicate.

Diagnosing an immunodeficiency requires several careful steps. A physician starts by reviewing a patient's medical and family history. They look for inherited conditions or past illnesses. A physical examination helps identify specific symptoms. Blood tests are then used to provide detailed data. These tests can measure white blood cell counts or antibody levels. Once the specific defect is found, treatment can begin. Treatments may include antibody infusions or long-term antibiotics. In some severe cases, a stem cell transplantation may be necessary to restore function.