Immunodeficiencies can be primary (genetic) or secondary (acquired). They weaken the body's defense against infections, making people more susceptible to illnesses. Primary immunodeficiencies are present from birth, while secondary ones develop later due to factors like HIV or malnutrition.
Different types of immunodeficiencies affect various parts of the immune system. For example, chronic granulomatous disease impairs phagocyte function, while X-linked agammaglobulinemia affects antibody production. Understanding these conditions helps in diagnosing and treating patients with weakened immune systems.
Primary and Secondary Immunodeficiencies
Primary vs secondary immunodeficiencies
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- Primary immunodeficiencies are caused by genetic defects present from birth or early childhood lead to increased susceptibility to infections, recurrent and severe infections, and impaired immune response to specific pathogens
- Secondary immunodeficiencies are acquired later in life due to external factors or underlying conditions (HIV/AIDS, malnutrition) result in weakened immune response, increased susceptibility to opportunistic infections, and impaired ability to fight off infections effectively
Types of primary immunodeficiencies
- Chronic granulomatous disease (CGD) involves a defect in phagocyte function causing inability of phagocytes to produce reactive oxygen species (ROS) impairing killing of ingested microorganisms leads to recurrent bacterial and fungal infections and formation of granulomas in affected tissues
- X-linked agammaglobulinemia (XLA) is a deficiency in antibody production caused by a mutation in the BTK gene on the X chromosome affects B cell development and maturation resulting in absence or extremely low levels of immunoglobulins (antibodies) increases susceptibility to bacterial infections, particularly with encapsulated bacteria (Streptococcus pneumoniae, Haemophilus influenzae)
Causes of secondary immunodeficiencies
- HIV/AIDS causes destruction of CD4+ T cells impairing cell-mediated immunity increases susceptibility to opportunistic infections (Pneumocystis pneumonia, Candida albicans)
- Malnutrition leads to deficiencies in essential nutrients (protein, zinc, vitamin A) impairing immune cell function and antibody production increases susceptibility to infections, particularly in developing countries
- Immunosuppressive drugs used to prevent organ rejection in transplant patients or treat autoimmune diseases suppress immune cell function and antibody production increasing risk of opportunistic infections (cytomegalovirus CMV, Epstein-Barr virus EBV)
- Certain cancers like hematologic malignancies (leukemia, lymphoma) impair immune cell function due to the cancer itself or chemotherapy treatment increasing susceptibility to bacterial, fungal, and viral infections
Components of the immune system affected by immunodeficiencies
- Innate immunity: The first line of defense against pathogens, including physical barriers, phagocytes, and the complement system
- Adaptive immunity: The specific immune response involving T and B lymphocytes, which can be impaired in various immunodeficiencies
- Complement system: A group of proteins that enhance the ability of antibodies and phagocytes to clear pathogens, which can be deficient in some primary immunodeficiencies
- Antigen presentation: The process by which immune cells display foreign antigens to T cells, crucial for initiating an adaptive immune response
- Opportunistic infections: Infections caused by organisms that typically do not cause disease in individuals with healthy immune systems, but can be severe in immunocompromised patients
Key Terms to Review (81)
Acquired immunodeficiency syndrome (AIDS): Acquired Immunodeficiency Syndrome (AIDS) is a chronic, potentially life-threatening condition caused by the human immunodeficiency virus (HIV). It severely weakens the immune system, making the body susceptible to opportunistic infections and certain cancers.
Activation of B cells: Activation of B cells is the process by which B lymphocytes recognize an antigen, leading to their proliferation and differentiation into plasma cells that produce antibodies. This activation is crucial for the humoral immune response.
Adaptive immunity: Adaptive immunity is a specialized immune response that develops over time, involving the activation and clonal expansion of lymphocytes. It provides long-lasting protection and memory against specific pathogens.
Anti-AChR antibodies: Anti-AChR antibodies are autoantibodies directed against acetylcholine receptors on the neuromuscular junction. They play a crucial role in the pathogenesis of myasthenia gravis by impairing neuromuscular transmission.
Apoptosis: Apoptosis is a form of programmed cell death that occurs in multicellular organisms. It plays a crucial role in regulating immune responses and maintaining cellular homeostasis.
Aspergillus: Aspergillus is a genus of mold commonly found in the environment that can cause infections, particularly in immunocompromised individuals. These fungi are known for producing conidia, which can be inhaled and lead to respiratory issues.
B-cell maturation: B-cell maturation is the process through which B-cells develop and differentiate in the bone marrow and peripheral lymphoid tissues. This process is crucial for the adaptive immune response, enabling B-cells to produce antibodies.
Bone marrow transplant: A bone marrow transplant is a medical procedure that replaces damaged or destroyed bone marrow with healthy bone marrow stem cells. It is often used to treat certain cancers and disorders of the blood and immune system.
Bone marrow ablation: Bone marrow ablation is a medical procedure that involves the destruction of bone marrow cells, typically using chemotherapy or radiation. It is often performed prior to a bone marrow transplant to eliminate diseased or cancerous cells and make room for healthy donor cells.
Bruton X-linked agammaglobulinemia: Bruton X-linked agammaglobulinemia (XLA) is a genetic disorder where B cells are absent, leading to a lack of immunoglobulins. It results in severe immune deficiency, making individuals highly susceptible to infections.
Bruton: Bruton is a reference to X-linked agammaglobulinemia (XLA), a genetic disorder where the body cannot produce enough B cells, leading to a severe lack of antibodies and increased susceptibility to infections. It primarily affects males due to its X-linked inheritance pattern.
CD4 T cells: CD4 T cells are a type of white blood cell that play a crucial role in the immune system by helping to coordinate the body's response to infections. They are also known as helper T cells and are essential in fighting off both viral and bacterial infections.
Chemotherapy: Chemotherapy is the use of chemical substances to treat diseases, particularly cancer and infections. It often targets rapidly dividing cells, including pathogens and malignant cells.
Chromobacterium violaceum: Chromobacterium violaceum is a Gram-negative, facultative anaerobic bacterium found in soil and water of tropical and subtropical regions. It is known for producing a violet pigment called violacein and can cause opportunistic infections in humans.
Chronic myelogenous leukemia: Chronic myelogenous leukemia (CML) is a type of cancer that originates in the bone marrow and leads to the overproduction of white blood cells. It is characterized by the presence of the Philadelphia chromosome, a genetic abnormality.
Chronic granulomatous disease: Chronic granulomatous disease (CGD) is a genetic disorder where phagocytes, a type of immune cell, are unable to effectively kill certain bacteria and fungi. This results in the formation of granulomas, which are clusters of immune cells that attempt to contain the infection.
CML: Chronic Myeloid Leukemia (CML) is a type of cancer that originates in the bone marrow and results in the overproduction of abnormal white blood cells. It is associated with a specific genetic abnormality called the Philadelphia chromosome.
Complement system: The complement system is a group of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens from an organism. It forms part of the innate immune response and also helps bridge innate and adaptive immunity.
Cytokines: Cytokines are small proteins released by cells, especially those of the immune system, that have a specific effect on interactions and communications between cells. They play crucial roles in regulating immune responses and inflammation.
Diabetes mellitus: Diabetes mellitus is a chronic metabolic disorder characterized by high blood glucose levels resulting from defects in insulin secretion, insulin action, or both. It can lead to various complications affecting multiple body systems.
E. coli: Escherichia coli (E. coli) is a gram-negative, rod-shaped bacterium commonly found in the lower intestine of warm-blooded organisms. While most strains are harmless, some can cause serious food poisoning and infections.
Escherichia coli: Escherichia coli (E. coli) is a Gram-negative, rod-shaped bacterium commonly found in the intestines of warm-blooded organisms. While most strains are harmless, some can cause serious food poisoning and infections.
Extracellular pathogens: Extracellular pathogens are microorganisms, such as bacteria and fungi, that reside outside the host's cells and cause infections. They elicit immune responses primarily involving antibodies and phagocytic cells.
Granuloma: A granuloma is an organized collection of immune cells formed in response to chronic inflammation, often due to persistent pathogens or foreign substances. It serves to isolate the offending agent but can also contribute to tissue damage.
Giardia lamblia: Giardia lamblia is a unicellular eukaryotic parasite that causes giardiasis, a common gastrointestinal infection. It primarily inhabits the small intestine of humans and other mammals.
Gastrointestinal tract: The gastrointestinal tract (GI tract) is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. It plays a crucial role in digestion and immune function.
Haemophilus influenzae: Haemophilus influenzae is a Gram-negative bacterium that can cause various infections, particularly in the respiratory tract. It is known for causing severe diseases such as meningitis and pneumonia, especially in young children and immunocompromised individuals.
Hepatitis: Hepatitis is an inflammation of the liver often caused by viral infections. It can lead to liver damage, cirrhosis, or liver cancer.
HIV: HIV (Human Immunodeficiency Virus) is a virus that targets the immune system, specifically CD4 cells (T cells), leading to a progressive failure of the immune system. If left untreated, HIV can lead to AIDS (Acquired Immunodeficiency Syndrome).
HIV infection: HIV infection is caused by the human immunodeficiency virus, which attacks and weakens the immune system, specifically targeting CD4+ T cells. If untreated, it can progress to AIDS (Acquired Immunodeficiency Syndrome), a severe condition where the immune system is heavily compromised.
Immunodeficiency: Immunodeficiency is a condition where the immune system's ability to fight infectious disease and cancer is compromised or entirely absent. It can be congenital (primary) or acquired (secondary).
Immunoglobulins: Immunoglobulins are specialized glycoproteins produced by B cells that function as antibodies in the immune response. They play a critical role in identifying and neutralizing pathogens such as bacteria and viruses.
Lymphopenia: Lymphopenia is a condition characterized by an abnormally low level of lymphocytes in the blood. It can result from various factors, including infections, autoimmune diseases, or immunodeficiency disorders.
Macrophages: Macrophages are large phagocytic cells derived from monocytes that play a crucial role in both innate and adaptive immunity. They engulf and digest pathogens, dead cells, and cellular debris.
Malnutrition: Malnutrition is a condition resulting from an imbalanced intake of nutrients, either through deficiency or excess. It can severely impact the immune system's functionality and lead to immunodeficiency.
Neutrophils: Neutrophils are a type of white blood cell that play a crucial role in the innate immune response. They are the first responders to microbial infection and are highly active in phagocytosis.
NADPH oxidase: NADPH oxidase is an enzyme complex found in phagocytes that produces reactive oxygen species (ROS) to combat pathogens. It plays a crucial role in the immune response by generating superoxide radicals during the respiratory burst.
Phagocytes: Phagocytes are immune cells that engulf and digest pathogens, cellular debris, and foreign particles. They play a crucial role in both innate and adaptive immunity.
Pyroptosis: Pyroptosis is a type of programmed cell death associated with inflammation, typically triggered by infections or immune responses. It involves the activation of inflammatory caspases leading to cell lysis and release of pro-inflammatory cytokines.
Radiation therapy: Radiation therapy is a medical treatment that uses high doses of radiation to kill or shrink cancer cells by damaging their DNA. It can also impact normal cells, including those of the immune system, potentially leading to immunodeficiency.
Salmonella typhimurium: Salmonella typhimurium is a gram-negative bacterium that causes gastroenteritis in humans. It is commonly used in research to study bacterial pathogenesis and host immune response.
Severe combined immunodeficiency (SCID): Severe Combined Immunodeficiency (SCID) is a group of rare genetic disorders characterized by the severe impairment or absence of functional T and B lymphocytes. This results in extreme vulnerability to infections from infancy.
Secondary immunodeficiency: Secondary immunodeficiency is an acquired condition resulting from external factors that impair the immune system. It differs from primary immunodeficiency, which is genetic.
Serratia marcescens: Serratia marcescens is a Gram-negative, rod-shaped bacterium known for producing a characteristic red pigment called prodigiosin. It can be an opportunistic pathogen involved in hospital-acquired infections and can affect the respiratory and urinary tracts.
Staphylococcus aureus: Staphylococcus aureus is a Gram-positive bacterium commonly found on the skin and in the nasal passages. It can cause a range of infections from minor skin conditions to severe diseases like pneumonia and sepsis.
SCID: SCID (Severe Combined Immunodeficiency) is a primary immunodeficiency disorder characterized by the disturbed development of functional T cells and B cells. It results in severe, life-threatening infections due to an extremely compromised immune system.
Selective IgA deficiency: Selective IgA deficiency is an immune disorder characterized by a lack of Immunoglobulin A (IgA) antibodies, which play a crucial role in mucosal immunity. It is the most common primary immunodeficiency.
Superoxide radicals: Superoxide radicals are highly reactive molecules containing an extra electron, making them potent agents of cellular damage. They play a crucial role in immune responses but can also contribute to immunodeficiency when not properly regulated.
Streptococcus pneumoniae: Streptococcus pneumoniae is a Gram-positive bacterium often found in the human respiratory tract, capable of causing diseases such as pneumonia, meningitis, and sinusitis. It exhibits virulence factors like a polysaccharide capsule that help it evade the immune system.
T-cell dependent antibody response: A T-cell dependent antibody response is an immune reaction where B cells require assistance from helper T cells to produce antibodies against a specific antigen. This process is essential for generating a strong and long-lasting immune memory.
Tyrosine kinase: Tyrosine kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP to a tyrosine residue in a protein. This phosphorylation event plays a crucial role in signaling pathways regulating cell division, growth, and immune responses.
Vaccine: A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. It typically contains an agent resembling a disease-causing microorganism, often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins.
X-linked SCID: X-linked Severe Combined Immunodeficiency (X-linked SCID) is a genetic disorder characterized by a severely compromised immune system. It is caused by mutations in the IL2RG gene, which affects T cells, B cells, and natural killer (NK) cells.
HAART: HAART, or Highly Active Antiretroviral Therapy, is a combination of multiple antiretroviral drugs used to treat HIV infection. It is a critical component in the management of immunodeficiency disorders, as well as a mechanism of action for certain antimicrobial drugs.
Pneumocystis jirovecii: Pneumocystis jirovecii is an opportunistic fungal pathogen that can cause a severe form of pneumonia, known as Pneumocystis pneumonia (PCP), in individuals with weakened immune systems. This microscopic fungus primarily infects the alveoli, or air sacs, of the lungs, leading to respiratory distress and potentially life-threatening complications.
AIDS: AIDS, or Acquired Immunodeficiency Syndrome, is a chronic and potentially life-threatening condition caused by the human immunodeficiency virus (HIV). It is characterized by the progressive destruction of the immune system, leading to increased susceptibility to opportunistic infections and certain cancers that can ultimately prove fatal if left untreated.
Complement System: The complement system is a complex network of proteins that work together as part of the immune system's chemical defenses. It is a crucial component of the body's innate and adaptive immune responses, playing a vital role in inflammation, pathogen elimination, and the clearance of immune complexes.
Innate Immunity: Innate immunity refers to the body's natural, non-specific defense mechanisms that provide immediate protection against pathogens. It is the first line of defense against infectious agents and plays a crucial role in maintaining overall immune function.
T Cells: T cells, also known as T lymphocytes, are a type of white blood cell that play a crucial role in the adaptive immune response. They originate from stem cells in the bone marrow and mature in the thymus gland, developing specialized functions to recognize and eliminate threats to the body.
Cytokines: Cytokines are a diverse group of small proteins secreted by various cells, primarily immune cells, that act as signaling molecules to coordinate and regulate immune responses, inflammation, and other physiological processes. They play a crucial role in cellular defenses, pathogen recognition, inflammation, adaptive immunity, and various immune-related disorders and conditions.
Lymphocytes: Lymphocytes are a type of white blood cell that play a crucial role in the body's immune response. They are responsible for recognizing and responding to foreign invaders, such as bacteria, viruses, and other pathogens, as well as abnormal cells within the body.
B Cells: B cells, also known as B lymphocytes, are a type of white blood cell that play a crucial role in the adaptive immune response. They are responsible for the production of antibodies, which recognize and bind to specific foreign antigens, neutralizing them or marking them for destruction by other immune cells.
Neutrophils: Neutrophils are a type of white blood cell that play a crucial role in the body's innate immune response. They are the most abundant type of white blood cells and are the first responders to sites of infection or inflammation, acting as the body's primary defense against bacterial and fungal pathogens.
Adaptive Immunity: Adaptive immunity is the specialized, antigen-specific immune response that develops over time to combat specific pathogens more effectively. It involves the activation and proliferation of lymphocytes, particularly T cells and B cells, to recognize and neutralize or destroy foreign invaders.
Antigen Presentation: Antigen presentation is the process by which specialized immune cells, such as antigen-presenting cells (APCs), display fragments of foreign or self-antigens on their surface for recognition by T lymphocytes. This process is crucial for the initiation and regulation of the adaptive immune response against pathogens or altered self-cells.
Antibodies: Antibodies are specialized proteins produced by the immune system to recognize and neutralize foreign substances, such as bacteria, viruses, and other pathogens. They play a crucial role in the body's specific adaptive immune response, as well as in vaccine effectiveness and the development of hypersensitivities and immunodeficiencies.
CD4+ T cells: CD4+ T cells, also known as helper T cells, are a type of lymphocyte that plays a crucial role in the adaptive immune response. These cells express the CD4 co-receptor on their surface, which helps them recognize and respond to antigens presented by major histocompatibility complex (MHC) class II molecules on the surface of antigen-presenting cells.
Immunoglobulins: Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma B cells that recognize and bind to specific antigens, initiating an immune response. They play a crucial role in the humoral immune system and are involved in various immunological processes described in the topics of 18.2 Major Histocompatibility Complexes and Antigen-Presenting Cells, 18.4 B Lymphocytes and Humoral Immunity, 19.4 Immunodeficiency, and 20.5 Fluorescent Antibody Techniques.
Genetic Screening: Genetic screening is the process of identifying genetic variations or abnormalities in an individual's DNA to detect the presence or risk of certain genetic disorders or predispositions. It is a crucial tool in the context of immunodeficiency, as it can help identify individuals with genetic factors that may contribute to or increase the risk of developing immune system disorders.
Immunodeficiencies: Immunodeficiencies are disorders of the immune system that result in a decreased ability to fight infections and diseases. These conditions can be caused by genetic defects, acquired illnesses, or environmental factors that impair the normal function of the immune system.
Chronic granulomatous disease: Chronic granulomatous disease (CGD) is a rare inherited disorder characterized by the immune system's inability to effectively kill certain types of bacteria and fungi. This defect in the phagocytic cells, such as neutrophils and macrophages, leads to the formation of granulomas, which are collections of immune cells that accumulate at sites of infection or inflammation.
Bone Marrow Transplantation: Bone marrow transplantation is a medical procedure in which healthy bone marrow is transplanted into a patient to replace damaged or destroyed marrow. This procedure is often used to treat various types of immunodeficiencies, as it can restore the body's ability to produce functional immune cells.
Immunophenotyping: Immunophenotyping is the process of identifying and characterizing cells based on their expression of specific cell surface markers or antigens. It is a powerful tool used in the diagnosis and monitoring of various immunological disorders and diseases.
X-linked agammaglobulinemia: X-linked agammaglobulinemia (XLA) is a rare genetic disorder characterized by a deficiency in the production of functional B cells, leading to a severe reduction in all classes of antibodies (immunoglobulins). This immunodeficiency leaves individuals with XLA highly susceptible to recurrent and severe bacterial infections.
DiGeorge syndrome: DiGeorge syndrome is a genetic disorder characterized by the incomplete development of several body structures, primarily affecting the heart, face, and immune system. It is caused by a deletion or abnormality in a specific region of chromosome 22, leading to a range of health issues and increased susceptibility to infections.
BTK gene: The BTK gene, also known as the Bruton's tyrosine kinase gene, is a gene that plays a crucial role in the development and function of the immune system. It is responsible for the production of a protein called Bruton's tyrosine kinase, which is essential for the maturation and activation of B cells, a type of white blood cell that produces antibodies to fight infections.
Pneumocystis pneumonia: Pneumocystis pneumonia is a type of pneumonia caused by the fungus Pneumocystis jirovecii (formerly known as Pneumocystis carinii). It is a common opportunistic infection that primarily affects individuals with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive treatments.
Opportunistic Infections: Opportunistic infections are infections caused by pathogens that normally do not cause disease in individuals with a healthy, functioning immune system, but can take advantage of weakened or compromised immunity to cause illness. These infections are a significant concern in individuals with immunodeficiencies, such as those with HIV/AIDS, cancer, or organ transplants, who are more susceptible to developing these types of infections.
Wiskott-Aldrich Syndrome: Wiskott-Aldrich syndrome is a rare, inherited primary immunodeficiency disorder characterized by a triad of symptoms: thrombocytopenia (low platelet count), eczema, and recurrent infections. It is caused by a genetic mutation that affects the function of the immune system, leading to increased susceptibility to various infections and other complications.
Cytomegalovirus: Cytomegalovirus (CMV) is a type of herpes virus that can infect and remain dormant within the human body. It is a significant concern for individuals with weakened immune systems, as it can cause severe and potentially life-threatening infections.
Epstein-Barr Virus: Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that primarily infects and establishes lifelong latent infection in B lymphocytes. It is associated with various clinical manifestations, including infectious mononucleosis, autoimmune disorders, and immunodeficiency.