I
Occurring spontaneously or from an unknown cause.
Idiopathic Thrombocytopenia Purpura (ITP) 
(En español)
Also known as: Immune Thrombocytopenic Purpura
An autoimmune disorder in which the immune system destroys platelets. The destruction of platelets leads to abnormal blood clotting and easy or excessive bruising and bleeding. The exact cause of idiopathic thrombocytopenia purpura is unknown; however, the disorder may develop with a viral infection, including HIV.
See Related Term(s): Platelet
Also known as: Antigen-Antibody Complex
An antibody bound to an antigen. Immune complexes are part of a normal immune response. However, when immune complexes accumulate in the blood, they can cause autoimmune disorders, infections, and malignancies.
See Related Term(s): Antigen
Immune Reconstitution Inflammatory Syndrome (IRIS) (En español)
Also known as: Immune Reconstitution Syndrome, Immune Restoration Disease
In HIV infection, an exaggerated inflammatory reaction to a disease-causing microorganism that sometimes occurs when the immune system begins to recover following treatment with antiretroviral (ARV) drugs. Immune reconstitution inflammatory syndrome (IRIS) occurs in two forms: "unmasking" IRIS refers to the flare-up of an underlying, previously undiagnosed infection soon after antiretroviral therapy (ART) is started; "paradoxical" IRIS refers to the worsening of a previously treated infection after ART is started. IRIS can be mild or life-threatening.
Actions of the immune system to defend the body against bacteria, viruses, or other substances that the body recognizes as foreign and harmful.
See Related Term(s): Immune System
A complex network of specialized cells, tissues, and organs that recognize and defend the body from foreign substances, primarily disease-causing microorganisms such as bacteria, viruses, parasites, and fungi. Organs and tissues of the immune system, called lymphoid organs, include the bone marrow, spleen, thymus, and tonsils. Immune system cells include white blood cells, such as B lymphocytes (B cells), T lymphocytes (T cells), dendritic cells, and macrophages. HIV infection gradually destroys the immune system.
Protection against disease caused by infectious microorganisms or by other foreign substances. There are two main types of immunity: innate and acquired.
See Related Term(s): Acquired Immunity, Innate Immunity
When the body is able to produce a normal immune response.
See Related Term(s): Immune Response
When the body is unable to produce an adequate immune response. A person may be immunocompromised because of a disease or an infection, such as HIV, or as the result of treatment with drugs or radiation.
See Related Term(s): Immune Response
Inability to produce an adequate immune response because of an insufficiency or absence of antibodies, immune cells, or both. Immunodeficiency disorders can be inherited, such as severe combined immunodeficiency; they can be acquired through infection, such as with HIV; or they can result from chemotherapy.
See Related Term(s): Acquired Immunodeficiency Syndrome, Immune Response
The ability or the extent to which a substance is able to stimulate an immune response.
See Related Term(s): Immune Response
Pertaining to the immune system.
See Related Term(s): Immune System
A type of HIV treatment failure. There is no consensus on the definition of immunologic failure. However, some experts define immunologic failure as the failure to achieve and maintain adequate CD4 counts despite viral suppression.
See Related Term(s): Treatment Failure, Viral Suppression
A natural or synthetic substance that modifies (activates, enhances, or suppresses) the immune response or the functioning of the immune system.
See Related Term(s): Immune Response, Immune System
When the body's ability to mount an immune response to fight infections or disease is reduced. Immunosuppression may result from certain diseases, such as HIV/AIDS, or as a result of radiotherapy or chemotherapy. Immunosuppression may also be deliberately induced by drugs used to prevent rejection of transplanted organs.
See Related Term(s): Immune Response
Also known as: Immunomodulatory Therapy
Use of immunologic agents such as antibodies, growth factors, and vaccines to modify (activate, enhance, or suppress) the immune system in order to treat disease. Immunotherapy is also used to diminish adverse effects caused by some cancer treatments or to prevent rejection of a transplanted organ or tissue.
See Related Term(s): Immune System
In the uterus (womb).
In utero also refers to the length of time that a fetus is in the uterus of the pregnant female.
In an artificial environment outside the body, such as in a test tube in a laboratory.
In Vitro Fertilization (IVF) (En español)
A medical procedure used to help a woman become pregnant.
In vitro fertilization (IVF) involves removing mature eggs from a woman’s ovary, fertilizing the eggs with sperm in a laboratory, and then introducing the resulting embryo into a woman's uterus.
In the living body of a plant, animal, or human.
The number of new cases of a disease in a specific area during a specific time period.
See Related Term(s): Prevalence
The time between infection with a pathogen and the onset of disease symptoms.
See Related Term(s): Pathogen
Indian Health Service (IHS) (En español)
A federal agency responsible for providing federal health services to American Indians and Alaska Natives. The Indian Health Service (IHS) delivers preventive, curative, and community health care to American Indians and Alaska Natives in hospitals, clinics, and other settings throughout the United States.
Invasion and growth of an infectious microorganism, such as a bacterium or virus, in the body. Infection can also refer to the disease caused by the infectious microorganism. For example, HIV infection is caused by the human immunodeficiency virus (HIV).
Capable of causing infection.
A disease that is caused by a microorganism, such as a bacterium, virus, or parasite, that is not normally found in the body and is capable of causing infection. Some, but not all, infectious diseases are contagious, meaning they can spread from person to person. Other infectious diseases can spread from animals or insects to humans, but not from person to person. HIV is both infectious and contagious.
See Related Term(s): Contagious Disease
A communication process between a person and a health care provider or researcher to ensure that the person understands all relevant facts associated with a medical procedure or clinical trial. Before undergoing the procedure or participating in the trial, the person must sign an informed consent form that indicates understanding of the risks and benefits involved and of the risks and benefits of other options.
The Spanish-language companion Web site to AIDS
info. Information is available via the Web, phone, e-mail, and postal mail.
See Related Term(s): AIDSinfo
Administration of a substance, such as a drug or glucose in solution, typically into a vein (intravenous). Infusions can also be administered into bone (intraosseous), muscle (intramuscular), and the space that surrounds the spinal cord (epidural).
A method of illicit drug use. The drugs are injected directly into the body—into a vein, into a muscle, or under the skin—with a needle and syringe. Blood-borne viruses, including HIV and hepatitis, can be transmitted via shared needles or other drug injection equipment.
An adverse reaction, such as rash or redness, at the site of an injection.
Immunity that a person is born with. Innate immunity includes certain physical barriers, such as skin and mucous membranes, and fast-acting immune cells, such as natural killer cells.
See Related Term(s): Immunity
Institutional Review Board (IRB) (En español)
An independent committee of medical, scientific, and non-scientific members established to review, approve, and monitor research involving human participants. An institutional review board (IRB) protects the rights and welfare of human participants by assuring that a clinical trial is well designed, does not involve undue risks, and includes safeguards for participants. Any institution conducting or supporting research that involves human participants must appoint an IRB to monitor the research.
See Related Term(s): Clinical Trial
A hormone that is secreted by the pancreas and controls the amount of glucose in the blood. Glucose is the body’s main source of energy. Insulin stimulates cells to absorb and use glucose for energy. Without insulin, cells starve for energy and glucose builds up in the blood (hyperglycemia). Insulin also refers to the laboratory-made drug.
See Related Term(s): Diabetes, Glucose, Pancreas
The body's decreasing ability to respond to and use the insulin it produces. As a result, excess glucose builds up in the blood (hyperglycemia). Insulin resistance increases the risk of developing type 2 diabetes and heart disease. Use of certain antiretroviral (ARV) drugs may cause insulin resistance.
See Related Term(s): Diabetes, Insulin
The degree to which the body's cells respond to insulin and take up glucose from the blood.
See Related Term(s): Insulin
An enzyme found in HIV (and other retroviruses). HIV uses integrase to insert (integrate) its viral DNA into the DNA of the host cell. Integration is a crucial step in the HIV life cycle and is targeted by a class of antiretroviral (ARV) HIV drugs called integrase strand transfer inhibitors (INSTIs).
See Related Term(s): Integrase Strand Transfer Inhibitor, Integration, Life Cycle, Provirus
Integrase Strand Transfer Inhibitor (INSTI) (En español)
Also known as: Integrase Inhibitor
Antiretroviral (ARV) HIV drug class. Integrase strand transfer inhibitors (INSTIs) block integrase (an HIV enzyme). HIV uses integrase to insert (integrate) its viral DNA into the DNA of the host cell. Blocking integrase prevents HIV from replicating.
See Related Term(s): Drug Class, Integrase
Adding additional antiretroviral (ARV) drugs to an HIV regimen to further reduce replication of HIV.
Cytokines secreted by certain cells in response to an antigen, usually a virus. Interferon signals neighboring cells into action and inhibits the growth of malignant cells. There are three types of interferons: alpha, beta, and gamma. Laboratory-made interferons are used to treat certain cancers and opportunistic infections.
See Related Term(s): Antigen, Cytokine
A cytokine that stimulates the growth and replication of immune cells, specifically B lymphocytes (B cells) and T lymphocytes (T cells). Laboratory-made interleukin-2 (IL-2) is used to treat certain cancers.
See Related Term(s): Cytokine
A cytokine that prompts the immune system to make more B lymphocytes (B cells) and T lymphocytes (T cells). Laboratory-made interleukin-7 (IL-7) coupled with antiretroviral therapy (ART) is being studied as a potential treatment for HIV.
See Related Term(s): Cytokine
International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Group (En español)
A cooperative group of institutions, investigators, and other collaborators organized to evaluate treatment for HIV-infected children, adolescents, and pregnant women, including treatment and prevention of coinfections; to develop and evaluate safe and effective approaches to prevent mother-to-child transmission of HIV; and to evaluate vaccines for the prevention of HIV transmission among adolescents. International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Group was formed through a merger of investigators, including investigators from the Pediatric AIDS Clinical Trials Group (PACTG).
See Related Term(s): Clinical Trial, Pediatric AIDS Clinical Trials Group
International Network for Strategic Initiatives in Global HIV Trials (INSIGHT) (En español)
A clinical trials network that conducts studies worldwide in order to define optimal strategies for the management of HIV and other infectious diseases.
See Related Term(s): Clinical Trial
A kidney disorder in which the spaces between the kidney tubules (tiny urine-collecting tubes) become swollen. Interstitial nephritis can impair kidney function, including a kidney's ability to filter waste and extra fluid from the body.
See Related Term(s): Kidneys
A measure taken to prevent or treat disease or to improve health in other ways. Examples of interventions include preventive vaccines, drugs, and palliative care.
A type of clinical trial. In interventional trials, researchers assign participants to a treatment or other intervention and then measure outcomes.
See Related Term(s): Clinical Trial
Intracytoplasmic Sperm Injection (ICSI) (En español)
A type of
in vitro (outside the body) fertilization that is used principally to overcome male infertility. Intracytoplasmic sperm injection (ICSI) involves injecting a single sperm into an egg that has been removed from a woman’s ovary. The fertilized egg can then be returned to the woman's uterus. Sperm washing combined with ICSI can be considered as a reproductive option for an HIV discordant couple. ICSI is considered when the man is the HIV-infected partner and insemination with donor sperm from an HIV-uninfected male is not an option.
See Related Term(s): Discordant Couple, Sperm Washing
Within or between the layers of the skin. Some drugs are given as intradermal injections.
Situated or occurring inside a muscle. An intramuscular (IM) injection is an injection given directly into a muscle.
The time period spanning childbirth, from the onset of labor through delivery of the placenta. Intrapartum can refer to both the woman and the fetus.
Intrauterine Insemination (IUI) (En español)
Also known as: Artificial Insemination
A medical procedure used to help a woman become pregnant. Intrauterine insemination (IUI) involves placing sperm directly in a woman's uterus the day after ovulation. For a discordant couple in which the HIV-infected partner is female, IUI is the most effective way to reduce the risk of HIV transmission when trying to conceive.
See Related Term(s): Discordant Couple
Within or introduced into the vagina.
Situated or occurring inside a vein. An intravenous (IV) injection is an injection given directly into a vein.
Intravenous Immunoglobulin (IVIG) (En español)
Also known as: Immune Serum Globulin
A solution of antibodies prepared for injection into a person’s vein. Intravenous immunoglobulin (IVIG) is composed of antibodies removed from the blood of healthy donors and then pooled together and purified. IVIG is approved for use in children infected with HIV to reduce the risk of serious bacterial infections.
See Related Term(s): Antibody
Pertaining to an infection or disease that spreads to surrounding tissues or to other parts of the body. Invasive can also refer to a medical procedure that involves entering a part of the body, such as through an incision.
Also known as: Experimental Drug
A drug that is approved by the Food and Drug Administration (FDA) for testing in humans for a specified condition but not approved for commercial marketing and sale.
See Related Term(s): Food and Drug Administration
Investigational New Drug (IND) Application (En español)
A drug sponsor’s request to the Food and Drug Administration (FDA) for approval to test an investigational drug in humans. FDA review of an investigational new drug (IND) application ensures that the drug is safe for testing in humans and that testing will not put study participants at unreasonable risk.
See Related Term(s): Food and Drug Administration, Investigational Drug
A decrease in blood flow to an organ or tissue of the body, usually due to a blocked artery.
Also known as: Cystoisosporiasis
An intestinal infection caused by the protozoan parasite
Cystoisospora belli (formerly called
Isospora belli). Isosporiasis can be spread by ingesting food or water contaminated with the parasite. Symptoms of isosporiasis include watery diarrhea, abdominal pain, anorexia, and low-grade fever. In people with HIV, chronic isosporiasis (lasting over 1 month) is an AIDS-defining condition.
See Related Term(s): AIDS-Defining Condition, Opportunistic Infection