B Cells
See: B Lymphocytes

B-Cell Lymphoma
A type of cancer of the lymphatic tissue. People with HIV are more prone to non-Hodgkin's and other B-cell lymphomas, some of which are considered AIDS-defining conditions in people with HIV.
See Also:   Lymphoma
                   Non-Hodgkin's Lymphoma

B Lymphocytes (B Cells)
Also known as B cells. Infection-fighting white blood cells that develop in the bone marrow and spleen. B lymphocytes produce antibodies. In people with HIV, the ability of B lymphocytes to do their job may be damaged.
See Also:   Antibody

B2M
See: Beta-2 Microglobulin

Bactericide
A natural or man-made substance that kills bacteria.

Bacteriostatic
A natural or man-made substance that can prevent bacteria from reproducing, but cannot actually kill existing bacteria.

Bacterium
A microscopic organism consisting of one simple cell. Bacteria occur naturally almost everywhere on earth, including in soil, on skin, in the human gastrointestinal tract, and in many foods. Some bacteria can cause disease in humans.

Baseline
An initial measurement (for example, CD4 count or viral load) made before starting treatment or therapy for a disease or condition. In people infected with HIV, the baseline measurement is used as a reference point to monitor HIV infection.

Basophil
An infection-fighting white blood cell that causes inflammation in response to a micro-organism or other foreign invader.

bDNA Assay
See: Branched Chain DNA Assay

Beta-2 Microglobulin (B2M)
A protein found on the surface of white blood cells. Increased production or destruction of white blood cells causes B2M levels in the blood to increase. This increase is seen in people with cancers involving white blood cells and in people with advanced HIV disease.

b.i.d.
Twice a day dosing instructions.

Bilirubin
A yellowish substance excreted by the liver. Its measurement can be used as an indication of the health of the liver. Large quantities of bilirubin may cause the skin to take on a yellow tint (jaundice), and very high levels may cause brain damage.

Bioavailability
Rate and extent to which a drug is absorbed and available in the tissues of the body.

Biological Response Modifiers (BRMs)
Natural or man-made substances that can boost, direct, or restore immune system function.

Biopsy
The surgical removal and examination of an organ or tissue to aid in diagnosis and treatment of a health condition.

Black Box Warning
Information found at the beginning of a drug's prescribing information, manufacturer labeling, and promotional material. This information highlights important safety information, such as serious side effects, drug interactions, or use restrictions. The black box warning is one of the strongest warnings issued by the Food and Drug Administration (FDA), and is reserved for drugs with significant risks or monitoring requirements.

Blip
A temporary increase in viral load in someone who previously had undetectable virus and who later returns to having undetectable virus. The viral load during a blip is usually low (50 to 500 copies/mL).
See Also:   Undetectable Viral Load

Blood-Brain Barrier
A selective obstacle between circulating blood and brain tissues that prevents damaging substances from reaching the brain. Certain substances easily cross the blood-brain barrier; others are completely blocked.

Body Habitus Changes
Abnormal changes in the body's physical characteristics.
See Also:   Wasting Syndrome
                   Lipoatrophy
                   Lipohypertrophy

Bone Marrow Suppression
See:    Myelosuppression

Booster
An additional dose or doses of a vaccine taken after the initial dose to enhance the immune response to the vaccine. Also used as a term to describe a medicine given to enhance another medicine, such as using ritonavir (RTV) as a "booster" for other PIs.

Branched Chain DNA Assay (bDNA Assay)
A test that measures a person's viral load (level of HIV RNA in the blood) to identify HIV infection and monitor disease progression and treatment effectiveness. Results are reported as number of HIV RNA copies per mL of blood. bDNA assay is an alternative to measuring viral load by reverse transcriptase-polymerase chain reaction (RT-PCR).
See Also:   Reverse Transcriptase-Polymerase Chain Reaction
                   Viral Load

BRMs
See: Biological Response Modifiers

Bronchoscopy
Visual examination of the bronchial passages of the lungs using an endoscope (a curved, flexible tube containing fibers that carry light down the tube and project an enlarged image of the bronchial passages onto a viewing screen). Can also be used for extraction of material from the lungs.

Budding
The final step in the HIV life cycle, when an individual virus pushes out ("buds") from the host cell, stealing part of the cell's outer envelope and freeing itself to attach to and infect another host cell.

Buffalo Hump
See:    Dorsocervical Fat Pad

Burkitt's Lymphoma
Also know as small noncleaved cell lymphoma. A type of non-Hodgkin's B-cell lymphoma that occurs more frequently in immunocompromised people, such as those infected with HIV.
See Also:   Non-Hodgkin's Lymphoma