Lymphatic and Immune Systems

Lymph

clear watery fluid that surrounds body cells

Interstitial fluid

fluid found in the spaces between body cells; when it enters lymph capillaries

Lymphatic system

the network of lymph vessels

Lymph capillaries

tiny thin-walled tubes that begin in tissue spaces and collect lymph.

Lymph vessels

tubes with thicker walls and one-way valves that carry lymph toward the chest and back to the bloodstream.

Lymph nodes

small masses of lymphatic tissue located along lymph vessels that filter lymph and contain immune cells.

Cervical lymph nodes

lymph nodes located in the neck.

Axillary lymph nodes

lymph nodes located in the armpit.

Mediastinal lymph nodes

lymph nodes located in the central chest area between the lungs.

Mesenteric lymph nodes

lymph nodes located in the tissue that supports the intestines.

Paraaortic lymph nodes

lymph nodes located near the aorta.

Inguinal lymph nodes

lymph nodes located in the groin.

Macrophage

a large immune cell that engulfs and digests foreign substances

Phagocytosis

the process in which a cell surrounds

B lymphocyte (B cell)

an immune cell that matures in bone marrow and can become a plasma cell that produces antibodies.

T lymphocyte (T cell)

an immune cell that matures in the thymus and helps attack infected

Lymphocyte

a type of white blood cell involved in immune defense; major types include B cells

Monocyte

a large white blood cell that can enter tissues and develop into a macrophage or dendritic cell.

Spleen

a lymphatic organ that filters blood

Erythrocyte (RBC)

a red blood cell that carries oxygen.

Platelet

a small blood component that helps form clots and stop bleeding.

Thymus gland

a primary lymphoid organ in front of the heart and behind the sternum where T cells mature

Primary lymphoid organ

an organ where immune cells develop and mature; examples include the bone marrow and thymus.

Immunocompetent

able to recognize antigens and respond effectively as part of the immune system.

Immune system

the body’s defense system against harmful organisms

Immunity

the body’s ability to resist or fight organisms and toxins that can damage tissues and organs.

Natural immunity (innate immunity)

protection present at birth that acts quickly and does not require previous exposure to a specific antigen.

Acquired immunity (adaptive immunity)

specific protection that develops after exposure to an antigen through infection

Active immunity

immunity produced by a person’s own immune system after infection

Passive immunity

temporary immunity received from ready-made antibodies

Antigen

a foreign substance or molecule that triggers an immune response.

Antibody

a protein made by plasma cells that binds to a specific antigen and helps block or mark it for destruction.

Humoral immunity

antibody-based immunity involving B cells and plasma cells

Plasma cell

a mature B cell that produces and releases antibodies called immunoglobulins.

Immunoglobulin (Ig)

another name for an antibody; a protein that recognizes and binds to a specific antigen.

Cytotoxic T cell (CD8+ T cell)

a T cell that directly attaches to and kills infected

Helper T cell (CD4+ T cell)

a T cell that coordinates immune responses

Suppressor T cell (regulatory T cell or Treg)

a T cell that slows immune responses and helps prevent the immune system from attacking the body’s own cells.

Cytokine

a signaling protein released by immune cells that helps control and coordinate immune responses.

Interferon

a cytokine that helps cells resist viral infection and supports immune activity.

Interleukin

a cytokine that allows white blood cells to communicate and regulate immune responses.

Natural killer cell

an innate immune cell that destroys tumor cells and virus-infected cells without needing prior exposure.

Dendritic cell

an antigen-presenting immune cell that captures and digests foreign material and activates adaptive immune responses.

IgG

the most common antibody in blood plasma; it neutralizes toxins

IgM

usually the first antibody produced during a new immune response and an important antibody in early defense against infection.

IgA

an antibody that protects mucosal surfaces and is found in saliva

Colostrum

the first breast milk produced after childbirth; it is rich in IgA and other protective substances.

IgE

an antibody involved in allergic reactions and defense against some parasites.

IgD

an antibody mainly attached to B cells that helps with B-cell activation; its full function is less clearly understood.

Immunotherapy

treatment that stimulates

Vaccine

a preparation containing antigens or antigen-like material that trains the immune system to recognize and fight a disease or tumor.

Active immunotherapy

treatment that stimulates the patient’s own immune system to attack a target.

Passive immunotherapy

treatment that gives the patient immune substances

Monoclonal antibody (MoAb)

a laboratory-made antibody designed to bind to one specific target

Donor lymphocyte infusion

a treatment in which donor T cells are given after an allogeneic stem cell or bone marrow transplant to help attack remaining cancer cells.

Allogeneic transplant

a transplant using stem cells or bone marrow from another person.

Stem cell transplant

a procedure that replaces damaged or diseased blood-forming cells with healthy stem cells.

Bone marrow transplant

a type of stem cell transplant that replaces unhealthy blood-forming marrow cells.

Immunodeficiency

a condition in which the immune system is weakened or unable to fight infection normally.

Acquired immunodeficiency syndrome (AIDS)

the advanced stage of HIV infection in which severe loss of immune function makes a person vulnerable to opportunistic infections and certain cancers.

Human immunodeficiency virus (HIV)

the virus that attacks CD4+ helper T cells and can lead to AIDS if untreated.

Cellular immunity

immune protection mainly carried out by T cells and other immune cells rather than antibodies.

Opportunistic infection

an infection caused by organisms that usually do not cause serious disease in people with healthy immune systems but can become dangerous when immunity is weak.

Malignancy

cancer or a cancerous condition that can invade tissues and spread.

Wasting syndrome

unintended severe weight loss with muscle loss

Muscle atrophy

shrinking or wasting away of muscle tissue.

Kaposi sarcoma

a cancer associated with weakened immunity that causes red

In utero transmission

transmission from a pregnant mother to the fetus before birth.

Neonate

a newborn baby

Candidiasis

a fungal infection caused by Candida; in the mouth it is called thrush.

Thrush

a Candida yeast infection of the mouth that often causes white patches.

Cryptococcosis

a fungal infection caused by Cryptococcus that may affect the lungs

Cryptosporidiosis

an infection caused by the Cryptosporidium parasite that commonly affects the digestive tract and may become severe in immunocompromised patients.

Cytomegalovirus (CMV) infection

a viral infection that can cause serious disease such as inflammation of the intestines or retina in people with weak immune systems.

Enteritis

inflammation of the small intestine.

Retinitis

inflammation of the retina in the eye that can threaten vision.

Histoplasmosis

a fungal infection often acquired by breathing spores from soil contaminated with bird or bat droppings; it commonly affects the lungs.

Mycobacterium avium-intracellulare (MAI)

a group of bacteria that can cause serious lung or widespread bloodstream infection in people with advanced immune suppression.

Pneumocystis pneumonia (PCP)

a serious fungal lung infection that commonly affects people with severely weakened immune systems.

Toxoplasmosis

a parasitic infection that may be acquired from undercooked meat or contaminated material and can affect the brain and central nervous system.

Reverse transcriptase

a viral enzyme HIV uses to copy its genetic material inside human cells.

Reverse transcriptase inhibitor (RTI)

an antiretroviral drug that blocks reverse transcriptase and slows HIV reproduction.

Protease

an enzyme HIV uses to cut large proteins into smaller parts needed to build new virus particles.

Protease inhibitor

an antiretroviral drug that blocks HIV protease and prevents the virus from producing mature infectious particles.

Antiretroviral therapy (ART)

treatment with medicines that suppress HIV reproduction and help protect the immune system.

HAART (highly active antiretroviral therapy)

an older term for combination antiretroviral therapy using multiple HIV medicines from different drug classes.

Hypersensitivity

an excessive or inappropriate immune reaction to a substance.

Allergy

an abnormal immune sensitivity that develops after exposure to an antigen called an allergen.

Allergen

a normally harmless substance that triggers an allergic reaction in a sensitive person.

Allergic rhinitis (hay fever)

an allergic reaction in the nose causing sneezing

Anaphylaxis

a sudden severe allergic reaction that can cause breathing difficulty

Atopic dermatitis

a chronic itchy inflammatory skin condition also called eczema; triggers may include soaps

Urticaria (hives)

raised itchy welts on the skin

Atopy

an inherited tendency to develop allergic conditions such as allergic rhinitis

Lymphoma

a malignant tumor of lymphocytes or lymphatic tissue.

Hodgkin disease (Hodgkin lymphoma)

a lymphoma identified by characteristic Reed-Sternberg cells

Reed-Sternberg cell

a large abnormal cell that is a key finding in classical Hodgkin lymphoma.

Non-Hodgkin lymphoma

a broad group of lymphatic cancers that do not have the typical Reed-Sternberg cells of Hodgkin lymphoma.

Follicular lymphoma

a usually slow-growing type of non-Hodgkin lymphoma that develops from B cells in lymph node follicles.

Large cell lymphoma

a type of non-Hodgkin lymphoma made of large abnormal lymphocytes; many forms grow quickly.