| Acquired Immunity | Formation of antibodies after exposure to an antigen |
| Antibody (Ab) | Proteins produced by white blood cells in response to antigens |
| Antigen (Ag) | Foreign substance (protein) that stimulates the production of antibodies |
| Immunity | The body's ability to resist organisms and toxins |
| Immunoglobulins | Antibodies produced by plasma cells |
| Interstitial Fluid | Fluid in the paces between cells; extracellular fluid in tissues |
| Lymph | Watery fluid found in lymphatic vessels |
| Lymph Capillaries | Tiniest lymphatic vessels |
| Lymph Node | Stationary; bean-shaped structure along lymphatic vessels |
| Lymph Vessels | Vessels that carry lymph throughout the body |
| Macrophages | Monocytes that migrate from the blood to the tissue; large phagocytes |
| Spleen | Organ in the cranial abdomen that stores, produces, and destroys blood cells |
| Thymus Gland | Organ in the cranial mediastinum that produces and stores lymphocytes |
| Allergen | Substance that causes a specific hypersensitivity |
| Allergy | Abnormal hypersensitivity to an antigen |
| Anaphylaxis | Exaggerated hypersensitivity to a foreign substance |
| Autoimmune Disease | Disease in which the body makes antibodies against its own good cells and tissues |
| Carrier | An animal that harbors a disease without displaying signs of infection |
| Culture | Cultivation of microorganisms in special media |
| Edema | Excessive fluid in tissues |
| Febrile | Having a fever |
| Hypersplenism | Condition marked by splenomegaly and excessive cell destruction causing anemia, leukopenia, and thrombocytopenia |
| Immunosupression | Impaired immune response |
| Remission | Symptoms lessen and the patient feels better |
| Relapse | Symptoms return after an apparent recovery |
| Resistant | Does not easily affect; not susceptible |
| Retrovirus | RNA virus that multiplies by using the host's DNA |
| Sepis | Infection in the blood or other tissues |
| Toxin | A poison |
| Vaccine | Suspension containing a killed or weakened microorganism given via injection to induce immunity |
| Vaccination | Administration of a suspension containing a killed or weakened microorganism to induce immunity |
| Zoonotic | Disease capable of being transmitted from animals to humans |
