Immune System

These flashcards cover the key vocabulary terms and definitions related to the immune system, suitable for exam preparation.

Immune System

Body's defense network against pathogens, foreign substances, and abnormal cells.

Immunity

The ability to resist infection and disease.

Pathogen

Disease-causing microorganism (bacteria, virus, fungus, parasite).

Antigen

Any substance that triggers an immune response; typically foreign proteins or polysaccharides.

Antibody (Immunoglobulin)

Y-shaped protein produced by B cells that binds to specific antigens.

Innate Immunity

Non-specific, immediate defense mechanisms present from birth; first and second lines of defense.

Adaptive Immunity

Specific, slower immune response that develops after exposure to antigens; provides immunological memory.

Cell-Mediated Immunity

Adaptive immune response involving T cells that directly attack infected or abnormal cells.

Humoral Immunity

Adaptive immune response involving B cells and antibody production.

Active Immunity

Immunity developed when the body produces its own antibodies (through infection or vaccination).

Passive Immunity

Immunity acquired by receiving antibodies from another source (maternal antibodies, immunoglobulin injection).

Lymphocytes

White blood cells central to adaptive immunity; include B cells, T cells, and NK cells.

B Cells (B Lymphocytes)

Lymphocytes that mature in bone marrow and produce antibodies.

Plasma Cells

Activated B cells that secrete large quantities of antibodies.

T Cells (T Lymphocytes)

Lymphocytes that mature in the thymus and mediate cell-mediated immunity.

Helper T Cells (CD4+)

T cells that activate other immune cells and coordinate immune responses.

Cytotoxic T Cells (CD8+)

T cells that directly kill infected, cancerous, or foreign cells.

Regulatory T Cells (T suppressors)

T cells that suppress immune responses to prevent autoimmunity.

Memory Cells

Long-lived B and T cells that provide rapid response upon re-exposure to the same antigen.

Natural Killer (NK) Cells

Lymphocytes that kill virus-infected and cancerous cells without prior sensitization.

Phagocytes

Cells that engulf and destroy pathogens through phagocytosis.

Neutrophils

Most abundant white blood cells; first responders to bacterial infection.

Macrophages

Large phagocytes that engulf pathogens, dead cells, and debris; also present antigens.

Dendritic Cells

Antigen-presenting cells that capture antigens and activate T cells.

Monocytes

White blood cells that differentiate into macrophages and dendritic cells.

Eosinophils

White blood cells that combat parasitic infections and mediate allergic responses.

Basophils

White blood cells that release histamine during allergic reactions.

Mast Cells

Tissue-resident cells that release histamine and other inflammatory mediators.

Antigen-Presenting Cells (APCs)

Cells that display antigens on their surface to activate T cells (dendritic cells, macrophages, B cells).

MHC (Major Histocompatibility Complex) Molecules

Cell surface proteins that display antigens to T cells.

Complement System

Group of plasma proteins that enhance immune responses through pathogen lysis, opsonization, and inflammation.

Opsonization

Process of coating pathogens with antibodies or complement proteins to enhance phagocytosis.

Cytokines

Signaling proteins secreted by immune cells to regulate immune responses.

Interleukins

Cytokines that mediate communication between leukocytes.

Interferons

Cytokines that interfere with viral replication and activate immune cells.

Chemokines

Cytokines that attract immune cells to sites of infection or inflammation.

Inflammation

Localized protective response to tissue injury or infection; characterized by redness, heat, swelling, and pain.

Histamine

Chemical mediator released during inflammation and allergic reactions; causes vasodilation and increased vascular permeability.

Fever

Elevated body temperature that enhances immune function and inhibits pathogen growth.

Immunoglobulin Classes

Five types of antibodies with different functions.

Clonal Selection

Process by which an antigen selectively activates B and T cells with matching receptors.

Primary Immune Response

Initial adaptive immune response to first antigen exposure; slow, produces mainly IgM.

Secondary Immune Response

Faster, stronger adaptive response upon re-exposure to same antigen; produces mainly IgG.

Immunological Memory

Ability of the immune system to remember previous antigen exposures through memory cells.

Vaccination (Immunization)

Administration of antigens to stimulate adaptive immunity without causing disease.

Vaccine

Preparation containing antigens (killed/weakened pathogens or parts of pathogens) used for immunization.

Autoimmune Disease

Condition where the immune system attacks the body's own tissues.

Immunodeficiency

Condition of weakened or absent immune function.

Hypersensitivity

Excessive or inappropriate immune response.

Anaphylaxis

Severe, life-threatening allergic reaction causing systemic vasodilation and airway constriction.

Allergen

Substance that triggers an allergic reaction.

Transplant Rejection

Immune response against transplanted tissue with different MHC molecules.

Immunosuppression

Deliberate suppression of immune responses (used in transplantation and autoimmune diseases).