The Immune System: Innate and Adaptive Body Defenses

This set of flashcards covers key terms and concepts related to the immune system, including both innate and adaptive defenses.

Immune System

System that provides resistance against disease-causing microorganisms such as bacteria, fungi, and viruses.

First Line of Defense

Surface barriers that include intact skin and mucosae designed to keep pathogens out.

Second Line of Defense

Innate internal defenses that respond to pathogens when the first line is breached, relying on mechanisms such as inflammation and phagocytes.

Third Line of Defense

Adaptive (specific) defense system that mounts a specific response to pathogens, taking longer to initiate than innate defenses.

Inflammation

Nonspecific response to tissue injury that prevents pathogen spread, disposes of debris, and alerts the adaptive immune system.

Phagocytes

White blood cells that ingest and digest foreign cells and debris to protect the body from infection.

Neutrophils

Most abundant type of phagocytes that actively engulf infectious material in tissues.

Macrophages

Most active phagocytes; derived from monocytes, they can wander through tissue spaces and are essential for immune defense.

Cytokines

Chemical messengers that influence immune cell development, differentiation, and responses within the immune system.

Antigen

Any substance that triggers an immune response, often not normally found in the body, leading to antibody production.

Antibody

Proteins secreted by plasma cells that bind to specific antigens to inactivate them and mark them for destruction.

Clonal Selection

Process where a B cell is activated upon binding its specific antigen, leading to proliferation and differentiation into plasma cells.

Memory Cells

Long-lived B or T cells that remain in the body to provide long-term immunity against previously encountered antigens.

Major Histocompatibility Complex (MHC)

Proteins on the cell surface that present antigens to T cells, essential for T cell activation.

Helper T Cells

Subtype of T cells that activate B cells and other T cells to initiate the immune response.

Cytotoxic T Cells

Subgroup of T cells that directly attack and kill infected or cancerous body cells.

Passive Immunity

Immunity acquired through direct transfer of antibodies, such as from mother to fetus.

Active Immunity

Immunity developed in response to exposure to antigens, leading to the production of antibodies.

Complement System

Group of proteins that enhances immune responses, aiding in pathogen lysis and inflammation.

Interferons

Proteins produced by virus-infected cells that interfere with viral replication in neighboring cells.

Phagocytosis

Process by which phagocytes engulf and digest foreign particles and pathogens.

Opsonization

Coating of pathogens with proteins (opsonins) to enhance phagocytosis.

Natural Killer Cells

Lymphocytes that kill tumor cells and virus-infected cells without the need for prior sensitization.

Fever

Systemic response to infection that raises body temperature to enhance the immune response.

Immune System

System that provides resistance against disease-causing microorganisms such as bacteria, fungi, and viruses.

First Line of Defense

Surface barriers that include intact skin and mucosae designed to keep pathogens out.

Second Line of Defense

Innate internal defenses that respond to pathogens when the first line is breached, relying on mechanisms such as inflammation and phagocytes.

Third Line of Defense

Adaptive (specific) defense system that mounts a specific response to pathogens, taking longer to initiate than innate defenses.

Inflammation

Nonspecific response to tissue injury that prevents pathogen spread, disposes of debris, and alerts the adaptive immune system.

Phagocytes

White blood cells that ingest and digest foreign cells and debris to protect the body from infection.

Neutrophils

Most abundant type of phagocytes that actively engulf infectious material in tissues.

Macrophages

Most active phagocytes; derived from monocytes, they can wander through tissue spaces and are essential for immune defense.

Cytokines

Chemical messengers that influence immune cell development, differentiation, and responses within the immune system.

Antigen

Any substance that triggers an immune response, often not normally found in the body, leading to antibody production.

Antibody

Proteins secreted by plasma cells that bind to specific antigens to inactivate them and mark them for destruction.

Clonal Selection

Process where a B cell is activated upon binding its specific antigen, leading to proliferation and differentiation into plasma cells.

Memory Cells

Long-lived B or T cells that remain in the body to provide long-term immunity against previously encountered antigens.

Major Histocompatibility Complex (MHC)

Proteins on the cell surface that present antigens to T cells, essential for T cell activation.

Helper T Cells

Subtype of T cells that activate B cells and other T cells to initiate the immune response.

Cytotoxic T Cells

Subgroup of T cells that directly attack and kill infected or cancerous body cells.

Passive Immunity

Immunity acquired through direct transfer of antibodies, such as from mother to fetus.

Active Immunity

Immunity developed in response to exposure to antigens, leading to the production of antibodies.

Complement System

Group of proteins that enhances immune responses, aiding in pathogen lysis and inflammation.

Interferons

Proteins produced by virus-infected cells that interfere with viral replication in neighboring cells.

Phagocytosis

Process by which phagocytes engulf and digest foreign particles and pathogens.

Opsonization

Coating of pathogens with proteins (opsonins) to enhance phagocytosis.

Natural Killer Cells

Lymphocytes that kill tumor cells and virus-infected cells without the need for prior sensitization.

Fever

Systemic response to infection that raises body temperature to enhance the immune response.

Lymphocytes

A type of white blood cell that includes T cells, B cells, and Natural Killer (NK) cells, essential for adaptive immunity.

B Cells (B Lymphocytes)

Lymphocytes responsible for humoral immunity, producing antibodies upon activation.

T Cells (T Lymphocytes)

Lymphocytes responsible for cell-mediated immunity, directly attacking infected cells or regulating immune responses.

Antigen-Presenting Cells (APCs)

Immune cells (e.g., dendritic cells, macrophages, B cells) that present antigens to T cells, initiating adaptive immune responses.

Humoral Immunity

Immunity mediated by B cells and antibodies circulating in body fluids; targets extracellular pathogens.