Body Defenses and Immunity Flashcards

A comprehensive set of vocabulary flashcards covering nonspecific and specific body defenses, inflammation, lymphocytes, and antibody functions based on the lecture transcript.

Nonspecific (innate) defense system

A defense system that responds immediately to protect the body from foreign substances, including external body membranes like skin and mucosa, and internal defenses like inflammation and phagocytes.

Specific (adaptive) defense system

Also known as the Immune System, it mounts attacks against specific foreign substances using macrophages and lymphocytes.

Immunity

Resistance to disease.

Keratin

A protein in the epidermis that serves as a physical barrier resistant to weak acids, bases, bacterial enzymes, and toxins.

Acid mantle

Acidic skin secretions that prevent bacterial growth.

Lysozyme

An antibacterial enzyme found in saliva and lacrimal fluid (tears).

Phagocytes

Cells, mainly macrophages originating from monocytes, that function by engulfing foreign bodies via phagocytosis.

Opsonization

The process of coating a foreign substance with proteins, usually complement proteins, to make adhesion by phagocytes possible.

Natural Killer (NK) cells

Non-phagocytic cells located in blood and lymph that lyse and kill cancer and virus-infected cells by releasing cytolytic enzymes called perforins.

Inflammation

A response to tissue injury that prevents the spread of damaging agents, disposes of debris, and sets the stage for repair; characterized by redness, heat, swelling, and pain.

Vasodilation

The dilation of local arterioles during inflammation that increases blood flow, resulting in heat and redness.

Edema

Local swelling caused by increased permeability of local capillaries, allowing fluid to enter interstitial spaces.

Leukocytosis-inducing factors

Chemicals released by injured cells that promote the rapid release of neutrophils from the red bone marrow.

Margination

The process where neutrophils stick to the endothelial wall by attaching to cell adhesion molecules (CAMs) called selectins.

Diapedesis

The process by which neutrophils squeeze through capillary walls to reach damaged tissue.

Positive chemotaxis

The movement of neutrophils following a chemical trail left by injured cells or other white blood cells to a damaged area.

Complement proteins

A group of at least $20$ plasma proteins that, when activated, amplify inflammation, lyse bacteria, and enhance phagocytosis through opsonization.

Interferons

Proteins released by virus-infected cells that stimulate uninfected cells to produce PKR, a protein that inhibits viral replication.

Pyrogen

A chemical released by leukocytes and macrophages that raises the body’s thermostat, causing a fever.

Humoral immunity

Also known as antibody-mediated immunity, it involves antibodies produced by B lymphocytes circulating in blood and lymph.

Cellular immunity

Also known as cell-mediated immunity, it involves T-lymphocytes that act directly by lysing cells or indirectly by releasing chemicals.

Antigens

Non-self (foreign) substances that provoke an immune response and mobilize the immune system.

Complete antigens

Substances that are both immunogenic (stimulate lymphocyte proliferation) and reactive (react with those lymphocytes or antibodies).

Haptens

Incomplete antigens that are not immunogenic on their own but can become immunogenic when combined with body proteins.

Antigenic determinants

The specific parts of an antigen that are immunogenic and serve as binding sites for antibodies or lymphocytes.

MHC (major histocompatibility complex) proteins

A group of glycoproteins that mark a cell as self; Class 1 are on all body cells, while Class 2 are only on certain immune cells (APCs).

Immunocompetent

The ability of a lymphocyte to recognize a specific antigen by binding to it.

Self-tolerant

The characteristic of a lymphocyte being unresponsive to the body's own (self) antigens.

Antigen-Presenting cells (APCs)

Cells such as macrophages, dendritic cells, and B-cells that engulf and digest antigens to present fragments on their surface near MHC proteins.

Clonal selection

The process where the activation of a B cell triggers it to grow and multiply into a family of identical cells called a clone.

Plasma cells

Antibody-producing cells resulting from B cell clones that typically last $4$ to $5$ days.

Primary immune response

The immune response occurring on the first exposure to an antigen, characterized by a lag period of $3$ to $6$ days and peak antibody levels at $10$ days.

Secondary immune response

A faster and more effective response upon re-exposure to an antigen, with peak antibody levels reached in $2$ to $3$ days.

Naturally acquired active immunity

Long-term immunity resulting from a person getting sick after exposure to a pathogen and producing memory cells.

Artificially acquired active immunity

Long-term immunity produced after receiving a vaccine (dead or weakened strain) without typically becoming ill.

Naturally acquired passive immunity

Short-term immunity provided by antibodies passed from a mother to a fetus via the placenta or to a child via breast milk.

IgG

The most abundant and diverse antibody in plasma ($75$ to $85$%); it crosses the placenta and is the main antibody of the secondary immune response.

IgA

An antibody found in exocrine secretions like milk, tears, and sweat that helps prevent pathogen attachment to epithelial surfaces.

Precipitation

An antigen-antibody reaction where soluble molecules are cross-linked into large complexes, making them easier to capture.

Agglutination

The clumping of foreign cells or substances due to an antigen-antibody reaction.

Neutralization

The process where antibodies block specific sites on viruses or bacterial toxins so they lose their toxic effects.

Helper T (TH) cells

CD4 cells that act as managers of the immune response by activating macrophages and inducing B and T cell proliferation.

Cytotoxic T (Tc) cells

CD8 cells that directly attack and kill other cells using perforins and granzymes.

Regulatory T (TReg) Cells

Cells that slow or stop the activity of B and T cells once an infection has been conquered.

Cytokines

Proteins like interleukins that influence cell development and immune responses, mainly produced by lymphocytes and monocytes.

Autoimmune disease

A condition where the immune system attacks the body's own tissues, such as in lupus or Multiple Sclerosis.