Immune System: Nonspecific Defense Mechanisms

• Immune system defends against disease using nonspecific and specific mechanisms.

Nonspecific Defense Mechanisms

• Act as the body's first line of defense, providing general protection against any invader, not specific microorganisms.
• Include physical barriers like skin and mucous membranes, and chemical defenses such as lysozyme and stomach acid.

First Line of Defense

• Physical and chemical barriers prevent pathogen entry.
• Skin acts as a widespread physical barrier; broken skin allows microbe entry.
• Tears contain lysozyme to break down bacterial cell walls.
• Stomach secretions create an acidic environment to destroy pathogens.

Second Line of Defense

• Activates when pathogens breach the first line.
• It involves inflammatory response and phagocytes.

Inflammatory Response

• A reaction to tissue damage from injury or infection.
• Causes redness, swelling, and inflammation.
• White blood cells release chemical signals, causing blood vessel dilation and swelling.

Phagocytes

• Immune cells engulf and destroy bacteria and damaged cells.
• Neutrophils and macrophages are types of phagocytes.
• They recognize, surround, and digest pathogens.

Specific Defense Mechanisms

• Targeted responses to particular pathogens.
• Recognition occurs through cell surface proteins differentiating "self" from "non-self."
• Immune signaling coordinates the immune response using chemical messengers.
• B-cell activation leads to antibody production.
• T-cell activation results in direct attacks on infected cells.

Recognition and Response

• Immune cells recognize foreign cells via surface proteins, marking them as "non-self."
• Immune signaling identifies pathogens as "foreign" and responds with chemical signals.
• B-cells recognize and "remember" pathogens from previous infections.
• The immune system "remembers" for specific immunity.

Immune System Components

• Phagocytes engulf and destroy bacteria and damaged cells.
• Fever raises body temperature to slow or halt pathogen growth and speed up immune response.
• Specific antibodies recognize non-self cells through surface proteins.
• Immune signaling recognizes pathogens as "foreign".
• Previous exposure triggers specific immune responses.
• Immune cells (antibodies or specialized cells) directly attack pathogens or produce cells to destroy them.

Fighting Infections

• B lymphocytes (B cells) and T lymphocytes (T cells) are the main working cells.
• B and T cells are made in bone marrow and recognize and respond to specific antigens.
• Other components include macrophages, memory B cells, plasma cells, antibodies, cytotoxic T-cells, and memory T-cells.

Specific Immune Response

• Humoral immunity depends on antibodies produced by white blood cells circulating in blood and lymph.
• Cell-mediated immunity defends against viruses, fungi, and bacteria by destroying body cells containing antigens.

Immune System Disorders

• Can occur when the immune system overreacts to harmless antigens like pollen or dust mites.

Allergies

• Allergens trigger an inflammatory response causing sneezing, coughing, watery eyes, etc.
• Antihistamines relieve allergy symptoms.

Asthma

• It is an allergic reaction in the respiratory system causing airway narrowing, wheezing, and breathing difficulty.
• Inhaled medications relax airway muscles, providing relief.

Autoimmune Diseases

• The immune system attacks the body's own cells.
• Type 1 Diabetes involves the immune system attacking insulin-producing cells in the pancreas.
• Rheumatoid arthritis affects joint linings, leading to bone erosion and joint deformity.
• Lupus is a chronic disease affecting joints, skin, kidneys, blood cells, brain, heart, and lungs.

Vaccines

• Stimulate the immune system to produce an immune response to a specific disease without causing illness.
• The immune system recognizes antigens on the vaccine and develops antibodies.
• Antibodies are stored in memory cells.
• Upon virus invasion, antibodies attack quickly, preventing infection.