Immune System Defense Mechanisms

Study Notes

Immune System: A Two-Part Defense

The immune system comprises two main defense mechanisms: the innate immune response and the adaptive immune response.

Innate Immune Response: The First Line of Defense

The innate immune response is immediate and does not require activation.
It consists of physical barriers, chemical barriers, complement system, and inflammation.

Physical Barriers

Skin and mucous membranes act as the first line of defense against pathogens.

Chemical Barriers

Saliva, bodily secretions, and sweat contain lysozyme, an enzyme that breaks down bacterial cell walls.
Stomach acid also contributes to chemical defense.

Complement System

The complement system is a group of chemicals circulating in blood.
These chemicals are triggered by pathogens or other white blood cells and form a membrane attack complex.
This complex punches holes in the cell membranes of pathogens, disrupting their integrity.

Inflammation

Inflammation is characterized by redness, heat, swelling, and pain.
These symptoms are caused by increased blood flow to the affected area, leading to more leaky blood vessels.
This increased blood flow delivers leukocytes (white blood cells) to fight the infection.

Leukocytes in Innate Immunity

Neutrophils: Granulocytes that secrete chemicals like bleach and peroxide, the most common type of white blood cell in the blood.
Basophils: Granulocytes that stain purple and release histamine. Closely related to mast cells found in mucous membranes.
Eosinophils: Granulocytes that stain pink and are important in fighting parasitic worms. Also elevated in allergic responses.
Macrophages: Big eaters that engulf pathogens through phagocytosis.
Dendritic cells: Similar to macrophages, both are antigen-presenting cells (APCs) that initiate the adaptive immune response.

Adaptive Immune Response: Specific and Memory-Based

The adaptive immune response requires activation and targets specific pathogens.
It involves lymphocytes, primarily T cells and B cells.
It creates memory cells to protect against future exposure to the same pathogen.

Activation of Adaptive Immunity

Helper T cells (T_H cells) are activated by APCs (macrophages and dendritic cells) presenting antigens.
Activated T_H cells stimulate cytotoxic T cells (T_C cells) and B cells.

T Cells

Cytotoxic T cells (T_C cells) directly attack and destroy pathogens.
Helper T cells (T_H cells) regulate and activate other immune cells.
Suppressor T cells fine-tune and regulate the immune response.

B Cells

When activated, B cells transform into plasma cells producing antibodies.
Antibodies bind to pathogens, neutralizing their effects and promoting phagocytosis by macrophages.
Memory B cells persist after the infection is cleared, providing long-term immunity.

Lymphocyte Circulation

Lymphocytes circulate through the bloodstream and enter tissues as needed.
They drain from tissues into lymphatic vessels, which contain lymph fluid.
Lymphocytes pass through lymph organs like tonsils, appendix, thymus, and lymph nodes, where they reside and patrol.

Hematopoiesis: The Origin of Leukocytes

All leukocytes, including lymphocytes, originate from the bone marrow.
Lymphocytes undergo final maturation in lymph organs through a process called hematopoiesis.

Summary

The innate immune response provides immediate, non-specific defense, while the adaptive immune response is specific, requires activation, and generates memory cells.
Both responses involve various leukocytes that circulate throughout the body, patrolling for pathogens.

Description

Explore the two main defense mechanisms of the immune system: the innate and adaptive immune responses. This quiz covers their components, including physical and chemical barriers, as well as the complement system. Test your knowledge of how our body protects itself from pathogens.

Immune System Defense Mechanisms

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Questions and Answers

What is the primary function of cytotoxic T cells (TC cells)?

Which cells are responsible for the production of antibodies?

Where do lymphocytes undergo their final maturation?

What is the role of memory B cells after an infection is cleared?

Which statement accurately describes the difference between innate and adaptive immune responses?

What is the primary function of physical barriers in the innate immune response?

Which of the following is NOT part of the innate immune response?

What role does the complement system play in the immune response?

What is a key characteristic of the adaptive immune response compared to the innate immune response?

Which type of white blood cell is primarily involved in phagocytosis?

Which of the following cells is responsible for presenting antigens to activate T cells?

What is the function of histamine released by basophils in the immune response?

Which of the following accurately describes the role of memory cells in the adaptive immune response?