Immunity and Blood Cells Overview

Immunity

• The body's specific defense mechanism against foreign agents and organisms.
• It is the body's ability to resist infection, disease, or other harmful foreign substances.
• Allows rapid responses to foreign substances in a specific manner.

White Blood Cells (WBCs)

• Produced in the bone marrow.
• Involved in immunity.
• B lymphocytes (B cells) and T lymphocytes (T cells) are the two main types of WBCs involved in immunity.

Lymphocytes

• Originate from stem cells in the bone marrow.
• B lymphocytes mature in the bone marrow before entering the bloodstream.
• T lymphocytes mature in the thymus, where they differentiate into cells with various functions.

Lymph Nodes

• Connected by lymph channels and capillaries distributed throughout the body.
• Remove foreign material from the lymphatic system before it enters the bloodstream.
• Serve as centers for immune cell proliferation.

The Spleen

• Composed of red and white pulp, acting like a filter.
• Red pulp destroys old and injured red blood cells (RBCs).
• White pulp contains concentrations of lymphocytes.

Adaptive Immunity

• Acquired immunity that develops as a result of prior exposure to an antigen.
• This exposure can be through immunization (vaccination) or by contracting a disease.
• Both immunization and contracting a disease generate a protective immune response.

Immune Responses

• Phagocytic Immune Response: WBCs (granulocytes and macrophages) ingest foreign particles and destroy invading agents.
• Cellular Immune Response: Involves T lymphocytes that differentiate into cytotoxic (killer) T cells, attacking pathogens directly.
• Humoral or Antibody Immune Response: Begins with the transformation of B lymphocytes into plasma cells that manufacture antibodies.

Antibodies

• Large proteins (also called immunoglobulins).
• Mobilize other components of the immune system to defend against invaders.

T Lymphocytes

• Effector Helper T Cells: Activated by antigen recognition.
• Stimulate other immune system components.
• Secrete cytokines, which attract and activate B cells, cytotoxic T cells, NK cells, macrophages, and other immune cells.
• Effector Cytotoxic T Cells (Killer T Cells): Attack antigens directly by altering cell membranes, causing cell lysis.
• Regulatory or Suppressor T Cells: Decrease B-cell production, keeping the immune response balanced.
• Memory T Cells: Recognize antigens from previous exposures, and mount an immune response.

Cellular Response to Injury: Inflammation

• A localized reaction intended to neutralize, control, or eliminate the offending agent.
• Prepares the site for repair.
• Major function of the natural immune system.
• Elicited in response to tissue injury or invading organisms.

5 Cardinal Signs of Inflammation:

• Pain - Heat - Redness - Swelling - Loss of Function

Pathophysiology of Inflammation

• Involves changes in the microcirculation including vasodilation, increased vascular permeability, and leukocytic cellular infiltration.
• The changes in microcirculation lead to the 5 cardinal signs of inflammation.
• Vasodilation and increased blood flow to the injured area cause local warmth and redness.
• Increased vascular permeability causes plasma fluids to leak into the tissues, producing swelling (edema).
• Pain is caused by pressure of fluids or swelling on nerve endings and irritation of nerve endings by chemical mediators.
• Loss of function is often due to pain and swelling.
• Leukocytes exit the blood stream and migrate to the injury site to engulf offending organisms and remove cellular debris.
• Fibrinogen in the leaked plasma fluid coagulates, forming fibrin for clot formation, which walls off the injured area and prevents the spread of infection.

Explore the fascinating world of the immune system with this quiz on immunity, white blood cells, lymphocytes, and lymphatic structures. Test your knowledge on how the body defends itself against diseases and foreign substances. Dive into the roles of various immune cells and organs in maintaining health.