AP Bio: The Immune System - Part 1
Introduction to the Immune System
Discussion on the immune system's function and personal context of being sick during the lecture.
Types of Blood Cells
Red Blood Cells (RBCs):
Shaped like a doughnut with an incomplete hole.
White Blood Cells (WBCs):
Often phagocytic, appearing whitish.
Integral to the immune system.
Lines of Defense in the Immune System
First Line of Defense:
Physical Barrier: Skin acts as a barrier to protect interstitial fluid and blood.
Secretions: Antimicrobial proteins and mucus help capture and eliminate pathogens.
Second Line of Defense:
Non-Specific Defense Mechanisms:
Antimicrobial proteins in the blood go after general pathogens.
WBCs attack non-self cells, acting like 'bouncers' rather than specific hunters.
Types of White Blood Cells
Neutrophils:
Comprise ~70% of WBCs.
Function as infantry, responding to infection.
Pus is a result of neutrophil activity.
Macrophages:
Matured monocytes that engulf and destroy pathogens.
Serve as guards in tissues.
Eosinophils:
Target larger pathogens such as parasitic worms; tend to use enzymes more than phagocytosis.
Natural Killer Cells:
A type of lymphocyte that targets cancerous and virus-infected cells.
Inflammatory Response
Description:
Occurs in response to injury, helping to prevent pathogen entry.
Mast Cells and Histamine Release:
Mast cells release histamine, increasing blood flow to the affected area.
Results in swelling, redness, and increased temperature to inhibit bacterial growth.
Inflammatory Signs:
Swelling, redness, heat, and the presence of WBCs act as a defensive mechanism.
Specific Immunity
Activation: Occurs after nonspecific responses, aiming to target specific pathogens that have breached initial defenses.
Types of Lymphocytes:
B Cells: Mature in bone marrow; produce antibodies targeting antigens.
T Cells: Mature in thymus; involved in cell-mediated immunity.
Antigens and Antibodies
Antigens: Molecules recognized by the immune system as foreign, triggering a response.
Antibodies: Produced by B cells to neutralize or destroy specific antigens.
Antibodies are specific to pathogens; different pathogens require different antibodies.
Clonal Selection and Memory Cells
Clonal Selection:
Process where specific B or T cells are cloned to attack identified pathogens.
Memory Cells:
Long-lived cells that enhance response to subsequent infections by the same pathogen.
Result in quicker immune response and improved resistance against reinfection.
Self vs Non-Self Recognition
Importance of distinguishing between body’s own cells and foreign pathogens.
Autoimmune Diseases: Occur when the immune system incorrectly identifies self-cells as foreign (e.g., lupus, type 1 diabetes).
MHC (Major Histocompatibility Complex): Molecules that help the immune system recognize self-cells, critical in organ transplants and blood transfusions.
Conclusion
Importance of accurate immune recognition to prevent infections while avoiding autoimmunity.
Genetic relatedness plays a role in match probability for transplants.