Blood Components & Immune System

• Blood, a vital fluid, totals about 5 liters in a 70 kg adult.
• It consists of plasma, erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (thrombocytes).
• Blood functions in transport (oxygen, nutrients), clotting, and immune defense.
• Blood originates from stem cells in bone marrow.

Role of the Immune System

• The immune system defends the body against pathogens and maintains homeostasis.
• It involves cellular (T cells, B cells) and non-cellular components (skin, antibodies).
• Immune cells include macrophages, helper T cells, killer T cells, suppressor T cells, and memory T cells.
• Immune system effectiveness depends on genetics, environment, and health.
• Understanding the immune system is key to developing vaccines and treatments for infectious diseases.

Components of Blood

Plasma

• Plasma is about 55% of blood volume, composed of 90% water and 10% dissolved substances.
• Plasma contains albumins (maintain osmotic pressure), globulins (immunity), and fibrinogen (clotting).
• Plasma proteins regulate fluid balance and immune responses.
• Plasma composition varies with physiological conditions like dehydration or infection.

Erythrocytes (Red Blood Cells)

• Erythrocytes make up about 45% of blood volume and transport oxygen.
• They contain hemoglobin, a protein that binds oxygen.
• The biconcave shape increases surface area for gas exchange and flexibility.
• Anemia and sickle cell disease affect oxygen-carrying capacity.

Leukocytes (White Blood Cells)

• Leukocytes are less than 1% of blood volume and defend against pathogens.
• Different types of WBCs include neutrophils, lymphocytes, and monocytes.
• WBC counts increase during infections, indicating an active immune response.

Platelets (Thrombocytes)

• Platelets are cell fragments involved in blood clotting and wound healing.
• They release thromboplastin, initiating the clotting cascade.
• Fibrinogen converts to fibrin, forming a mesh to seal wounds.
• Thrombocytopenia can cause bleeding or clotting issues.

Blood Types and Transfusion Safety

Discovery of Blood Types

• Karl Landsteiner's 1901 discovery of blood types made transfusions safer.
• Incompatible blood can cause agglutination, which can be fatal.
• Landsteiner won the 1930 Nobel Prize in Physiology or Medicine for his work.

Blood Group Antigens and Antibodies

• Blood types are determined by antigens on red blood cells and antibodies in plasma.
• Antigens 'name tag' blood cells, while antibodies attack foreign antigens.
• The ABO and Rh blood group systems are clinically significant.

Implications of Blood Type Compatibility

• Mismatched transfusions cause severe immune reactions.
• Type O blood is the universal donor, while type AB is the universal recipient.
• Blood type testing is routine before surgeries and transfusions.

Blood Types Overview

Different Blood Types

• Four primary blood types: A, B, AB, and O.
• Blood Group A: A Antigens, B antibodies
• Blood Group B: B Antigens, A antibodies
• Blood Group AB: A and B Antigens, no antibodies (universal recipient)
• Blood Group O: no antigens, A and B antibodies (universal donor)

Blood Donation Compatibility

• Blood donation requires antigen compatibility to avoid immune reactions.
• Wrong blood types cause antibody attacks, leading to agglutination.
• Type O blood lacks A and B antigens, preventing agglutination in recipients of any blood type.
• Type AB blood is the universal recipient, accepting blood from any type.

Rh Factor and Its Implications

Understanding the Rh Factor

• The Rh factor is an antigen classified as Rh+ (present) or Rh- (absent).
• Rh+ individuals lack Rh antibodies, while Rh- individuals can develop them if exposed to Rh+ blood.

Erythroblastosis Fetalis

• Presence of Rh antibodies can complicate transfusions and pregnancies.
• Erythroblastosis fetalis occurs when an Rh- mother with anti-Rh antibodies carries an Rh+ fetus.
• Anti-Rh antibodies cross the placenta, leading to hemolysis of fetal RBCs.
• Risk increases with subsequent pregnancies with Rh+ children.
• A solution is transfusing the baby with Rh- blood.

Blood and Immunity Practice Problems

Key Concepts in Blood and Immunity

• Erythrocytes transport oxygen throughout the body.
• Hemoglobin deficiency results from iron deficiency anemia or hemorrhage.
• Leukocytes have nuclei and mediate immune responses, unlike RBCs.
• Leukocytes destroy pathogens and produce antibodies.
• Platelets form plugs at injury sites and promote clotting.

Additional Blood and Immunity Concepts

Pathogens and the Immune Response

• A pathogen causes disease (bacteria, viruses, fungi, and parasites).
• The immune system has physical barriers, innate responses, and adaptive immunity.
• Immune response effectiveness depends on age, nutrition, and health.
• Vaccination prepares the immune system to combat specific pathogens.

Overview of Pathogens and the Immune System

Definition of Pathogens

• Pathogens cause diseases and include viruses, bacteria, fungi, protozoa, and helminths.

• Examples:

  • Malaria: Plasmodium protozoan parasites
  • HIV (AIDS): Virus attacking the immune system
  • Influenza (Flu): Viral infection of the respiratory system
  • Tapeworms: Parasitic flatworms
  • Giardia: Protozoan from contaminated water

The Immune System: An Overview

• Three lines of defense:
  • Physical barriers (skin, mucous membranes)
  • Non-specific internal responses (phagocytes, inflammatory response)
  • Specific immune response (B cells and T cells)

The Three Lines of Defence

First Line of Defence: Physical Barriers

• Skin: Barrier against pathogens
• Mucous Membranes: Trap pathogens in the respiratory tract
• Coughing and Sneezing: Eject foreign particles
• Hydrochloric Acid: Kills ingested pathogens in the stomach
• Lysozyme Enzyme: Destroys bacterial cell walls in tears and saliva

Second Line of Defence: Non-Specific Immune Response

• Phagocytosis: Macrophages engulf and digest pathogens
• Inflammatory Response: Increased blood flow, swelling, redness, heat, and pain
• Fever: Elevated body temperature inhibits bacterial survival
• Pus Formation: Dead WBCs and debris indicate an active immune response

Third Line of Defence: Specific Immune Response

• Lymphocytes (B cells and T cells) respond to antigens.
• Macrophages: Present antigens to Helper T cells.
• B Cells: Produce antibodies to clump pathogens.
• Killer T cells: Destroy infected cells.
• Memory Cells: Enable faster response upon re-exposure.

Immune Response Mechanism

Steps of the Immune Response

• Pathogen Entry: Pathogen enters the body and displays antigens.
• Macrophage Action: Macrophages engulf the pathogen and present antigens to Helper T cells.
• Helper T Cell Activation: Helper T cells replicate and signal B cells and Killer T cells.
• B Cell Response: B cells produce specific antibodies.
• Antibody Action: Antibodies bind and clump pathogens.
• Killer T Cell Action: Killer T cells destroy infected cells.
• Suppressor T Cells: Regulate immune response.
• Memory Cells: Enable rapid response to future infections.

Vaccination and Immunity

• Vaccines introduce antigens to stimulate antibody and memory cell production.
• Edward Jenner developed the first vaccine in 1800 (cowpox for smallpox).
• mRNA Vaccines: Instruct cells to produce harmless pathogen pieces for immune response.

Practice Problems and Key Concepts

Key Questions on Immune Function

• How does lysozyme protect?: It destroys bacterial cell walls.
• Protective mechanisms of the respiratory tract: Mucus traps, and cilia sweep pathogens out.
• Signs of immune function: Swelling and pus indicate inflammation and phagocytosis.
• Roles of B cells, Helper T cells, and Killer T cells: They eliminate pathogens.

Summary of Immune System Functions

• The immune system protects against pathogens.
• It uses multi-layered defenses from physical barriers to cellular responses.
• Understanding the immune response is crucial for developing effective vaccines and treatments.

Overview of the Immune System

Components of Pus and Immune Response

• Pus is composed of protein fragments, dead white blood cells, and digested microbes, indicating active phagocytosis.
• Pus signifies the immune system is responding to an infection.
• Phagocytosis is the process where immune cells engulf and digest pathogens, playing a crucial role in innate immunity.
• Understanding pus can help in diagnosing infections and determining the appropriate treatment.

Key Immune Cells and Their Functions

• B cells, helper T cells, and killer T cells are essential lymphocytes in the adaptive immune response.
• Helper T cells identify invaders through antigen markers and communicate with B cells via lymphokines to enhance the immune response.
• Killer T cells directly attack and destroy infected host cells, preventing the spread of viruses.
• The collaboration between these cells is vital for a robust immune response against infections.
• B cells produce antibodies that bind to antigens, neutralizing pathogens and forming memory cells for future immunity.

Mechanisms of Antibody Action

How Antibodies Defeat Antigens

• Antibodies are specific proteins that bind to antigens, forming larger complexes that enhance visibility to leukocytes.
• The binding of antibodies can neutralize toxins and prevent pathogens from entering host cells.
• Antibodies play a critical role in opsonization, marking pathogens for phagocytosis by immune cells.
• The four main contributions of antibodies include: binding to bacteria, neutralizing toxins, recognizing diverse antigens, and blocking viral entry.
• Understanding antibody function is crucial for vaccine development and therapeutic interventions.

Memory B Cells and Long-term Immunity

• Memory B cells retain information about specific antigens, allowing for rapid response upon re-exposure to the same pathogen.
• Most T and B cells die after an infection, but memory B cells persist, ensuring long-term immunity.
• The quick mobilization of antibody-producing B cells by memory cells is essential for preventing reinfection.
• Memory B cells are a key component of the adaptive immune system, providing a basis for vaccination strategies.
• The longevity of memory B cells is critical for effective immunological memory.

Malfunctions of the Immune System

Types of Immune System Malfunctions

• Immune system malfunctions can lead to allergies, autoimmune diseases, immunodeficiency diseases, and organ transplant rejection.
• Allergies occur when the immune system mistakenly identifies harmless antigens as threats, leading to overreactions.
• Autoimmune diseases arise when the immune system attacks the body's own cells, often due to mutated T and B cells.
• Immunodeficiency diseases, such as SCID and HIV, result in a weakened immune response, making individuals susceptible to infections.
• Organ transplant rejection occurs when the recipient's immune system attacks the foreign antigens of the donor organ.

Allergies and Their Mechanisms

• Allergies are caused by the immune system's overreaction to harmless substances, such as food or pollen.
• Histamines released by basophils and mast cells increase capillary permeability, leading to allergy symptoms like swelling and itching.
• Severe allergic reactions can result in anaphylaxis, which is life-threatening and requires immediate medical attention.
• Treatments include antihistamines and corticosteroids to reduce inflammation and manage symptoms.
• Understanding allergies is important for developing effective prevention and treatment strategies.

Specific Conditions Related to Immune Malfunctions

Autoimmune Diseases

• Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues, often due to mutated immune cells.
• Examples include rheumatoid arthritis, multiple sclerosis, type 1 diabetes, and lupus, each affecting different body systems.
• The role of suppressor T cells is crucial in preventing autoimmune attacks; their failure can lead to disease.
• Research into autoimmune diseases focuses on understanding triggers and developing targeted therapies.
• Awareness of autoimmune conditions is essential for early diagnosis and management.

Immunodeficiency Disorders

• Immunodeficiency disorders, such as SCID and HIV, result in a compromised immune system, increasing infection risk.
• SCID is characterized by the absence of functional T and B cells, leading to severe vulnerability to infections.
• HIV targets helper T cells, impairing the immune response and potentially leading to AIDS if untreated.
• Historical cases, such as David, the 'boy in the bubble,' highlight the severe consequences of immunodeficiency.
• Advances in medical treatments have improved outcomes for individuals with immunodeficiency disorders.

Organ Transplant Rejection

• Organ transplant rejection occurs when the recipient's immune system recognizes the donor organ as foreign and attacks it.
• Matching donor organs to recipients is critical to minimize rejection risk and improve transplant success rates.
• Immunosuppressant drugs are used to reduce the immune response, but they increase the risk of infections.
• Understanding the mechanisms of transplant rejection is vital for improving transplant outcomes and patient care.
• Ongoing research aims to develop better immunosuppressive therapies and improve organ compatibility.

Blood Components and Functions

Red Blood Cells (RBCs)

• RBCs are biconcave, disc-shaped cells that lack a nucleus, allowing for increased surface area for gas exchange.
• The absence of a nucleus in RBCs maximizes space for hemoglobin, which is crucial for oxygen transport.
• Their biconcave shape enhances flexibility, enabling them to navigate through narrow capillaries.
• In a normal blood smear, RBCs are abundant, typically outnumbering WBCs by a ratio of about 600:1.

White Blood Cells (WBCs)

• WBCs are crucial for the immune response, with various types serving different functions.
• The three major types of WBCs include: Macrophages, T Cells, and B Cells.
• Macrophages are the first responders to foreign invaders, engulfing pathogens through phagocytosis.
• T Cells can be further categorized into Helper T Cells, Killer T Cells, and Suppressor T Cells, each playing a unique role in immune defense.

Blood Smear Analysis

• Blood smears can reveal important health information based on the appearance of blood cells.
• In cases of anemia, blood smears show fewer RBCs that appear paler with larger centers, indicating reduced oxygen-carrying capacity.
• Sickle-cell anemia is characterized by crescent-shaped RBCs, leading to complications like pain and poor circulation.

Immune System Overview

Immune Response Mechanisms

• The immune system employs various cells to identify and eliminate pathogens.
• Helper T Cells identify invaders by recognizing antigens and coordinate the immune response by signaling B Cells to produce antibodies.
• Killer T Cells directly attack and destroy infected cells by puncturing their membranes.

Antibody Functionality

• Antibodies play a critical role in neutralizing pathogens.
• They bind to antigens, forming antigen-antibody complexes that enhance visibility to leukocytes, facilitating pathogen elimination.
• This process is essential for the effectiveness of vaccines and immune memory.

Allergic Reactions and Autoimmune Disorders

• Allergic reactions occur when the immune system overreacts to harmless substances, such as peanut proteins.
• Severe allergic reactions can lead to anaphylaxis, characterized by airway swelling and a drop in blood pressure.
• Autoimmune disorders arise when the immune system mistakenly attacks the body's own cells, leading to various health issues.

Clinical Implications and Health Assessments

Blood Tests and Indicators of Infection

• Blood tests, such as white blood cell counts, are vital for diagnosing infections.
• An elevated WBC count typically indicates that the body is actively fighting an infection, as more leukocytes are produced.
• Physicians may request these tests when patients present with symptoms like high fever.