day 2 lymphocyte

Immune System Overview

  • Infection Response

    • Involves the activity of monocytes, a type of white blood cell.

    • Monocytes identify and respond to foreign bodies.

    • Monocytes are the largest type of white blood cell.

Fever Response

  • Fever is a common response during infections (viral or bacterial).

  • Fever serves as an immune enhancement mechanism.

    • Stimulates lymphocytes to proliferate and produce Interleukin-1 (IL-1).

    • IL-1 raises the body's thermoregulatory set point.

    • This is a form of negative feedback whereby the body adjusts its normal temperature upward to combat infection.

  • IL-1 is also referred to as an endogenous pyrogen (fire maker from within).

  • Effects of elevated body temperature:

    • Inhibits microbial growth.

    • Causes liver and spleen to sequester more iron, making it unavailable for bacterial use.

    • Enhances phagocytic activity of neutrophils and monocytes.

Lines of Defense in the Immune System

  • The immune system has three lines of defense:

    1. First Line: Mechanical barriers (e.g., skin).

    • Acts as the first point of contact with pathogens.

    1. Second Line: Innate (nonspecific) defenses:

    • Chemical barriers

    • Natural Killer (NK) cells

    • Phagocytosis

    • Fever

    1. Third Line: Adaptive defenses:

    • Resistance against specific pathogens, toxins, or metabolic byproducts.

    • Relies on the ability to distinguish between the body's self and non-self via antigens.

Antigens and Immune Response

  • Definition of Antigens: Non-self molecules that evoke an immune response, characterized by their ability to trigger immune cell activation.

  • Antibodies play a role in the immune response alongside antigens.

  • Two types of immune responses:

    • Cellular immune response: Carried out by T-lymphocytes.

    • Humoral immune response: Involves antibodies produced by B-lymphocytes.

Lymphocyte Origins

  • T-lymphocytes (70-80% of circulating lymphocytes):

    • Originate in red bone marrow, migrate to the thymus for maturation.

    • Found mainly in lymphatic organs such as lymph nodes, spleen, and thoracic duct.

  • B-lymphocytes (20-30%):

    • Mature in the bone marrow and are abundant in lymph nodes, spleen, and intestinal lining.

Types of T-lymphocytes and Their Functions

  • Helper T-cells: Activate B-cells and cytotoxic T-cells by secreting cytokines.

  • Cytotoxic T-cells: Attack virally infected cells and cancer cells.

  • Memory T-cells: Provide long-term immunity by remembering pathogens.

  • Regulatory T-cells: Suppress immune responses post-infection to prevent autoimmune diseases.

Autoimmunity

  • Autoimmunity: Occurs when the immune system fails to distinguish between self and non-self, leading to the production of autoantibodies that attack the body's own cells.

    • Example: Multiple Sclerosis - immune system attacks the myelin sheaths in the CNS.

  • Other examples of autoimmune disorders:

    • Graves' Disease:

      • Symptoms: Restlessness, weight loss, increased heart rate, etc.

    • Rheumatoid Arthritis

    • Ulcerative Colitis

Types of Immunity

  • Naturally Acquired Immunity:

    • Developed after recovering from diseases or transferred from mother to infant.

  • Artificially Acquired Immunity:

    • Gained via vaccinations (injecting antigens into the body).

  • Passive Immunity: Temporary immunity acquired through external antibodies.

  • Active Immunity: Permanent immunity developed after contact with antigens, with the formation of memory B-cells.

Cardiovascular Overview

  • Blood Vessels: Main types include arteries, veins, and capillaries.

    • Arteries: Carry blood away from the heart (oxygen-rich).

    • Veins: Transport blood toward the heart (oxygen-poor).

    • Capillaries: Sites for nutrient, gas, and waste exchange.

Heart Structure and Function

  • Layers of Pericardium:

    • Fibrous Layer: Outermost.

    • Parietal Layer: Middle.

    • Visceral Layer: Innermost.

  • Middle Layer of Heart: Myocardium, composed of cardiac muscle tissue.

  • Blood Flow: Key structures include valves (mitral, tricuspid, pulmonary, aortic) that regulate blood flow through the heart.

  • Systole: Contraction phase of heart chambers.

  • Diastole: Relaxation phase of heart chambers.

Cardiac Output and Blood Pressure

  • Cardiac Output (CO): Measurement of blood volume pumped by the heart per minute (ml/min).

    • Formula: CO=StrokeVolume(SV)imesHeartRate(HR)CO = Stroke Volume (SV) imes Heart Rate (HR)

    • Stroke Volume: Volume of blood pumped with each heartbeat.

    • Heart Rate: Number of beats per minute.

Additional Points for Review

  • Understand the distinction between arteries, veins, and capillaries regarding their functions in the circulatory system.

  • Knowledge of lymph node functions relative to filtering lymph and immune surveillance.

  • Important hormones and signals involved in lymphocyte maturation, like thymosins produced in the thymus.

  • Be prepared to label heart diagrams, lymphatic structures, and recognize the importance of different types of cells involved in immune and blood processes.