Lymphatic and Immune Systems PDF

[Lymphatic and immune system] ----------------------------------------- - These two systems, although it would be more accurate to call it one system, are composed of: - - - - - There are three major roles that lymphatic and immune system perform: 1. ***Drainage of excess inter...

[Lymphatic and immune system] ----------------------------------------- - These two systems, although it would be more accurate to call it one system, are composed of: - - - - - There are three major roles that lymphatic and immune system perform: 1. ***Drainage of excess interstitial fluid*** 2. ***Transportation of dietary lipids*** 3. ***Immune response*** *Lymphatic vessels are absent in: CNS, cartilage, epidermis, bone marrow.* Schematic approach to lymphatic system ====================================== **Lymphatic capillaries Lymphatic vessels Lymph nodes** Intertwine between other In limbs they run parallel Scattered capillaries. Thin walled to veins, and in body cavities throughout the body with overlapping lymphatic vessels are closer Approximately 600 endothelial cells that create. to arteries. lymph nodes are valvular mechanism. found within human body - **Lacteals** -- they are specialized lymphatic vessels of the small intestine that help absorption of dietary lipids. - **Lymphatic trunks** -- they are larger lymphatic vessels such as lumbar, intestinal, broncho-mediastinal, subclavian or jugular trunks. Merger of lymphatic trunks gives rise to major two lymphatic vessels: 1. **The thoracic duct** -- This is the largest lymphatic vessel. It originates at L2 vertebra with enlargement that is called **cysterna chyli**. It receives the lymph from the lower half of the body (inferior to ribs) and from the left side of the head, neck, face, chest and left upper limb. It **drains into left subclavian vein.** 2. **The right lymphatic duct** -- It **drains into right subclavian vein**. It receives the lymph from the right side of the head, neck, face, right side of the chest and upper right limb. Movement of lymph is also affected by the skeletal muscle pump and the respiratory pump. [Lymphatic organs and tissues] ------------------------------------------ ***Primary lymphatic organs*** -- where stem cells divide and become immunocompetent -- red bone marrow and thymus. ***Secondary lymphatic organs*** -- where immune responses occur -- **lymph nodes, spleen and lymphatic nodules**. Lymphatic nodules are found in digestive and respiratory systems and they are called **MALT** - mucosa associated lymphatic tissue. Examples: Peyer's patches in the small intestine or pharyngeal (adenoid), lingual and palatine tonsils. IMMUNE SYSTEM ============= Nonspecific immune systems -------------------------- **Innate defenses (inborn defenses)** - Don't have any specific means of action. Use the same defensive mechanisms for any type of invaders. ### [First lines of defense] -- mechanical barriers, movement of material and chemical defense ### ### ### Mechanical defenses - Barriers 1. Epidermis 2. Mucous membranes -- mucus, hairs, cilia *Movement of material* ---------------------- 1. Lacrimal apparatus 2. Saliva 3. Flow of urine 4. Defecation and vomiting *Chemical defenses* ------------------- 1. Sebum (unsaturated fatty acids inhibit growth of certain bacteria) 2. Perspiration 3. Lyzozyme (enzyme) 4. Gastric juice 5. Vaginal secretions ### ### ### ### [Second line of defense] (internal defenses) Antimicrobial proteins ---------------------- - Interferon (protein released from infected cells -- macrophage, lymphocytes or fibroblasts); it attaches to the surface of uninfected cell; interfere with viral replication and hopefully stop it. Viruses can cause a disease only if their replication is unaffected) - Complement proteins - when activated they enhance immune, allergic and inflammatory reactions) - Transferrins (iron-binding proteins) -- they reduce the amount of available iron that must be available for growth of certain bacteria [Natural killer cells and phagocytosis] --------------------------------------------------- - Natural killer cells (lymphocytes that are different than B or T lymphocytes). - 5-10% of NK cells circulate. They attack any cell that displays abnormal or foreign plasma membrane proteins. They will kill either by: - - - Macrophage cells and neutrophils do phagocytosis -- ingestion of microorganisms or foreign particles. - Macrophage cells are enlarged monocytes; phagocytes could be wandering (migrating) and fixed (stationary within an organ). [Inflammation ] --------------------------- - Another form of non-specific immune response - It is characterized by 4 cardinal (characteristic) signs of inflammation: - - - - - - Inflammatory response has three main (basic) stages: - - - Fever ----- - Abnormally high body temperature - Commonly caused by release of Interleukin --1 by bacterial toxins - Increased body temperature helps damage and destroy microorganisms faster Specific immunity ================= Specific immune response is provoked by antigens. Antigen could be defined as any substance capable of triggering immune response. Specific immunity is generated and gained throughout the life, as we are constantly exposed to microorganisms or their fragments that we haven't encountered before. Specific immunity has: 1. Specificity for particular foreign molecules (antigens) 2. Memory for previously encountered antigens (second response is prompt and vigorous) Maturation of lymphocytes ------------------------- Lymphocytes are carriers of our specific immune response. In order to do so, they must mature and the process of their maturation occurs in bone marrow (it generates B-lymphocytes) and within the thymus (producing mature form of T-lymphocytes. During the process of maturation lymphocytes acquire distinct surface proteins that have role of antigen receptor site. - T cells exit the thymus with either CD4+ or CD8+ proteins Types of immune responses ------------------------- The specific immune response could be either **cell-mediated** response or **antibody-mediated** response, which is also known as **humoral** response. **Cell mediated immune response** - CD8+ T-cells proliferate into cytotoxic T-cells and they directly attack invading agent **Humoral (antibody mediated) response** - B-cells (B-lymphocytes) transform into plasma cells, which then synthesize and release antibodies. Antibodies are complex proteins called the immunoglobulins. - Mechanism of action is to allow antibodies to bind to a specific antigen, inactivate it, and sometimes use CD4+ T-cells (helper T-cells). [Cell mediated immune response] ------------------------------------------- 1. T-cell receptors (TCR) recognize and bind to a specific antigen 2. Co-stimulation with interleukin 1 or 2 is required to make a contact between T-cell and a cell which presents the antigen. Co-stimulation is required to prevent accidental immune response. 3. Activated cell (step 2 complete), proliferates and differentiates. Thousands of cloned cells are produced that can recognize the same antigen. Activation happens in secondary lymphatic organs 4. 3 types of T cells: a. b. c. Action of cytotoxic T cells --------------------------- - Release perforins ( fluid moves into cell and it subsequently bursts) - Secretes lymphotoxin (activate enzymes within the target cell, destroy DNA) **[Antibody mediated immunity (humoral immune response)]** When presence of foreign antigens is detected (antigens are released from destroyed cells after activation of T cells), B-lymphocytes become activated. Their activation results in their **transformation into plasma cells**. Plasma cells start producing and releasing antibodies (immunoglobulins). **Antibody actions** 1. Neutralization (antibody + antigen combination neutralizes toxins or prevents attachment of viruses to cellular bodies). 2. Immobilization of bacteria (binding of antibody to bacterial cilia or flagella of mobile bacteria, limiting their mobility) 3. Agglutination (clumping together) and precipitation 4. Activation of complement 5. Enhance phagocytosis (process called opsonization) Complement system ----------------- - Utilizes existing plasma proteins which enhance immunological reaction by increasing inflammation, enhancing phagocytosis and physical destruction of microorganisms