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ما هو دور الأغشية المخاطية في الجسم?
ما هو دور الأغشية المخاطية في الجسم?
ما هو العنصر الأكثر شيوعًا في إفرازات الغشاء المخاطي?
ما هو العنصر الأكثر شيوعًا في إفرازات الغشاء المخاطي?
كيف تساهم الأغشية المخاطية في حماية الجسم?
كيف تساهم الأغشية المخاطية في حماية الجسم?
ما هو تأثير الكائنات الغازية على الأغشية المخاطية?
ما هو تأثير الكائنات الغازية على الأغشية المخاطية?
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أي من الخيارات التالية ليس وظيفة للأغشية المخاطية?
أي من الخيارات التالية ليس وظيفة للأغشية المخاطية?
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ما هي المجموعة البروتينية الفريدة التي تعبر عنها الخلايا التائية المساعدة؟
ما هي المجموعة البروتينية الفريدة التي تعبر عنها الخلايا التائية المساعدة؟
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ما معنى الـ CD في سياق الخلايا الليمفاوية؟
ما معنى الـ CD في سياق الخلايا الليمفاوية؟
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أي من الخيارات التالية تعد مجموعة فرعية من الخلايا الليمفاوية التائية؟
أي من الخيارات التالية تعد مجموعة فرعية من الخلايا الليمفاوية التائية؟
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ما هي الوظيفة الرئيسية للخلايا التائية المساعدة؟
ما هي الوظيفة الرئيسية للخلايا التائية المساعدة؟
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ما هو الدور المحدد للأجسام المضادة IgD في وظيفة المناعة؟
ما هو الدور المحدد للأجسام المضادة IgD في وظيفة المناعة؟
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كيف تختلف الخلايا التائية المساعدة عن الخلايا التائية القاتلة؟
كيف تختلف الخلايا التائية المساعدة عن الخلايا التائية القاتلة؟
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ما النسبة المئوية التي تمثلها IgD من الأجسام المضادة في الجسم؟
ما النسبة المئوية التي تمثلها IgD من الأجسام المضادة في الجسم؟
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أي من التالي يعتبر من الوظائف المحتملة للأجسام المضادة IgD؟
أي من التالي يعتبر من الوظائف المحتملة للأجسام المضادة IgD؟
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كيف يمكن وصف الأجسام المضادة IgD من حيث نسبتها في الجسم؟
كيف يمكن وصف الأجسام المضادة IgD من حيث نسبتها في الجسم؟
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ما هي الخلايا التي تتطلب وجود IgD للنضج؟
ما هي الخلايا التي تتطلب وجود IgD للنضج؟
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ما هي وظيفة السيتوكينات في الجسم؟
ما هي وظيفة السيتوكينات في الجسم؟
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كيف تؤثر الأجسام المضادة على الخلايا المستهدفة؟
كيف تؤثر الأجسام المضادة على الخلايا المستهدفة؟
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ما الدور الذي تلعبه السيتوكينات في الاستجابة المناعية؟
ما الدور الذي تلعبه السيتوكينات في الاستجابة المناعية؟
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أي من العبارات التالية تصف تدمير الخلايا المستهدفة؟
أي من العبارات التالية تصف تدمير الخلايا المستهدفة؟
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ما الذي يميز السيتوكينات عن غيرها من البروتينات؟
ما الذي يميز السيتوكينات عن غيرها من البروتينات؟
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ما هو دور الكريات البيض في استجابة الجسم للالتهاب؟
ما هو دور الكريات البيض في استجابة الجسم للالتهاب؟
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أي من التالي يعتبر أول نوع من خلايا الدم البيضاء يصل إلى مكان الإصابة؟
أي من التالي يعتبر أول نوع من خلايا الدم البيضاء يصل إلى مكان الإصابة؟
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كيف تتوجه الكريات البيض إلى المنطقة المصابة؟
كيف تتوجه الكريات البيض إلى المنطقة المصابة؟
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أي نوع من التعبيرات يمكن أن يترافق مع استجابة الجسم للالتهاب؟
أي نوع من التعبيرات يمكن أن يترافق مع استجابة الجسم للالتهاب؟
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ما الغرض من استجابة الخلايا المناعية في موقع الإصابة؟
ما الغرض من استجابة الخلايا المناعية في موقع الإصابة؟
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ما هو الدور الرئيسي للخلايا الليمفاوية البائية؟
ما هو الدور الرئيسي للخلايا الليمفاوية البائية؟
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كيف تؤثر السيتوكينات على الخلايا الليمفاوية البائية؟
كيف تؤثر السيتوكينات على الخلايا الليمفاوية البائية؟
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ما هي الآلية التي تعتمد عليها فورين لعملها؟
ما هي الآلية التي تعتمد عليها فورين لعملها؟
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أي من الخيارات التالية يتعلق بوظيفة الخلايا الليمفاوية البائية بشكل مباشر؟
أي من الخيارات التالية يتعلق بوظيفة الخلايا الليمفاوية البائية بشكل مباشر؟
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ما هو تأثير الخلايا الليمفاوية البائية على المناعة؟
ما هو تأثير الخلايا الليمفاوية البائية على المناعة؟
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Study Notes
Introduction
- The human immune system is designed to protect the body from bacteria, viruses, and abnormal cells that may develop within the body.
- The comprehensive host defense system includes physical and chemical barriers to infection, as well as biological and cellular responses, in addition to the immune response.
- Some of these layers of host cell defense are general and designed to confront any foreign organism, while others are highly specific to certain organisms.
First Line of Defense
- The first line of defense involves the skin and mucous membranes that protect openings in the body.
- Mucous membranes cover secretions like sticky mucus, which traps invading organisms, and digestive enzymes such as lysozymes, often found within mucous membrane secretions.
- If organisms penetrate the first line of defense, they encounter phagocytes, white blood cells, antimicrobial agents, and natural killer cells, all attacking foreign organisms in a non-specific manner.
- Specialized cells called lymphocytes and antimicrobial proteins also target foreign organisms in a highly specific and unique manner.
- The entry of these foreign organisms into the body may lead to a significant inflammatory response and fever, both of which are also protective.
Antigens
- An antigen is any substance capable of stimulating an immune response.
- Strong antigens are large, complex molecules, often proteins and carbohydrates.
- Specific molecules on bacteria, viruses, pollen, plants, and insect venom can all act as antigens.
- The specific portion of the antigen that initiates the immune response is called the epitope.
Haptens
- A hapten is a small, low molecular weight molecule that can only trigger an immune response when attached to a larger molecule called a carrier.
- A known example of hapten is urushiol, the irritant found in poison ivy.
- When absorbed through the skin from poison ivy, urushiol undergoes oxidation in skin cells to produce a true hapten – a reactive molecule called a quinone.
- This quinone then reacts with skin proteins to form hapten-containing complexes.
Major Histocompatibility Complex (MHC)
- The MHC is a group of unique glycoproteins found on the surface of cells.
- Each person has a unique MHC.
- The MHC was originally called the leukocyte antigen (HLA) because it was first identified on the surface of white blood cells.
- Two distinct types of the MHC are found on cells: MHC I and MHC II.
MHC Class I
- MHC I is found on almost all nucleated cells within the body.
- It acts as a self-marker for the immune system (identifying a cell as normal and belonging to the body).
- Foreign organisms like viruses often express some of their antigens on the MHC I of the cells they infect.
- This change in MHC I signals the immune cells that a particular cell has been infected and is no longer normal.
MHC Class II
- MHC II is found only on antigen-presenting cells (APCs), thus presenting foreign antigens to other immune cells, particularly helper T lymphocytes, which in turn activate other immune cells.
- They work together to combat foreign entities.
- Macrophages are a prime example of MHC II.
Macrophages and Monocytes
- When macrophages engulf a foreign organism, they destroy it and break it down into small peptides.
- They extract the antigenic portion and present it on their cell surface using their MHC II, which acts as a billboard.
- Macrophages displaying foreign antigens on MHC II are called antigen-presenting cells (APCs).
Lymphocytes
- Two distinct subsets of T lymphocytes exist:
- Helper T cells: Express a unique protein cluster called CD4 on their surface. CD stands for cluster of differentiation, a way to identify different lymphocyte types.
- Cytotoxic T cells: Express the CD8 protein on their surface.
- Helper T cells can recognize the antigen on the surface of macrophages by binding to the antigen presented on the phagocytes' surface through the T cell receptor (TCR). During this process, phagocytes secrete cytokines, such as interleukin-1 (IL-1), which partially stimulates helper T cells. Subsequently, helper T cells bind to the surface proteins of phagocytes (B7) using their own surface proteins (CD28), thus becoming fully stimulated.
- Helper T cells secrete another interleukin, IL-2, which in turn stimulates B lymphocytes to produce memory cells that retain all information about the attacking foreign organism. These memory cells also transform into plasma cells which, in turn, differentiate to produce antibodies.
- Activated helper T cells also produce cytokines that stimulate phagocyte activity, cytotoxic T cells, and natural killer cells.
- Cytotoxic T cells are activated by cytokines from helper T cells.
- Activated cytotoxic T cells recognize the foreign antigen presented on infected cells via MHC I.
- They directly destroy infected host cells by releasing cytotoxic cytokines, cell-digesting enzymes, and proteins called perforins, which puncture and destroy the infected cell.
B Lymphocytes
- When B cells encounter a foreign antigen, they bind to it.
- Under the influence of cytokines released by helper T cells, they mature into plasma cells that produce antibodies.
- A small subset of activated B cells become memory B cells, remaining in the body for extended periods, able to quickly recognize and respond to the same antigen if encountered later.
Antibodies
- Antibodies, also known as immunoglobulins, are globular proteins produced by activated B cells (plasma cells).
- Antibodies bind to viruses, bacteria, and toxins to inhibit their action.
- All antibodies share a basic, common structure consisting of two major regions: a constant region (FC) and a variable region (Fab).
Antibody Classes
- IgA: Predominant in bodily secretions (saliva, respiratory secretions, mother's milk, digestive tract, tears) to protect the infant in early life, protecting mucous membranes. Represents approximately 10-15% of all antibodies.
- IgG: A major class of antibodies responsible for the immune response, acting against viruses, bacteria, and toxins. Crosses the placenta, providing protection for the fetus. It assists killer cells in eliminating infectious agents. Represents about 80% of all antibodies. Its small molecular weight enables tissue diffusion.
- IgM: The largest antibody, found in blood and lymph, and due to its large size, is usually not distributed widely. The first antibody produced in an immune response and the first antibody in a fetus. Associated with innate immunity, such as ABO blood group reactions. Represents about 10% of all antibodies.
- IgE: Attaches to mast cells in the lungs, skin, and mucous membranes, thus involved in allergic reactions. The body overproduces it in response to environmental antigens. Represents less than 1% of all antibodies.
- IgD: Its role in immune function is not fully understood, but it's essential for B cell maturation. Represents less than 1% of all antibodies.
Natural Killer Cells
- A non-specific type of lymphocyte that destroys all foreign organisms without selectivity by releasing cytotoxic chemicals and cytokines.
- Thus it plays a role in natural immunity.
- Recognizes cells identified as "foreign" (e.g., altered, loss of MHC I) by binding and destroying antibody-coated target cells.
Cytokines
- Cytokines are proteins that act as communicators between cells in the body, particularly between white blood cells of the immune system secreted by immune cells (T cells, macrophages) fighting cancer, viruses, and microbes.
- This large family includes interleukins (ILs), interferons (IFNs), and growth factors.
- Their functions include maintaining normal immune cell growth, migration, health, and vitality.
- They can elevate body temperature, acting as important inflammatory mediators.
Complement System
- A system of over 20 plasma proteins produced in the liver, each designated with a "C" and numbered. They are activated in a cascade.
- When antibodies (IgM or IgG) bind to an antigen, C1 binds to the complex (antigen-antibody complex) and activates a cascade. C3a is released to attract phagocytes to the site for attacking foreign bodies.
- C3a activates the next protein, C5, which combines with C6,7,8,9 to form the membrane attack complex. This complex creates a pore in the target cell membrane, allowing water entry and causing the target cell to burst.
- Activated complement proteins have several functions including:
- lysis of mast cells.
- lysis of bacterial cells.
Inflammatory Response
- Inflammation is the body's tissue response to injury.
- Important although painful, the inflammatory response is crucial for preventing infection at the site of injury, and initiating the healing process.
- Five signs of inflammation:
- Redness: Increased blood flow to the inflamed area.
- Swelling: Edema, increased blood vessel permeability, and fluid accumulation.
- Heat: Increased temperature due to increased blood flow to the inflamed area.
- Pain: Stimulation of sensory nerves in the inflamed area.
- Loss of function: Impaired function of inflamed tissues.
- The inflammatory response has two main phases:
- Vascular response: Initial phase
- Cellular response: Subsequent phase
- Key aspects of the vascular response include:
- Immediate, rapid constriction, followed by dilation of blood vessels in the affected area.
- Increased permeability of capillaries in the affected area – resulting in swelling and edema. The fluid entering the affected area helps dilute or remove toxins or irritants in the tissues.
Hypersensitivity Reactions
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A hypersensitivity reaction is an exaggerated and abnormal immune response.
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Hypersensitivity reactions can be immediate or delayed for days. They are often called allergic reactions. Four types exist.
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Type I Hypersensitivity: Involves an immediate immune response to an antigen mediated by IgE antibodies bound to mast cells. These cells contain significant amounts of inflammatory mediators (e.g., histamine) and other substances that promote inflammation. Binding of an allergen to IgE bound to mast cells causes mast cell degranulation, releasing inflammatory mediators into the tissues. The response includes circulating mediators, also releasing histamine, which could play a role in this reaction.
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Examples of type I reactions include atopic dermatitis, food allergies, and allergic rhinitis. Severe type I hypersensitivity, anaphylaxis is life-threatening and involves rapid release of histamine and other inflammatory mediators from IgE-bound mast cells.
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Type II Hypersensitivity: These tissue-specific reactions involve IgG or IgM antibodies targeting antigens on cell surfaces. Antibody binding activates complement and subsequent cell lysis. Examples include blood transfusion reactions (ABO incompatibility) and hemolytic disease of the newborn (incompatibility of mother and child's RH proteins).
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Type III Hypersensitivity: This occurs when an antigen-antibody complex forms outside the circulatory system and deposits in blood vessel walls or tissues. Immune complexes also activate the complement system and, subsequently cell damage and damage.
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Immune complexes may become trapped in glomeruli. The resulting inflammation can lead to kidney damage. Examples: acute glomerulonephritis, systemic lupus erythematosus (an autoimmune condition in which immune complexes form and target collagen in the body), and serum sickness (a condition in which antibodies form against external substances in the blood like medications, vaccines, and foreign blood antigens.
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Type IV Hypersensitivity: Also called delayed-type hypersensitivity, is mediated by T lymphocytes. Activated cytotoxic (CD8) or helper (CD4) T cells are stimulated by exposure to a foreign antigen. The activated cells release inflammatory cytokines leading to activation of other immune cells and the coagulation cascade. The end result is tissue inflammation (and potentially damage) that may take hours or days to develop. Examples: autoimmune thyroiditis (Hashimoto's disease), delayed hypersensitivity reactions (poison ivy), and reactions in skin tuberculin tests to detect tuberculosis (the test injects a small portion of protein from the bacteria into the skin. If the bacteria enters through the skin, it causes a delayed-type hypersensitivity reaction in the skin).
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هذا الاختبار يستعرض نظام المناعة البشري وآليات الدفاع المختلفة التي يمتلكها الجسم. يتناول الخط الأول من الدفاع، بما في ذلك وظائف الجلد والأغشية المخاطية في مواجهة الكائنات الغريبة. يتم توضيح كيفية استجابة الجسم باستخدام خلايا الدم البيضاء والمواد المضادة للميكروبات.