Inflammatory Response in Immunology

Inflammatory Response

• Inflammation is a crucial component of the innate immune system, triggered by injury to vascularized tissues.
• It is a rapid, non-specific process aimed at containing damage, eliminating pathogens, and initiating healing.
• Key features include activation within seconds of injury, vascular changes (vasodilation, increased capillary permeability), and cellular events (leukocyte recruitment and phagocytosis).
• Cytokines (signaling molecules) regulate the immune response. Pro-inflammatory cytokines (TNF-α, IL-1) amplify the response, while anti-inflammatory cytokines (IL-10, TGF-β) dampen it.

Acute/Chronic Inflammation

• Acute inflammation is characterized by redness, swelling, heat, pain, and loss of function.
• Inflammation is a protective response, neutralizing microorganisms and promoting tissue repair.
• It resolves within days.
• Chronic inflammation can result from unresolved acute inflammation or persistent triggers (infections, autoimmune diseases).
• It's characterized by the infiltration of lymphocytes and macrophages, connective tissue formation, and epithelial cell proliferation.
• Granulomatous chronic inflammation involves macrophages and eosinophils walling off foreign bodies or infected areas.

Cells Involved in Inflammation

• Mast cells release histamine and cytokines, increasing vascular permeability.
• Macrophages engulf pathogens and debris, and presenting antigens for adaptive immune response.
• Neutrophils are effective phagocytes, releasing ROS for pathogen destruction, though can damage tissue.
• Dendritic cells bridge innate and adaptive immune systems, initiating the adaptive immune response.
• Eosinophils regulate vascular mediators from mast cells and play a role in allergic reactions, though can damage tissue.

Innate Immune System

• The innate immune system is the body's first line of defense against injury and infection.
• It's characterized by physical and biochemical barriers, the microbiome, and cells such as mast cells, macrophages, and dendritic cells
• It provides an immediate, non-specific response.

Adaptive Immune System

• The adaptive immune system provides a more specific and long-lasting response to pathogens through lymphocytes, including T cells (that mature in the thymus) and B cells (that mature in the bone marrow).
• T cells differentiate into various types, including helper and cytotoxic T cells.
• B cells differentiate into plasma cells and memory B cells that produce antibodies.

Hypersensitivity Reactions

• Hypersensitivity reactions are inappropriate immune responses to antigens that damage tissues, categorized into Type I-IV.
• Type I (immediate hypersensitivity) is IgE-mediated; examples include allergic rhinitis and asthma. (causes inflammation, such as in the airways).
• Type II (tissue-specific hypersensitivity) - antibodies directed against self or foreign antigens on specific cells/tissues can lead to cell destruction or dysfunction, mediated by IgG or IgM.
• Type III (immune complex hypersensitivity) involves antigen-antibody complexes which deposit in tissues, activating complement and leading to inflammation
• Type IV (cell-mediated hypersensitivity) is cell-mediated and results in delayed reactions such as in allergic contact dermatitis or in response to intracellular pathogens.
• Sensitization occurs with the first exposure to an antigen.
• Clinical manifestations of Type I hypersensitivity reactions include vascular changes, increased vascular permeability etc.
• Clinical manifestations of Type II hypersensitivity reactions include tissue damage or dysfunction (such as in blood transfusion reactions).
• Clinical manifestations of Type III hypersensitivity reactions include inflammation and organ damage
• Clinical manifestations of Type IV hypersensitivity reactions include inflammation and cell death.

Cachexia

• Cachexia is a complex metabolic disorder characterized by muscle wasting and atrophy with energy imbalance.

HIV/AIDS

• HIV is a retrovirus that infects and destroys CD4+ T cells of the adaptive immune system, weakening the immune system.
• This leaves the body vulnerable to opportunistic infections.

Infection Concepts

• Factors influencing infection include communicability, immunogenicity, infectivity, pathogenicity, and portal of entry.
• Other factors include Virulence, ID50 or Infectious Dose, and Toxigenicity.

Epidermis

• The epidermis is the outermost layer of the skin, acting as a defensive barrier.
• Keratinocytes are the predominant cells, producing keratin and providing structural support and water resistance.
• Melanocytes produce melanin, shielding deeper cells from UV radiation.
• Langerhans and Merkel cells also play important roles in the epidermis.

Viral Skin Infections

• Common viral skin infections include those caused by HSV, VZV, and HPV, all causing inflammation
• These infections can disrupt the immune system as well.

Fungal Skin Infections

• Dermatophytes are fungi that cause superficial skin infections like athletes foot, ringworm, or jock itch.
• Candidiasis is another fungal infection that can cause skin and mucosal infections.

Skin Cancer

• Skin cancers, such as basal cell carcinoma and squamous cell carcinoma, develop from epidermal cells and are linked to UV radiation exposure.
• Melanoma, originating from melanocytes, is characterized by its high ability to spread.

Psoriasis

• Chronic inflammatory skin disorder characterized by excess skin cell production, leading to thick, red, itchy plaques
• Can appear on various body parts.

Atherosclerosis

• Atherosclerosis is a disease of the arteries where arterial walls build up plaque.
• Smoking, hypertension, diabetes, high cholesterol, and family history are key risk factors.

Acute Coronary Syndromes

• This occurs when there is sudden blockage in coronary arteries leading to insufficient blood to the heart and cause chest pain
• Stable coronary artery disease: narrowing or blockage in coronary arteries is stable and does not lead to sudden blockage or reduced blood flow.
• Unstable coronary artery disease: narrowing or blockage in coronary arteries is unstable.
• Myocardial infarction is defined by sustained ischemia, myocyte necrosis, and death.

Hypertension

• Hypertension is a condition where the blood pressure is elevated, putting stress on blood vessels.
• Hypertension is characterized by persistently high blood pressure (a reading of 140/90 mmHg or higher).

Deep Vein Thrombosis

• Deep vein thrombosis (DVT) is characterized by blood clots forming in deep veins, often in the legs.
• DVT is caused by venous stasis, venous endothelial damage, and hypercoagulable states (that change blood from fluid to solid).

Left-Sided Heart Failure

• Left-sided heart failure arises when the heart struggles to pump enough blood, leading to decreased contractility, increased preload, and increased afterload.

Right-Sided Heart Failure

• Right-sided heart failure occurs when the right ventricle struggles to pump blood, often due to lung disease.

Pulmonary Hypertension

• Pulmonary hypertension is a rise in blood pressure in the vessels of the lungs
• This causes problems with pumping blood throughout and can also be a result of chronic inflammation.

Urinary Tract Obstructions

• Urinary tract obstructions can lead to conditions such as nephrolithiasis (kidney stones) or various issues in the lower urinary tract (from anatomical problems with the prostate urethra to the bladder).

Glomerulonephritis

• Glomerulonephritis is characterized by the inflammation of the glomeruli in the kidneys, leading to increased permeability of these units.

Acute & Chronic Kidney Injuries

• Acute kidney injury and chronic kidney disease encompass a spectrum of conditions that negatively affect kidney function
• Many underlying diseases (diabetes, high blood pressure, etc.) influence the development of kidney diseases
• Often involve inflammation, fluid imbalances, increased/decreased permeability.

Viral Hepatitis

• Viral hepatitis (A, B, C, D, E, or G) is a contagious viral infection of the liver, causing inflammation.
• Transmission varies depending on the hepatitis type (fecal-oral route, blood-to-blood contact).

Explore the intricate processes of the inflammatory response as a critical aspect of the innate immune system. This quiz covers the characteristics of acute and chronic inflammation, including key cellular events and the roles of various cytokines in the healing process.