Specific vs Non-Specific Immunity

• Innate immunity offers early protection from infection.
• Adaptive immunity develops more slowly and provides a more effective defense against infection.
• Non-specific protection of the body includes anatomical barriers, circulating effector cells and proteins, cytokines, and the inflammatory reaction.

Anatomical Barriers

• The skin and mucous membranes lining the respiratory, digestive, and genitourinary tracts are examples of anatomical barriers, which are the body's first line of defense.
• The skin's surface is protected by: hair, mucus, and various secretions
• Nasopharynx: contains lysozyme.
• Mucociliary Clearance: occurs in respiratory airways.
• Bile acids are synthesized in the liver.
• The stomach has disinfectant properties.
• Gut: peristalsis helps remove infectious agents.
• Blood-brain barrier: protects the nervous system from pathogens.

Circulating Effector Cells

• Neutrophil leukocytes, monocyte-macrophage cells, and natural killer cells (NK cells) are carriers of non-specific cellular protection.
• Neutrophilic leukocytes and monocyte-macrophage cells perform phagocytosis to protect non-specifically.

Phagocytosis

• Recognition, engulfment, and intracellular elimination of the pathogenic agent are the stages.
• Pathogenic agents are recognized directly or indirectly.
• Opsonins coat pathogens and facilitate phagocytosis, the coating process is known as opsonization.

NK (Natural Killer) Cells

• NK cells can kill infected, tumor, aged and damaged cells.
• NK cells synthesize and secrete IFNy, in response to IL-12

Circulating Effector Proteins

• Circulating effector proteins are non-specific humoral factors the extracellular fluid.
• Circulating effector proteins opsonize pathogens and, cause direct damage to pathogenic microorganisms.
• These proteins facilitate the chemotaxis of phagocytic cells to the site of infectious agents and tissue damage.
• Complement system proteins and acute phase proteins are important circulating effector proteins.

Complement System

• Composed of approximately twenty plasma proteins.
• Naturally in an inactive form.
• Three activation pathways: alternative, classical, and lectin.
• Alternative: non-specific protection.
• Classical: antigen-antibody complexes involved in specific protection.

Acute Phase Proteins

• Liver synthesizes them when influenced by pro-inflammatory cytokines.
• Acute phase proteins involved in positive chemotaxis, stimulate opsonization and adhesion of phagocytes, activate complement.
• For examples C reactive protein, mannose-binding lectin, alpha 1 antitrypsin, alpha 2 macroglobulin, fibrinogen and serum amyloid A.

Cytokines

• Soluble products that enable intercellular communication.
• Synthesized in response to stimulation.
• Autocrine: Self-stimulation by cells secreting the cytokine.
• Paracrine: Affecting nearby cells.
• Endocrine: Affecting distant cells via circulation.

Inflammation

• Tissue damage caused by physical, chemical, or biological agents triggers a non-specific inflammatory reaction to eliminate harmful effects and facilitate tissue repair.
• A non-specific defense mechanism that occurs as an organism's response to cell damage or death.
• Living tissue reacts to injury.
• Classified by origin (biological/non-biological factors) and duration (acute, subacute, chronic).

Acute Inflammation

• Characterized by vascular changes
• Swelling due to blood plasma movement into perivascular tissue.
• Accumulation of inflamatory cells and accelerated metabolic processes.
• Possible tissue/organ dysfunction occurs.

Vascular Changes

• Changes occur in the diameter of blood vessels and increases vascular permeability.
• Divided into early and late stages.

Mediators Of Inflammation

• Vasoactive amines (histamine).
• Plasma protein systems (complement system, kinin system, blood coagulation system).
• Arachidonic acid metabolites (prostaglandins, leukotrienes and thromboxane's).
• Cytokines.
• Some mediators are stored preformed in cells (e.g., histamine), while others are synthesized de novo (e.g., arachidonic acid metabolites).

Cardinal Signs Of Inflammation

• Includes redness (eritema), raised temperature (calor), pain, swelling (tumor), and loss of function.

Chronic Inflammation

• Long-term inflammation with active inflammation, tissue damage, and repair occurring simultaneously.
• Onset is gradual.
• Intensity is lower, and longer duration than acute inflammation.
• Characterized by predominance of proliferative changes,
• Unlike acute inflmmation characterized by a sudden onset and violent course, with a predominance of exudative changes.

Explore the key differences between specific and non-specific immunity, including defense mechanisms and the role of memory cells. Understand how specific immunity improves response in subsequent infections and the immune response activated when pathogens breach non-specific defenses.