Your Body's Natural Defenses Against Disease: A Comprehensive Overview

The human body employs layered defenses against pathogens:

1. Physical & Chemical Barriers (Innate)

• Skin: Keratinized, acidic, antimicrobial peptides.
• Mucous membranes: Trap pathogens; ciliary clearance.
• Secretions: Saliva (lysozyme), tears (lysozyme), gastric acid, vaginal pH.

2. Innate Immune System (Rapid, Non-Specific)

• Phagocytes (neutrophils, macrophages): Engulf/destroy.
• Natural Killer (NK) cells: Kill infected/transformed cells.
• Inflammation: Recruits immune cells, increases perfusion.
• Fever: Inhibits some pathogens; enhances immunity.
• Interferons: Block viral replication in neighboring cells.
• Complement: Opsonization, lysis, chemotaxis.

3. Adaptive Immune System (Specific, Memory)

• Antigen presentation (dendritic cells, macrophages, B cells).
• B cells → antibodies: Neutralize, opsonize, activate complement.
• T cells: CD8+ cytotoxic (kill infected), CD4+ helper (orchestrate), Treg (regulate), memory.
• Immunological memory: Faster, stronger secondary response.

These integrated systems provide robust, multi-layered protection.