Your Immune System: Key Defenders Against Infection

The immune system is a coordinated network of cells, proteins, and barriers that protect against pathogens.

Cellular Defenders

• Neutrophils: First responders; phagocytose bacteria/fungi.
• Lymphocytes:
  • B cells → produce antibodies.
  • T cells (CD4⁺ helpers, CD8⁺ cytotoxic) → coordinate and kill infected cells.
• Natural Killer (NK) cells: Detect and destroy virus-infected/cancerous cells without prior sensitization.
• Phagocytes (macrophages, dendritic cells): Engulf pathogens, present antigens.

Molecular Weapons

• Antibodies (immunoglobulins): Neutralize toxins, opsonize pathogens, activate complement.
• Complement proteins: Lyse pathogens, enhance phagocytosis, recruit immune cells.
• Cytokines: Signaling molecules (interleukins, interferons, TNF) that orchestrate responses.

First-Line Barriers

• Skin and mucous membranes (physical block).
• Stomach acid, lysozyme in tears/saliva (chemical).
• Microbiome competition.

Immunological memory (memory B/T cells) enables faster, stronger responses upon re-exposure.