Pathogens

Disease-causing or harmful microorganisms

Antigens

Material that can evoke an immune response

TWO BRANCHES OF THE IMMUNE SYSTEM

1) Innate Branch – non-specific, fast

• Physical barriers such as skin or chemical barriers
• Chemokines are a chemical signal produced by damaged cell to alert the body to danger and act as a homing signal for immune cells
• Neutrophils are the first type of phagocytic cell to arrive
• Monocytes arrive and mature into macrophages which engulf and destroy pathogens
• Inflammation (response to tissue damage) has four clinical signs: redness, heat, swelling and pain

2) Adaptive Branch – specific, slow, systemic, memory

• Humoral immunity – B cells (matured into plasma cells) producing antibodies (Y-shaped proteins)

• Cell-mediated immunity – Cytotoxic T cells recognize infected cells and kill them while helper T cells act as the general of the immune army and release chemical signals that activate various immune cell types