Immune response to infection
Start with the big picture
Innate immunity responds early by recognizing conserved pathogen patterns through pattern-recognition receptors, which can trigger inflammatory signaling. Neutrophils, macrophages, dendritic cells, and natural killer cells contribute to rapid defense, while complement supports recruitment, opsonization, and pathogen lysis. Adaptive responses follow antigen presentation: MHC pathways activate CD4⁺ or CD8⁺ T cells, whose subsets and functions vary. B cells produce antibodies through T-dependent or T-independent activation, and antibody classes have distinct roles. Memory cells help make secondary antibody responses faster and stronger than primary responses. Together, these mechanisms provide a framework for understanding how immune defenses respond to infection.
What you'll learn
- Describe how pattern-recognition receptors initiate innate immune signaling.
- Outline the roles of innate effector cells, complement, and acute-phase reactants.
- Distinguish MHC I and MHC II antigen presentation and their T-cell targets.
- Compare major CD4⁺ T-cell subsets and CD8⁺ cytotoxic mechanisms.
- Explain B-cell activation, antibody classes, and primary versus secondary responses.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
