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Lecture 1c: Categories of Immune Responses
Lecture 1c: Categories of Immune Responses

Lecture 1c: Categories of Immune Responses

Lecture 1c: Categories of Immune Responses

UCSD Extension School: Applied Immunology (BIOL-40371) Spring Quarter 2021 This introductory lecture presents an overview of the two arms of the immune system: innate immunity and adaptive immunity.


In this lecture, we explore innate and adaptive immunity, covering key immune cell types and their roles in countering infections. The focus is on the phases of immune responses: infection and inflammation, resolution, and immune memory.

Innate Immunity vs. Adaptive Immunity

Innate immunity is the immediate defense against various pathogens, while adaptive immunity offers a tailored response to specific pathogens.

Phases of Immune Response

  • Infection and Inflammation Phase: Detection of pathogens activates innate immune cells and defense mechanisms.
  • Resolution Phase: Anti-inflammatory signals restore balance after pathogen clearance.
  • Immune Memory Phase: Long-lasting memory cells provide future protection.

Innate Immunity Specifics and Functions

Innate immune responses are broad and triggered by pattern recognition receptors (PRRs), ensuring quick pathogen containment. Different from adaptive immunity, innate responses are genetically fixed.

Differentiation of Immune Cells

Hematopoietic stem cells generate immune cell types. Macrophages, neutrophils, dendritic cells, and natural killer (NK) cells play significant roles.

Categorizing Innate Immune Cell Types

Innate immune cell roles align with detecting pathogens, consuming them, and deploying cytotoxic effector molecules. Macrophages, dendritic cells, and neutrophils perform these functions.

Presenting Antigens via Professional Antigen-Presenting Cells (APCs)

Professional APCs like dendritic cells present antigens to activate adaptive immune cells. Macrophages also participate in antigen presentation.

Producing Cytokines and Chemokines

Leukocytes secrete cytokines and chemokines that influence immune cell activation and migration.

Adaptive Immune Response

Adaptive immune cells have a slower initial response but establish long-term memory. Specificity is achieved through lymphocyte antigen receptors.

B Cell Receptor and Antibody Secretion

B lymphocytes express the B-cell receptor (BCR), which binds directly to soluble antigens. Activated B cells secrete antibodies and form memory B cells.

Summary and Conclusion

Innate and adaptive immunity offer distinct defense mechanisms. Lecture 1d will delve into lymphoid organs and the lymphatic system’s role in immune cell distribution.

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