Chapter 57

Immunology

Card 1 of 11Immune System Physiology

Chapter Opening

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The cells of immunity

Cells of the Immune System

Immunogens cause a specific immune response; antigens interact with the products of that response (each may have several epitopes). Haptens are small molecules (like penicillin) that become immunogenic only when linked to a carrier protein. The leukocytes derive from bone marrow stem cells: granulocytes (neutrophils, eosinophils, basophils), monocytes/macrophages, dendritic cells, mast cells, natural killer (NK) cells, and lymphocytes (B and T cells).

🦠Neutrophils (PMNs): most numerous; rapid phagocytosis at inflammation sites

🧹Macrophages: phagocytose debris; antigen-presenting cells; secrete cytokines

🌳Dendritic cells: the most effective initiators of T-cell responses

💥Mast cells: histamine and TNF-alpha granules; drive type I hypersensitivity with IgE

Haptens Need a Carrier

A hapten (such as penicillin or poison ivy's urushiol) is too small to be immunogenic alone but becomes immunogenic when bound to a carrier protein. The most potent immunogens are large (> 5000 Da) proteins. Adjuvants are substances that enhance immunogenicity.

📖 “Immunogen: causes immune response. Antigen: interacts with response products (epitopes). Hapten: small (penicillin/urushiol), immunogenic only with carrier protein. Leukocytes: granulocytes (neutrophils/PMN phagocytose, eosinophils=parasites/allergy, basophils), monocytes/macrophages (phagocytose, APC, cytokines), dendritic cells (best T-cell initiators), mast cells (histamine/TNF, type I hypersensitivity), NK cells, lymphocytes.”