introduction to immunology jan. 19 reading: chapter 1
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Introduction to immunology
Jan. 19Reading: Chapter 1
Objectives
• Compare and contrast the general functions of different types of immune cells
• Summarize the roles of: – innate versus adapative immunity– cellular versus humoral immunity
History of immunology• Early observers noticed that
survivors of certain diseases were resistant to re-infection
Mary Wortley Montagu
Excerpt from a letter by M. W. Montagu, 1717:“….The old woman comes with a nutshell full of the matter of the best sort of smallpox and asks what veins you please to have opened. She… puts into the vein as much venom as can lie upon the head of her needle. …You may believe I am very well satisfied of the safety of the experiment since I intend to try it on my dear little son. …I should not fail to write to some of our doctors very particularly about it if I knew any one of 'em that I thought had virtue enough to destroy such a considerable branch of their revenue for the good of mankind….”
http://www.foundersofscience.net/lady_mary_montagu.htm
History of immunology• Edward Jenner, 1796
– 1st vaccinations: cowpox (vaccinia) • Louis Pasteur, 1880s
– Vaccines against cholera in chickens, rabies
• Emil von Behring & Shibasaburo Kitasato, 1890
– Serum from animals immune to diptheria or tetanus conferred immunity to recipients
– “Antitoxic activity” = antibodies
History of immunology
• Eli Metchnikoff (shared Nobel Prize, 1908)
– Phagocytic cells
• Paul Erlich (shared Nobel Prize, 1908)
– Described different types of immune cells, antibodies
Components of the immune system
• Lymphoid cells– Lymphocytes
• Myeloid cells– Granulocytes– Monocytes/macrophages– Dendritic cells
http://www.mhhe.com/biosci/ap/histology_mh/wbc1.html
Hematopoiesis
General functions of immune cells
General functions of immune cells
Lymphocytes are small and inactive unless antigen recognition occurs
General functions of immune cells
Primary lymphoid tissues
Secondary (peripheral) lymphoid tissues
Components of the immune system: Lymphoid tissues
Inflammation is triggered by infection
Lymphocytes encounter antigens in the peripheral
lymphoid tissues
Two general types of immunity
• Innate (natural, native)
• Adaptive (specific, acquired)
Innate vs adaptive immunity
Innate immunity
Adaptive immunity
Response time
Number of specificities
Specificity improves
during response
Memory responses
Innate immunity
• Phagocytes (macrophages, neutrophils, dendritic cells)
–Engulf microbes or foreign particles–Release proinflammatory cytokines,
chemokines• Complement• Inflammation (early)• Antigen processing and presentation
Antigen presentation• T cell receptors
cannot bind antigens in the native state
• Must be processed and presented on an MHC protein
• Antigen presenting cells (APCs)– Crucial bridge
between innate and adaptive immunity
Adaptive immunity
• APCs required• Lymphocytes activated• Effector mechanisms respond to
different types of pathogens– Humoral (B cells, antibodies)– Cell-mediated (T cells)
• Memory cells generated
Adaptive immunity
• Lymphocyte activation– Clonal selection and
clonal expansion
Adaptive immunity: humoral responses
• Cytotoxic T cells (CD8+, CTL)– Recognize antigens
presented by MHC I– Response to
cytosolic pathogens
– Directly lyse target cells
Adaptive immunity: cell-mediated immunity
• Helper T cells (CD4+)– Recognize antigens
presented by MHC II– Response to extracellular
pathogens– 3 major classes:
• TH1
• TH2
• Regulatory T cells
– Boost proliferation and function of other immune cells
Adaptive immunity: cell-mediated immunity
Immune-related diseases
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