immune system mini lecture
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Columbia College mini-lecture
Philippe Henry PhD, Thursday April 9th 2015
A broad overview of the immune system
Based on chapters 1 & 2 of Kuby, Immunology (6th edition) 2007
Outline:- background on importance of the immune system
- innate and adaptive response
- cells of the immune system (time permitting)
The principal function of the immune system is to protect the host against pathogenic microbes.
Overview of the immune system
Immune system
Innate (nonspecific)
1st line of defense
Cellular components
Humoral components
Adaptive (specific)2nd line of defense
Cellular components
Humoral components
Innate immunity is present in all multicellular plants and animals but only vertebrates have adaptive immunity.
Innate Immunity is ubiquitous
6
Innate Immunity: cellular and molecular mechanisms predeployed before an infection and poised to prevent or eliminate the invader
- skin, mucous membranes, stomach acidity, phagocytes
- 1st line of defense
Adaptive Immunity: develops in response to infection and adapts to recognize, eliminate and remember the invading pathogen
- contingent on the innate response: signal
- antigen presenting cells, lymphocytes, antibodies
- 2nd line of defense
Innate Immune Response
• Recognition– Self/Non-self
Discrimination
• Response– Effector: neutralizes/
eliminates invader– Memory: prevents
second infection; “educates” the immune system for later attacks
Adaptive Immune Response
• Primary lymphoid organs: thymus and bone marrow is where lymphocytes mature
• Secondary lymphoid organs: lymph nodes, spleen, mucosa-associated lymphoid tissues and gut-associated lymphoid tissues provide sites for mature lymphocytes (antigenically committed) to interact with antigen
• Connected via lymphatic vessels and blood
Cells of the immune system
Immune system
Myeloid cells
Granulocytic
NeutrophilsBasophils
Monocytic
MacrophagesKupffer cells
Dendritic cells
Lymphoid cells
T cells
Helper cellsSuppressor cellsCytotoxic cells
B cells
Plasma cells
NK cells
-lymphocytes ( T and B) and antigen-presenting cells
-connect innate and adaptive responses
Key Cells & Overview of their Function
Major Phagocyte
Minor Phagocyte
Cells of the immune system: innate• Phagocytes
– Monocytes/macrophages– Dendritic cells
• Basophils and mast cells• Platelets• NK cells
Phagocytes – 1) macrophages• Ingest and digest
whole microbes and present Ag to helper T cells
• CD14
Phagocytes – 2) neutrophils
- first to arrive at site of injury playing a key role in the front-line defense against invading pathogens
- express & release cytokines: amplify inflammatory reactions by other cells
- release soluble anti-microbials
• Are complicated• Excellent phagocytes• Antigen-presenting cells
Phagocytes – 3) dendritic cells
Basophils and Mast cells
• Allergies• Mast cells are anti-
parasites• Mast cells are minor
phagocytes
Natural killer (NK) cells
• large granular lymphocytes
• Kill virus-infected or transformed cells (no Ag recognition receptors)
• Cytotoxicity mechanisms not well understood
Cells of the immune system: APC
• Cells that link the innate and adaptive arms– Antigen presenting cells (APCs)
• Heterogenous population with role in innate immunity and activation of Th cells
– Examples• Phagocytes like macrophages and dendritic cells• B cells
Cells of the immune system: adaptive
• Lymphocytes– B cells
• Plasma cells (Ab producing)– T cells
• Cytotoxic (CTL)• Helper (Th)
– Th1– Th2– Th17– T-reg
- B lymphocytes mature in bone marrow
- antigen binding receptor is a membrane bound Ab
- antigen presenting cell
- binding causes cell division and differentiation into memory B cells which produce secreted Ab
- T lymphocytes arise in bone marrow but migrate to the thymus gland to mature
- T-cell receptor (TCR): Th (CD4), Tc (CD8), T reg (CD4 + FoxP3)
- T cells don’t bind antigen directly like B cells but rather ONLY when the Ag is presented with MHC on APC
Thank you
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