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What is the primary function of the complement system?
What is the primary function of the complement system?
Complement protein C3b promotes phagocytosis by decreasing adherence of pathogens to phagocytic cells.
Complement protein C3b promotes phagocytosis by decreasing adherence of pathogens to phagocytic cells.
False
What is opsonization in the context of the immune system?
What is opsonization in the context of the immune system?
The process of marking pathogens for destruction by phagocytic cells.
Complement activation requires several accessory factors, including __________.
Complement activation requires several accessory factors, including __________.
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Match the following components with their roles in the immune response:
Match the following components with their roles in the immune response:
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Which of the following is NOT a component of the innate immune system?
Which of the following is NOT a component of the innate immune system?
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The innate immune system is the first line of defense against pathogens.
The innate immune system is the first line of defense against pathogens.
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What do PAMPs or MAMPs stand for in the context of the immune response?
What do PAMPs or MAMPs stand for in the context of the immune response?
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The innate immune system includes physical barriers such as _______ and _______.
The innate immune system includes physical barriers such as _______ and _______.
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Match the following cellular components with their functions:
Match the following cellular components with their functions:
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Which type of lymphocytes are responsible for cell-mediated responses?
Which type of lymphocytes are responsible for cell-mediated responses?
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Which immune response involves the production of antibodies?
Which immune response involves the production of antibodies?
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Antibodies are produced by T cells.
Antibodies are produced by T cells.
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Cytokines are released as a response to the identification of pathogens by immune cells.
Cytokines are released as a response to the identification of pathogens by immune cells.
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What is the role of cytokines in the immune response?
What is the role of cytokines in the immune response?
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An __________ is a tiny portion of an antigen that interacts with antibodies.
An __________ is a tiny portion of an antigen that interacts with antibodies.
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Name one type of antimicrobial peptide produced by certain cell types in the innate immune system.
Name one type of antimicrobial peptide produced by certain cell types in the innate immune system.
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Match the following immune responses with their functions:
Match the following immune responses with their functions:
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What happens to B-cells that bind to a specific antigen?
What happens to B-cells that bind to a specific antigen?
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Memory B-cells provide a rapid response upon first exposure to an antigen.
Memory B-cells provide a rapid response upon first exposure to an antigen.
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Where are B-cells produced?
Where are B-cells produced?
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What is the primary function of cytotoxic T cells?
What is the primary function of cytotoxic T cells?
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Self-reactive T cells are promoted in the Thymus.
Self-reactive T cells are promoted in the Thymus.
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Where do T-cells and antigen-presenting cells (APCs) primarily meet?
Where do T-cells and antigen-presenting cells (APCs) primarily meet?
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The pathogen interacts with ______ cells to initiate a humoral immune response.
The pathogen interacts with ______ cells to initiate a humoral immune response.
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Which component is involved in the cell-mediated immune response?
Which component is involved in the cell-mediated immune response?
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Match the following immune cells with their respective functions:
Match the following immune cells with their respective functions:
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Cytotoxic T cells do not require the help of T-helper cells for activation.
Cytotoxic T cells do not require the help of T-helper cells for activation.
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What type of immune response is mediated by T-cells?
What type of immune response is mediated by T-cells?
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What type of T-cell is activated by MHC I on infected cells?
What type of T-cell is activated by MHC I on infected cells?
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T-helper cells can directly kill infected cells.
T-helper cells can directly kill infected cells.
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What do antigen presenting cells (APCs) use to present antigens to T-cells?
What do antigen presenting cells (APCs) use to present antigens to T-cells?
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Cytotoxic T-cells express the ______ co-receptor.
Cytotoxic T-cells express the ______ co-receptor.
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Match the following components with their primary roles:
Match the following components with their primary roles:
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Why do we need T-helper cells?
Why do we need T-helper cells?
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Any cell can present an antigen on MHC II molecules.
Any cell can present an antigen on MHC II molecules.
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What happens to activated T-helper cells after activation?
What happens to activated T-helper cells after activation?
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Study Notes
Complement System
- Thirty proteins produced by the liver circulate in the blood serum.
- These proteins recognize pathogens and trigger a cascade of events.
- Once activated, other components induce inflammation.
- Signals attract immune cells to the site of infection.
- Pathogens are bound to enhance phagocytic cell activity via opsonization.
- Pathogens are lysed (broken down).
Opsonization
- Complement protein C3b or antibodies bound to a bacterial surface act as opsonins.
- This promotes adherence and phagocytosis.
Complement Activation
- Complement activation requires accessory factors.
- A diagram showing the 'alternative pathway' is included.
- A membrane attack complex is formed.
Innate Immunity - Summary I
- Antimicrobial peptides (AMPs), lysozymes and lipases kill bacteria.
- Microbe-associated molecular patterns (MAMPs) are recognized by phagocytic cells.
- Examples of MAMPs are lipopolysaccharide (LPS), flagellin, and CpG motifs.
- Complement proteins are involved in the inflammatory response.
Innate Immune Components - Summary II
- Thick epithelium and tight junctions are physical barriers
- Lysozyme and AMPs (antimicrobial peptides) are chemical barriers
- Phagocytes such as neutrophils, macrophages, and dendritic cells play a vital role as cellular components of the innate immune system.
- C3, C5 complement proteins and other helper proteins are involved in complement activation.
Summary III
- Mechanical, chemical, and microbiota barriers act as the first line of defence against microbial invasion.
- Acellular responses involve the production of antimicrobial peptides and complement proteins.
- Cellular responses involve recognition of microbial associated molecular patterns (PAMPs or MAMPs) by receptor proteins on immune cells. Inflammation is triggered when invader recognition is accomplished.
Adaptive Immunity
- Adaptive immune response introduction includes B-cells, T-cells and antibodies.
- Includes: B cells and memory, T cells, cell mediated immunity.
Immune Cell Functions (Innate vs Adaptive)
- Innate immunity response is rapid (<10 hrs) and has a rapid initial response, a slow second response.
- Adaptive immunity response is slower (>72 hrs) and slower to develop; however, the response is strong and faster on subsequent exposures.
Cells of the Immune System
- Stem cells differentiate into lymphocytes, B cells, T cells and natural killer cells (NK).
- B cell progenitors mature into plasma cells.
Adaptive Immune Response - Main Players
- Lymphocytes (T cells) include cell-mediated responses.
- B lymphocytes (B cells) include humoral responses (antibodies)
- Antibodies are produced by B-cells
- Cytokines are signal molecules.
Antibody Architecture
- Antibodies recognize diverse non-host structures.
- Antibodies contain variable regions to bind to antigens.
- Each antibody recognizes a unique epitope (the part of the antigen it binds).
Antibodies and Foreign Particles
- Antigens are foreign compounds (like proteins) which trigger adaptive immune responses.
- Epitopes are the specific sites on antigens which antibodies recognize.
Humoral Response: Antibody Binding
- Humoral response neutralizes threats with antibody binding.
- Three main approaches antibodies use to clear an infective agent include opsonization, neutralization, and complement activation (ONC).
Snake Antivenom
- Antibodies are used to neutralize snake venom toxins.
B-Cells and Humoral Immune Response
- B-cells develop in bone marrow and carry B-cell receptors.
- When a B-cell receptor (BCR) binds to a specific antigen, it differentiates into plasma cells and memory cells.
- Plasma cells produce antibodies.
Antibody Antigen Recognition
- B-cells with diverse antibody structures are made in bone marrow.
- Self-reactive B cells are removed in bone marrow.
- Antigens bind to B cells, this triggers clonal propagation and somatic hypermutation - resulting in better antibodies.
Antigen Binding and B cells
- Antigen binding to B-cells triggers clonal propagation and somatic hypermutation (process refining an antibody).
- B-cells differentiate into plasma and memory cells.
Memory B-Cells
- The likely advantage of memory B-cells is the rapid response to subsequent exposures to the same pathogen.
- Existing memory cells produce refined antibodies rapidly, quickly addressing the pathogen.
T-Cells and Cell-Mediated Immune Response
- T cells develop in the bone marrow and have T-cell receptors on their surface.
- T cells bind to receptors on antigen presenting cells (APC).
- Once a T cell receptor (TCR) binds to an antigen, the T cell differentiates either to either kill infected cells or activate other cells.
T-Cell Antigen Recognition
- T cells develop specialized T cell receptors (TCR) in the thymus.
- Self-reactive T cells are eliminated during development in the thymus.
Antigen Presenting Cells (APCs)
- T cells encounter their antigens by interacting with APCs like dendritic cells, which display antigens on MHC molecules.
- MHC molecules present antigens to T cells.
APC Antigen Presentation
- APCs present antigens on MHC molecules to T cells.
- MHC II is a major histocompatibility complex molecule.
T-Cell Activation
- Antigen presenting cells display antigens on the MHC II receptor.
- T cells with the right receptor are activated to divide and become effector T-cells (some becoming memory).
T-Helper Cells (B-cell Activation)
- T-helper cells activate B cells to differentiate into plasma and memory cells.
- This process requires the presentation of antigen fragments by MHC II molecules to T helper cells.
Why Two Events for Immune Response
- The two events (B and T-cell recognition) are necessary for a robust and effective immune response.
Cell-Mediated Immunity
- Cytotoxic T cells kill infected cells by producing cytokines and perforins/granzymes that destroy the target cell.
- Activated effector cytotoxic T cells release cytokines to activate other cytotoxic T cells.
T-Cell Receptor Antigen Recognition
- T-cell receptors develop in the thymus, a specialized site for T-cell maturation.
- Self-reactive T cells are eliminated in the thymus.
T-Cells and APC Meeting Locations
- T-cells and APCs meet in lymphoid tissues and lymph nodes.
- Specific maturation sites for B and T cells are in the bone marrow and thymus, respectively.
- Mature T cells and APCs migrate to lymphoid tissues where they can interact.
Dendritic Cell Migration
- Immature dendritic cells reside in peripheral tissues.
- As infection progresses, dendritic cells migrate to lymph nodes for activation of T cells.
Cytotoxic T Cells
- Cytotoxic T cells search for target cells.
- Cytotoxic T cells release perforin and granzymes to kill target cells.
Transplant Patient Medications
- Transplant patients often take medications to suppress cytotoxic T cells to prevent rejection of the transplanted organ.
- Cytotoxic T-cells often recognize a transplanted organ as foreign and thus destroy it, requiring immunosuppression.
Putting it Together: Humoral Response
- The humoral response involves B cells, memory B cells, and T helper cells.
- The ONC activity (opsonization, neutralization, complement activation) is the central strategy of the humoral response.
Putting it Together: Cell-Mediated Response
- The cell-mediated response is led by cytotoxic T-cells (CD8+).
- Cytotoxic T-cells are activated when helper T-cells (CD4+) detect an infection's presence, triggering the activation of cytotoxic cells.
- Helper T cells are needed for cytotoxic T cell activation.
Summary
- The humoral response, mediated by B-cells and antibodies, neutralizes toxins and pathogens.
- The cell-mediated response, performed by T-cells (cytotoxic and helper), directly attacks infected cells.
- The immune system has memory, improving responses to subsequent pathogen encounters.
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Description
Test your knowledge on the functions and components of the immune system with this quiz. Learn about the roles of the innate and adaptive immune responses, as well as the importance of complement proteins and antibodies. Challenge yourself with matching components to their functions and exploring key terms.
