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Questions and Answers
What is the primary job of the immune system?
What is the primary job of the immune system?
Fight infections
What are foreign antigens?
What are foreign antigens?
Molecules not normally found in the body, such as viruses and bacteria.
Which cells are involved in the immune response?
Which cells are involved in the immune response?
The inflammatory response is specific to particular pathogens.
The inflammatory response is specific to particular pathogens.
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What does clonal selection focus on?
What does clonal selection focus on?
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What differentiates B cells after activation?
What differentiates B cells after activation?
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The main antibody found in bodily secretions is ______.
The main antibody found in bodily secretions is ______.
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What is the function of interleukin-2 (IL-2) in the immune response?
What is the function of interleukin-2 (IL-2) in the immune response?
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Which type of vaccine uses killed microbes?
Which type of vaccine uses killed microbes?
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Match the types of antibodies with their functions:
Match the types of antibodies with their functions:
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The secondary immune response is slower than the primary immune response.
The secondary immune response is slower than the primary immune response.
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What is the primary function of vaccines?
What is the primary function of vaccines?
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Vaccines can provide immediate protection against diseases.
Vaccines can provide immediate protection against diseases.
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What are the main phases of the immune response activated by vaccines?
What are the main phases of the immune response activated by vaccines?
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The immune system develops a 'memory' of the ______ after vaccination.
The immune system develops a 'memory' of the ______ after vaccination.
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Which type of immune response is triggered upon exposure to the actual microorganism after vaccination?
Which type of immune response is triggered upon exposure to the actual microorganism after vaccination?
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Study Notes
Immune System Functions
- The immune system acts like the body's security force, protecting against infection, destroying abnormal cells, and recognizing foreign tissues.
- The immune system can overreact, causing autoimmune responses, targeting healthy cells and triggering inflammation.
Inflammatory and Immune Response
- Inflammatory Response (Innate Immunity): is rapid, nonspecific, and lacks memory, involving various cells like neutrophils, macrophages, and platelets.
- Immune Response (Adaptive Immunity): is slower, specific, and has memory, involving lymphocytes and antibodies; also stimulated by vaccination.
Antigens
- Antigens are molecules recognized as foreign by the immune system, triggering immune responses involving lymphocytes and antibodies.
- Foreign Antigens are molecules not normally found in the body, such as viruses, bacteria, pollens, food, and drugs.
- Self-Antigens are molecules found on the surface of the body's own cells. The most important is the Human Leukocyte Antigen (HLA).
- HLAs are present on all cell membranes except red blood cells, helping the immune system distinguish between self and non-self.
- The Major Histocompatibility Complex (MHC) on chromosome 6 contains genes responsible for producing HLA antigens.
- RBC Antigens are found on the surface of red blood cells, responsible for blood types (A, B, and Rh).
Immune Response Mechanisms
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The immune system recognizes and destroys foreign invaders (antigens) through two main phases: generation of clonal diversity and clonal selection.
Generation of Clonal Diversity
- Involves the creation of a diverse population of lymphocytes, each capable of recognizing a specific antigen.
- Starts in the bone marrow with lymphoid stem cells that migrate to the primary lymphoid organs (thymus for T cells, bone marrow for B cells).
- Lymphocytes mature into immunocompetent T or B cells, each possessing a unique receptor specific for a single antigen.
- This results in a vast pool of lymphocytes, collectively able to recognize a wide range of foreign antigens.
- These mature lymphocytes circulate to secondary lymphoid tissues, awaiting activation by specific antigens during clonal selection.
Clonal Selection
- The process where the immune system focuses on specific threats:
- Antigen Encounter: The immune system is exposed to a specific antigen (a foreign substance).
- Antigen Presentation: Antigen-presenting cells (APCs) process and present the antigen to immature lymphocytes (B and T cells).
- Selection: The immune system selects B and T cells with receptors that specifically recognize the antigen.
- Clonal Expansion: These selected cells are stimulated to mature and multiply, creating a clone of cells specific to the antigen.
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Differentiation:
- B cells differentiate into plasma cells, which produce antibodies that target the antigen.
- T cells differentiate into cytotoxic T cells that directly kill infected cells, or other types of T cells that help coordinate the immune response.
- Immune Response: The antigen-selected cells mount a defense against the antigen.
- Memory Cells: Long-lasting memory B and T cells are produced, remembering the antigen and quickly mounting a response if the body is re-exposed to the same antigen in the future.
Antigen Processing and Presentation
- Antigen-presenting cells (APCs) engulf foreign invaders (antigens) through phagocytosis.
- The APC processes the antigen and displays fragments on its surface, attached to MHC Class II molecules.
- The APC releases interleukin-1 (IL-1), alerting other immune cells.
- Helper T cells (Th or CD4 cells) recognize the antigen-MHC Class II complex on the APC using their T cell receptors (TCRs).
- Activated Th cells release interleukin-2 (IL-2), stimulating them to mature into functional Th1 and Th2 cells.
Interleukin-2 (IL-2)
- IL-2 is a signaling molecule released by helper T cells (Th1 and Th2), promoting the growth and maturation of various immune cells.
- B lymphocytes (B cells) activated by Th2 cells, proliferate and differentiate into plasma cells.
- Plasma cells produce antibodies.
- T lymphocytes (T cells) activated by Th1 cells can differentiate into cytotoxic T (Tc or CD8 T cells) which destroy infected or cancerous cells directly.
- Memory Cells are long-lived B and T cells formed after an initial immune response, providing long-term immunity.
B Lymphocyte Response (Humoral Response)
- Activation: B cells are activated by T helper cells.
- Differentiation: Activated B cells differentiate into plasma cells.
- Antibody Production: Plasma cells produce immunoglobulins (antibodies).
Immunoglobulins (Antibodies)
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Immunoglobulins are glycoproteins produced by plasma cells.
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Antibodies are specific types of immunoglobulins that bind to a particular antigen.
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Antibodies consist of two main parts:
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Antigen-binding fragment (Fab): responsible for recognizing and binding to specific antigens.
- Contains specific regions called recognition sites that bind to matching antigens.
- The Fab's specific recognition sites give antibodies their specificity.
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Crystalline fragment (Fc): interacts with other immune cells to activate them.
- Can bind to complement proteins, helping to destroy pathogens.
- Interacts with immune cells like macrophages and neutrophils, triggering an inflammatory response.
Antibody Classes
- IgM: The first antibody produced during an immune response, found in blood and lymph fluid.
- IgG: The most common antibody, produced after IgM and responsible for long-term immunity.
- IgA: Found in bodily secretions like sweat, saliva, tears, and breast milk, protecting against infections in these areas.
- IgE: Involved in allergic reactions, binding to mast cells and basophils, triggering allergic symptoms.
Antibody Function
- Antibodies bind to specific antigens, forming antigen-antibody complexes.
- They neutralize pathogens by blocking their entry into cells or binding to their target sites.
- They can coat pathogens, making them more attractive to phagocytes, which engulf and destroy pathogens.
- They trigger the complement cascade, destroying pathogens.
Primary and Secondary Immune Responses
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Primary Immune Response: The first encounter with a specific antigen. The immune system produces mainly IgM antibodies.
- Antigenic Challenge: Contact with the antigen.
- Latent Period: A delay of about 5 days before a measurable amount of antibodies is produced.
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Secondary Immune Response: The second (or subsequent) encounter with the same antigen. The immune system produces mainly IgG antibodies.
- More rapid and larger production of immunoglobulins.
- The secondary immune response is much stronger and quicker than the primary response.
T Lymphocyte Response (Cellular Response)
- Cytotoxic T cells (Tc): Directly attack and kill cells displaying foreign antigens on their surface.
- Memory T cells (Tm): Remember past encounters with specific antigens, providing a faster, stronger immune response upon re-exposure.
T Lymphocytes: Td Cells and Treg Cells
- Td cells (Lymphokine-producing T cells): Likely Th1 cells, responsible for delayed hypersensitivity reactions.
- Treg cells (Regulatory T cells): Suppress the activation of B and T cells, regulating the immune system.
Natural Killer Cells (NK cells)
- NK cells are lymphocytes originating from lymphoid stem cells in the bone marrow.
- They account for about 10% of lymphocytes in the blood.
- They play a crucial role in fighting infections and cancer.
- They recognize and kill cells infected with viruses or that are cancerous.
- They detect changes in surface proteins of virally infected or stressed cells.
- They release interferon-gamma, helping macrophages kill the infected cell.
- They can directly kill infected and cancerous cells.
Vaccines
- Vaccines introduce a weakened or inactive form of a microbe into the body to trigger an immune response.
Types of Vaccines
- Inactivated Vaccines: Use killed microbes that still trigger an immune response.
- Live Attenuated Vaccines: Use weakened versions of the microbe that are less likely to cause disease.
- Toxoid Vaccines: Use inactivated toxins from bacteria.
- Subunit Vaccines: Contain only specific parts of the microbe, like proteins or polysaccharides.
- Conjugate Vaccines: Combine a weak part of the microbe with a strong part.
- Synthetic Vaccines: Use laboratory-made versions of antigens.
- DNA Vaccines: Contain genetic material from a virus or bacteria.
Vaccine Summary
| Type of Vaccine | Examples | Form of Protection |
|---|---|---|
| Inactivated or killed virus | Polio, hepatitis A | Antibody response |
| Inactivated or killed bacteria | Cholera, bubonic plague, pertussis | Antibody response |
| Live attenuated virus | Measles, mumps, rubella, varicella, flu, oral polio, rabies | Antibody and T cell response |
| Live attenuated bacteria | BCG vaccine for TB | Antibody and T cell response |
| Toxoid | Tetanus toxoid, diphtheria toxoid, rattlesnake venom | Antibody response |
| Subunit (antigen) vaccines | HPV | Antibody response |
| Conjugate vaccines | H.influenza type B | Th response |
| Synthetic vaccines | Hepatitis B, H1N1 | Antibody response |
| Viral vectors | Clinical trials of HIV antigen in canary pox vector | Antibody and T cell response |
| DNA vaccines | Clinical trials ongoing for several infections | Antibody and T cell response |
How Vaccines Work
- Vaccines introduce a weakened or inactive form of a pathogen into your body.
- Your immune system recognizes the antigen associated with the vaccine.
- It destroys the weakened vaccine.
- It develops a "memory" of the antigen.
- When you are exposed to the actual microorganism, your immune system mounts a rapid, potent secondary immune response.
- This response is much faster and stronger than the initial response to the vaccine.
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Description
This quiz explores the vital functions of the immune system, including its role in defending against infections and managing abnormal cells. It differentiates between innate and adaptive immunity, highlighting key processes like inflammation and the recognition of antigens. Test your knowledge and understanding of these essential biological concepts.
