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Questions and Answers
Which type of lymphocytes are responsible for humoral immune responses mediated by antibody molecules secreted by plasma cells?
Which type of lymphocytes are responsible for humoral immune responses mediated by antibody molecules secreted by plasma cells?
- CD8+ T cells
- T lymphocytes
- CD4+ T cells
- B lymphocytes (correct)
What is the key role of B cells in the immune system?
What is the key role of B cells in the immune system?
- Defence against extracellular pathogens (correct)
- Defence against intracellular pathogens
- Regulating the immune system
- Killing virally infected body cells
Which type of T cells are responsible for killing virally infected body cells?
Which type of T cells are responsible for killing virally infected body cells?
- B lymphocytes
- Helper T cells
- CD4+ T cells
- CD8+ T cells (correct)
What is the function of CD4+ T cells?
What is the function of CD4+ T cells?
How do B cells recognize and bind to antigens?
How do B cells recognize and bind to antigens?
How many copies of a specific BCR antibody do B cells express?
How many copies of a specific BCR antibody do B cells express?
What are antibodies composed of?
What are antibodies composed of?
What do antibodies bind to?
What do antibodies bind to?
Which region of the TCR forms the antigen binding site and is unique to each individual T cell?
Which region of the TCR forms the antigen binding site and is unique to each individual T cell?
What is the function of MHC/HLA molecules?
What is the function of MHC/HLA molecules?
How many copies of a single antigen receptor does a T cell express?
How many copies of a single antigen receptor does a T cell express?
What is the role of TCRs in recognizing antigens?
What is the role of TCRs in recognizing antigens?
What is another name for Major Histocompatibility Complex (MHC) molecules?
What is another name for Major Histocompatibility Complex (MHC) molecules?
What type of antigens can T cells recognize?
What type of antigens can T cells recognize?
What is the function of MHC molecules in relation to T cells?
What is the function of MHC molecules in relation to T cells?
What is the role of the hyper variable region in the TCR?
What is the role of the hyper variable region in the TCR?
What is the unique feature of each T cell's TCR?
What is the unique feature of each T cell's TCR?
What is the role of MHC molecules in relation to T cells?
What is the role of MHC molecules in relation to T cells?
What is the function of TCRs in recognizing antigens?
What is the function of TCRs in recognizing antigens?
What type of antigens can T cells recognize?
What type of antigens can T cells recognize?
What is the key role of B cells in the immune system?
What is the key role of B cells in the immune system?
What is the unique feature of each T cell's TCR?
What is the unique feature of each T cell's TCR?
What do antibodies bind to?
What do antibodies bind to?
What is the function of CD4+ T cells?
What is the function of CD4+ T cells?
What is another name for Major Histocompatibility Complex (MHC) molecules?
What is another name for Major Histocompatibility Complex (MHC) molecules?
What is the role of B lymphocytes in the adaptive immune system?
What is the role of B lymphocytes in the adaptive immune system?
What is the role of T lymphocytes in the immune system?
What is the role of T lymphocytes in the immune system?
What are the two types of T lymphocytes and what are their functions?
What are the two types of T lymphocytes and what are their functions?
What is the process by which B and T cells mature to distinguish self from non-self?
What is the process by which B and T cells mature to distinguish self from non-self?
How do acquired immune cells detect invading pathogens?
How do acquired immune cells detect invading pathogens?
What are antibodies and what is their structure?
What are antibodies and what is their structure?
How do B cells recognize and bind to antigens?
How do B cells recognize and bind to antigens?
What are the two types of antibodies that are the most abundant in the plasma?
What are the two types of antibodies that are the most abundant in the plasma?
Where do B cells mature in the body?
Where do B cells mature in the body?
Where do B and T lymphocytes exist in their inactive state?
Where do B and T lymphocytes exist in their inactive state?
Where and how do B and T cells get activated?
Where and how do B and T cells get activated?
What are the two processes that take place when B cells encounter antigen?
What are the two processes that take place when B cells encounter antigen?
Describe the processes of B cell activation followed by production of antibodies when it encounters antigens?
Describe the processes of B cell activation followed by production of antibodies when it encounters antigens?
What are the two activation signals for non protein antigens?
What are the two activation signals for non protein antigens?
What are the two activation signals in case of a protein antigen?
What are the two activation signals in case of a protein antigen?
What are the two functions antibodies use to help kill and eliminate antigens/pathogens?
What are the two functions antibodies use to help kill and eliminate antigens/pathogens?
What are the functions of IgM antibody?
What are the functions of IgM antibody?
What is the most abundant antibody in the plasma?
What is the most abundant antibody in the plasma?
What is the second most abundant antibody?
What is the second most abundant antibody?
What is the function of IgE antibody?
What is the function of IgE antibody?
What is the function of the IgA antibody?
What is the function of the IgA antibody?
What is the order of abundance of antibodies (Ig) in the blood plasma?
What is the order of abundance of antibodies (Ig) in the blood plasma?
What is the function of IgD antibodies?
What is the function of IgD antibodies?
What is the function of IgG antibodies?
What is the function of IgG antibodies?
What is the process of Natural Killer cell activation in innate immune response?
What is the process of Natural Killer cell activation in innate immune response?
What is the process of Natural killer cell activation in the adaptive (humoral) immune response of the body?
What is the process of Natural killer cell activation in the adaptive (humoral) immune response of the body?
What are the functions of CD4+ Helper T cells?
What are the functions of CD4+ Helper T cells?
What is the function of CD8+ Killer T cells?
What is the function of CD8+ Killer T cells?
What is the role of Regulatory T cells?
What is the role of Regulatory T cells?
What are the two types of MHC molecules and which T cells do they present peptide antigens to?
What are the two types of MHC molecules and which T cells do they present peptide antigens to?
What is the role of MHC molecules in relation to T cells?
What is the role of MHC molecules in relation to T cells?
What are the two types of T cells that can recognize peptide antigens presented by MHC molecules and what are their functions?
What are the two types of T cells that can recognize peptide antigens presented by MHC molecules and what are their functions?
What are the two types of MHC molecules and which T cell subsets do they present peptide antigens to?
What are the two types of MHC molecules and which T cell subsets do they present peptide antigens to?
Where are Class I MHC molecules expressed and what type of cells do they present peptide antigens to?
Where are Class I MHC molecules expressed and what type of cells do they present peptide antigens to?
Where are Class II MHC molecules expressed and what type of cells do they present peptide antigens to?
Where are Class II MHC molecules expressed and what type of cells do they present peptide antigens to?
How does the dendritic cell get prepared for T cell differentiation?
How does the dendritic cell get prepared for T cell differentiation?
How does the naive/resting CD4+ T cell proliferate into the T helper (TH0) cell?
How does the naive/resting CD4+ T cell proliferate into the T helper (TH0) cell?
What is the function of TH1 cells?
What is the function of TH1 cells?
What is the function of TH2 cells?
What is the function of TH2 cells?
What is the function of TFH cells (T follicular helper cells)?
What is the function of TFH cells (T follicular helper cells)?
How does CD8+ T cell differentiation take place?
How does CD8+ T cell differentiation take place?
What is the mechanism of killing by Cytotoxic T cells?
What is the mechanism of killing by Cytotoxic T cells?
What do Cytotoxic T cells secrete to kill infected host cells?
What do Cytotoxic T cells secrete to kill infected host cells?
What is the action of Perforin?
What is the action of Perforin?
What is the action of Granzymes?
What is the action of Granzymes?
What is the action of Granulysin?
What is the action of Granulysin?
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Study Notes
B Lymphocytes
- Crucial for the adaptive immune system, mediating humoral immune responses through antibodies produced by plasma cells.
- Defend against extracellular pathogens by producing antibodies that attack circulating pathogens in blood and lymph.
- Upon activation, B cells clonally proliferate into plasma cells or memory B cells, generating high-affinity antibodies.
T Lymphocytes
- Responsible for cellular immune responses, protect against intracellular pathogens.
- CD4+ T Cells (Helper T cells): Key regulators that send signals for cytokine production to activate other immune cells.
- CD8+ T Cells (Cytotoxic T cells): Kill virally infected cells directly.
- Mature in the thymus, developing the ability to distinguish between self and non-self, leading to destruction/inactivation of self-reactive cells.
Antibody Structure and Function
- Antibodies consist of four polypeptide chains: two light chains and two heavy chains.
- Each antibody has a unique variable region for binding specific antigens and conserved constant regions.
- B cells express 50,000 copies of a single B cell receptor (BCR) that recognizes soluble or membrane-bound antigens.
- Antibodies are found in two forms: membrane-bound (on B cell surface) and soluble (produced by plasma cells).
T Cell Receptor (TCR) Specificity
- T cells solely recognize peptide antigens; each T cell expresses thousands of a single antigen receptor.
- Unique hyper-variable region on TCRs allows binding to specific peptide antigens presented by MHC molecules.
- MHC molecules (also known as HLA) present various peptide antigens to T cells for recognition.
Antigen Presentation and Activation
- B cell activation occurs in secondary lymphoid tissue (e.g., lymph nodes, spleen) following binding of membrane-bound antibodies to antigens.
- T cells require two signals for full activation: specific antigen recognition and helper signals from other immune cells.
- Dendritic cells play a vital role in antigen presentation, maturing and loading peptides onto MHC II for T cell recognition.
Major Histocompatibility Complex (MHC)
- MHC Class I: Present on all nucleated cells, presenting antigens to CD8+ T cells.
- MHC Class II: Found solely on antigen presenting cells like dendritic cells and macrophages, presenting antigens to CD4+ T cells.
Antibody Classes
- IgM: First antibody produced during an infection, exists as a monomer on B cells and as a pentamer when secreted; functions in agglutination and complement activation.
- IgG: Most abundant antibody in plasma, involved in fetal immunity, neutralization, and complement activation.
- IgA: Second most abundant, found as a monomer in serum and a dimer in secretory fluids, plays a role in mucosal immunity.
- IgD: Least abundant; primarily involved in B cell activation.
- IgE: Least common; associated with allergic responses.
T Cell Subtypes and Functions
- Helper T Cells: Secrete cytokines (e.g., IL-2) to help activate other immune cells and stimulate B cell memory production.
- Cytotoxic T Cells: Kill infected host cells via perforin and granzymes, also can target cancer cells.
- Regulatory T Cells: Suppress autoimmune responses and maintain immune balance.
- Memory T Cells: Formed for quick response during subsequent exposures to pathogens.
Summary of Immune Defense Against Pathogens
- Phagocytes target bacteria, T lymphocytes combat viruses, and B lymphocytes produce antibodies against fungi and protozoa.
- Specific immune components interact with pathogens to elicit appropriate immune responses based on the type and characteristics of the invading organism.
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