3.2.4 Cell recognition and immunity Flashcards
What is an antigen?
A molecule, usually a protein, that triggers an immune response when recognized as foreign by the immune system.
What is the role of antigens in the immune response?
Antigens are used by the immune system to identify pathogens, abnormal body cells, toxins, and non-self material (e.g., cells from other organisms).
What are the main types of white blood cells involved in the immune response?
Phagocytes: Engulf and digest pathogens.
T lymphocytes (T cells): Involved in cell-mediated immunity.
B lymphocytes (B cells): Involved in humoral immunity by producing antibodies.
What are self and non-self cells?
Self cells are the body’s own cells, while non-self cells are foreign and trigger an immune response.
What is the difference between specific and non-specific immune responses?
Non-specific: Immediate and general defense (e.g., phagocytosis, inflammation).
Specific: Slower but targets specific antigens (e.g., T and B cells).
Describe the role of lysosomes in the immune response.
Lysosomes contain enzymes (e.g., lysozymes) that digest pathogens after phagocytosis.
What is the role of inflammation in the non-specific immune response?
Inflammation increases blood flow to the affected area, bringing more white blood cells and antimicrobial proteins to fight infection.
What is phagocytosis?
The process where phagocytes engulf and digest pathogens.
Describe the stages of phagocytosis.
Pathogen is recognized and binds to receptors on the phagocyte.
The pathogen is engulfed into a vesicle called a phagosome.
The phagosome fuses with a lysosome to form a phagolysosome.
Enzymes digest the pathogen.
The phagocyte presents the pathogen’s antigens on its surface (antigen presentation).
What are T cells, and where are they produced?
T cells are lymphocytes involved in the cell-mediated immune response. They are produced in the bone marrow and mature in the thymus.
What is the role of helper T cells (TH cells)?
Helper T cells:
Release cytokines to activate B cells, cytotoxic T cells, and phagocytes.
Stimulate clonal expansion of B and T cells.
What is the role of cytotoxic T cells (TC cells)?
Destroy infected cells by releasing perforins, which create pores in the cell membrane, causing cell lysis.
What is the process of clonal selection and clonal expansion?
Clonal selection involves identifying the specific lymphocyte that matches the antigen. Clonal expansion is the rapid mitotic division of this lymphocyte to produce a large population of identical cells.
What are B cells, and where are they produced?
B cells are lymphocytes involved in the humoral immune response. They are produced and mature in the bone marrow.
What is the role of plasma cells?
Plasma cells are activated B cells that secrete specific antibodies to fight pathogens.
What are memory cells, and why are they important?
Memory cells are long-lived B or T cells that remain after an infection, allowing a faster and stronger secondary immune response if the same antigen is encountered again.
What are the four main ways antibodies work?
Agglutination: Clumping pathogens together for easier phagocytosis.
Neutralization: Blocking toxins or preventing pathogens from binding to cells.
Opsonization: Marking pathogens for phagocytosis.
Activation of complement: Triggering a cascade that leads to pathogen lysis.
What is the difference between the primary and secondary immune responses?
Primary response: Slow and produces fewer antibodies; occurs during the first exposure to an antigen.
Secondary response: Faster and stronger due to memory cells.
What is a vaccine, and how does it work?
A vaccine contains antigens from a pathogen (weakened or inactivated) that stimulate the production of memory cells without causing disease.
What is the difference between active and passive immunity?
Active immunity: Produced by the individual’s immune system (e.g., vaccination or natural infection).
Passive immunity: Antibodies are provided from an external source (e.g., maternal antibodies or antibody injection).
What are the advantages and disadvantages of active and passive immunity?
Active immunity: Long-lasting but slower to develop.
Passive immunity: Immediate but short-term.
What are monoclonal antibodies?
Identical antibodies produced from a single B cell clone, specific to one antigen.
Give two uses of monoclonal antibodies in medicine.
Cancer treatment: Delivering drugs to specific cancer cells.
Diagnostic tests: Detecting specific antigens (e.g., in pregnancy tests).
What are the ethical issues surrounding monoclonal antibody use?
Use of animals in antibody production, potential side effects, and accessibility concerns.
What is antigenic variability, and how does it affect immunity?
Antigenic variability occurs when pathogens change their surface antigens. It makes them harder to recognize, leading to recurring infections and reducing vaccine effectiveness (e.g., flu virus).
Why is antigenic variability common in RNA viruses?
RNA viruses lack proofreading enzymes during replication, leading to frequent mutations.
What is an autoimmune disease?
A condition where the immune system mistakenly attacks the body’s own cells (e.g., rheumatoid arthritis, type 1 diabetes).
How do autoimmune diseases arise?
failure of self-recognition mechanisms, leading to an immune response against self-antigens.
How can you test for the presence of a specific antigen in a sample?
Using the ELISA test (enzyme-linked immunosorbent assay).
Describe the steps of an ELISA test.
Antigen is bound to a surface.
Add specific antibodies that bind to the antigen.
Add a second antibody with an enzyme attached.
Add substrate for the enzyme, causing a color change if antigen is present.
What is the importance of controls in an ELISA test?
To ensure the results are valid by confirming that the observed effects are due to the antigen-antibody reaction.
What does a graph of antibody concentration vs. time show during primary and secondary immune responses?
The secondary response shows a faster and larger increase in antibody concentration compared to the primary response
How can data from vaccination programs be used to evaluate effectiveness?
By comparing infection rates before and after the introduction of a vaccine and analyzing herd immunity effects.
What does the term “herd immunity” mean?
When a large proportion of the population is immune, reducing the spread of a pathogen and protecting individuals who are not immune.
