Immunology review Flashcards
Complete this flow diagram summarising the different immunological pathways
Label the cells and their role in an immunological response
What is the purpose of the complement system?
a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism.
Causes stimulation of phagocytes to clear foreign and damaged material, inflammation to attract additional phagocytes, and activation of the cell-killing membrane attack complex
Describe the activation of the complement system
Although part of the innate immune system, it can be recruited and brought into action by antibodies generated by the adaptive immune system.
Where are complement proteins synthesised?
Liver - circulate in blood as inactive precursors
What triggers the activation of the complement system?
Antigen-antibody complexes
Cytokines
Pathogen recognition
What are the 3 pathways that activate the complement system?
Classical Pathway – via antigen-antibody complexes
Lectin Pathway – via mannose-binding lectin
Alternative Pathway – via direct pathogen detection
What happens when C3 is activated?
C3a – Recruits neutrophils & monocytes (inflammation)
C3b – Opsonisation (marks pathogens for phagocytosis), amplifies cascade & activates C5
What is the function of C5 activation?
C5a – Potent inflammatory signal, attracts immune cells.
C5b – Initiates Membrane Attack Complex (MAC)
What is the membrane attack complex (MAC)?
Protein structure that punches holes in pathogen cell membranes, leading to cell lysis and death
Label the structures of the lymphatic system
Identify these WBCs and describe their function
Describe the process of humoral adaptive immunity
Humoral adaptive immunity is antibody-mediated immune response
- Antigen Presentation: Antigen-presenting cells (APCs) process pathogen antigens & display them on MHC II receptors
- T Helper 2 (Th2) Activation: Th2 cells bind to MHC II-antigen complex & release cytokines
- B Cell Differentiation: Cytokines stimulate naïve B cells to undergo class switching & express antigen-specific B cell receptors
- Plasma & Memory Cells:
- Plasma cells produce pathogen-specific antibodies
- Memory B cells store antigen information for faster future responses
Unlike humoral immunity, cell-mediated immunity doesn’t involve antibodies. Instead, it targets infected or abnormal cells (intracellular pathogens) through cytotoxic T lymphocytes (CD8+ T cells) & cytokines
1.CD8+ Cytotoxic T Cell Activation:
- CD8+ T cells recognise infected or apoptotic cells by binding their T cell receptor (TCR) to MHC Class I receptor presenting pathogenic antigen
- Cell Destruction:
Upon binding, CD8+ T cells release cytokines & granules that induce apoptosis in infected cell - T Helper 1 (Th1) Role:
Th1 cells bind to dendritic cells, which further recruit & activate CD8+ T cells to enhance immune response
What is the role of each of these antibodies?
How do antibodies recognise and bind to antigens?
Antibodies recognise specific epitopes on antigen using their variable regions
Epitope is precise part of antigen that fits into binding site of antibody.
If antigen doesn’t have correct epitope, antibody will not bind
This specificity is crucial for immune system targeting & neutralisation of pathogens
What are the different roles of antibodies in the immune response?
Neutralisation – Block pathogens & toxins from binding to cells.
Opsonisation – Coat microbes to enhance phagocytosis by immune cells.
Antibody-Dependent Cellular Cytotoxicity (ADCC) – Mark infected cells for destruction by Natural Killer (NK) cells
Lysis of Microbes – Trigger complement activation to break down pathogens
Complement Activation – Leads to phagocytosis, microbe lysis & inflammation
Inflammation – Recruits immune cells like neutrophils to site of infection
How does immunological memory enhance the immune response upon reinfection?
First Infection → Triggers primary immune response, leading to formation of B memory cells
Inapparent Reinfection → Memory B cells respond quickly, producing faster & stronger antibody response
Long-Term Immunity → Years later, mild or inapparent reinfection results in enhanced immune response, preventing severe disease
What is each antibody involved in and what is their location?
What is an ELISA and what is it used for?
Enzyme-linked Immunosorbent Assay
Common immunoassay used to detect & measure specific analytes (e.g. antibodies) in sample
Frequently used in diagnostics to determine whether antibodies have been produced in response to pathogen exposure or vaccination
How does an ELISA test function?
- Antigen Immobilisation – Antigen is attached to microtiter plate either by adsorption or via capture antibody
- Antibody Binding – Detection antibody binds to antigen, forming antigen-antibody complex
- Detection – The detection antibody is either:
- Directly conjugated to enzyme (e.g. Horseradish Peroxidase (HRP))
- Bound to labeled secondary antibody (depending on ELISA type) - Colour Change Reaction – Enzyme catalyses reaction, producing measurable colour change, indicating presence of target analyte
