Lecture 9 - Adaptive Immune Response (Recognition) Flashcards
What does the suffix -mab mean?
Monoclonal antibody
What is a pathogen?
Any microorganisms that can cause disease in humans?
What is a Naive T cell?
T cells that have not yet encountered the antigen of a pathogen
What is the only cell that can activate T cells?
APCs (Antigen presenting cells)
How do APCs give information to T cells?
Sense the pathogen
Capture the pathogen
Process the pathogen
Present the pathogens antigen to T cells
What are the 4 different APCs?
Dendritic cells
Langerhans cells
Macrophages
B cells
What is the similarity between Dendritic cells and Langerhans cells?
Langerhans are just Dendritic cells that are present in the skin
What do dendritic cells and langerhans cells present antigens/pathogens to?
Naive T cells
What cells do Macrophages and B cells present pathogens/antigens to?
Effector T cells
What is the function of Dendritic cells and langerhans cells presenting pathogens to Naive T cells?
To stimulate T cell response against most pathogens
What is the T cell response?
T helper cells (help B cells)
Cytotoxic T cells
What is the function of Macrophages presenting pathogens to Effector T cells?
Produce cytokines which promotes phagocytise activities
What is the function of B cells presenting pathogens to effector (helper) T cells?
To stimulate the Antibody response (Humoral response)
Aim to produce the best antibody IgG
What are effector T cells?
T cells that have previously encountered the antigen and are capable of performing effector functions during an immune response
What is the largest lymphoid organ in the body?
Spleen
What are the 3 key features of APCs?
Strategic location
Diversity in pathogen capture mechanism (Phagocytosis + macropinocytosis)
Diversity in pathogen sensors (PRRs)
What do the PRRs of APCs bind to on pathogens?
PAMPs
What type of receptors are often PRRs to detect pathogens?
Toll like receptors
Where can toll like receptors be found?
On plasma membrane of the cell (extracellular pathogen detection)
Nuclear membrane (intracellular pathogen detection)
What toll like receptor typically binds to Staphylococcus aureus?
TLR2
Since it’s Gram +ve
What pathogen associated molecules bind to TLR4?
Lipopolysaccharides
E.g made by Neisseria meningitidis or E.coli
Gram Negative
What does binding of endotoxins (Lipopolysaccharides) to TLR4 activate?
Innate immunity
Inflammatory response
What happens to the APCs once its captured and processed the pathogen?
Migrates to lymphoid tissue to activate the maximum amount of T and B cells as possible
What are a few examples of lymphoid tissues?
GALT (In Gut)
BALT (In Bronchioles of lungs)
SALT (In Skin)
Lymph nodes
Spleen
What happens to the APCs once they’ve migrated to the lymphoid tissue?
Present antigens to correct T cells that lead to the best adaptive immune response
What adaptive immune response is stimulated when exposed to extracellular microbes?
Humoral Immunity (Antibody production)
What adaptive immune response is stimulated when exposed to intracellular microbes?
Cell mediated immunity (Cytotoxic T cell response)
What is the function of Cytotoxic T cells?
Destroys infected cells
(E.g cells infected by a virus)
What do Intracellular microbes usually produce that stimulate natural killer cells?
Interferons
What is the importance of APCs?
In infection by Intracellular or extracellular they present pathogens to Naive T cells activating the best immune response (Humoral immunity or cell mediated immunity)
How are pathogens presented to naive T cells?
Via MHCs (Major Histocompatibility Complex) also called HLA (Human Leukocyte Antigen)
MHC = HLA
What are the 2 types of MHC molecules?
MHC Class I
MCH Class II
What cells express MHC Class I molecules?
ALL Nucleated cells
What cells express MHC Class II molecules?
Antigen-presenting cells (Dendritic cells, macrophages and B cells)
What class of MHC molecules do Dendritic cells have?
Both MHC Class I and Class II
Is both a nucleated cell and an antigen presenting cell
What class of MHC molecules do red blood cells have?
Neither since they are not nucleated (no Class I) or Antigen presenting cells (no Class II)
What type of microbes, (intracellular or extracellular) are always presented by MHC Class I molecules?
Intracellular microbes
What type of microbes, (intracellular or extracellular) are always presented by MHC Class II molecules?
Extracellular microbes
What is the advantage of their being different alleles for MHC molecule production?
Means different people can respond to different microbes
What T cells will recognise MHC Class I molecules?
CD8 positive T cells
What T cells will recognise MHC Class II molecules?
CD4 positive T cells
When invaded by extracellular microbes, what class of MHC molecule on the APC presents it to the Naive T cell?
What molecules will these T cells have?
MHC Class II
CD4 positive Naive T cells
When invaded by intracellular microbes, what class of MHC molecule on the APC presents it to the Naive T cell?
What molecules will these T cells have?
MHC Class I molecules
CD8 positive Naive T cells
What Naive T cells are responsible for triggering Cell-mediated/cytotoxic T cell response?
CD8+ T cells
What is the exogenous pathway/processing of extracellular microbes?
Microbes captured via phagocytosis or macropiniocytosis
Degraded in endosome
Vesicle containing MHC Class II complex fuses witht endosome
APCs present these antigens to CD4+ T cells
What is the endogenous pathway/processing of intracellular microbes?
Viral protein in the cytosol
Proteasome marks it for destruction
Broken down antigenic peptide transported to the ER
Peptide exposed to MHC Class I
Complex displays the viral antigen to CD8+ T cells
Why is it good that there is genetic polymorphism for MHC molecules?
No 2 individuals have same set of MHC molecules so a single microbe is unlikely to wipe everybody out
More diversity of MHC molecules means more likely to develop immunity to a disease
If a patient with HIV has low CD4+ T cell count and a high viral load, what treatment would you do?
Anti-retro viral Therapy
If a patient with HIV had a High CD4+ T cell count and a low viral load, what would you do?
Nothing
Why is it important that the HLA molecules (MHC) between an organ donor and recipient match?
Rejection
What autoimmune diseases are associated with the presence of certain HLA molecules?
Ankylosis spondylitis
Insuli-dependant Diabetes Mellitus
SLE (Systemic Lupus Erythromatosus)
Is a patient more or less susceptible to suffering to an infection if they have a low MHC molecule diversity?
More susceptible
