Adaptive Immunity Flashcards
What are the key players in adaptive immunity?
T cells
Antigen presenting cells (dendritic cells) - These allow T cells to be affective against microbe as they capture, process and present the microbes in a way that leads to T cell activation.
What are the two differen types of mcriobes and two different responses?
Intracellular microbes = Innate. (Naive T lymphocyte interacts with antigen presenting cell.)
Extracellularly microbes = Adaptive response.
What are the features of antigen presenting cells?
- Strategic location (B and T cell interaction)
- Skin (SALT)
- Mucous membranes (GALT, NALT, BALT, GUALT)
- Lymphoid organs (Lymph nodes, spleen)
- Blood circulation (Plasmacytoid and myeloid DCs)
- Pathogen capture
- Phagocytosis (whole microbe)
- Macropinocytosis (soluble particles)
- Diversity in pathogen sensors (PRRs)
- Extracellular pathogens (bacteria)
- Intracellular pathogens (viruses)
What is the spleen?
A major organ that will fight any blood borne pathogen.
So, patients with no spleen are highly susceptible to bacteria in the blood.
What are the different types of antigen-presenting cells?
Dendritic cells - Lymph nodes, mucous membranes and blood. They present to Naive T cells.
Langerhans’ cells - Skin. They present to Naive T Cells.
Macrophages - Various tissues. They present to effector T cells.
B cells (BCR) - lymphoid tissue. They present to effector and naive T cells.
Extracellular microbes?
Activate humoral immunity. -Antibodies, complement and phagocytosis. (MHC II)
Intracellular microbes?
Cell-dependant immunity. - Cytotoxic T lymphocytes, antibodies and macrophages. Need to kill the virally infected cells (Cytotoxic T cells). (MHC I)
What are the two classes of MHC molecules?
Class I - found on all cells. Called HLA-A, HLA-B, HLA-C
Class II molecules are only expressed on antigen presenting cells (dendritic cells, macrophages and B cells) called HLA-DR, HLA-DQ, HLA-DP
What are the key features of MHC class I / II molecules?
More diverse = more effective as active against more pathogens.
Co-dominant expression - Both parental genes are expressed. This increases the number of different MHC molecules.
Polymorphic genes - Different alleles among individuals - This increases the presentation of different antigens / microbes
What are the main functions of MHC Class I / Class II?
MHC Class I = presents peptides from intracellular microbes
MHC Class II presents peptides from extracellular microbes.
What are the strctures of MHC class I / II molecules?
Peptide binding cleft - Variable region with highly polymorphic residues.
Broad specificity - Many peptides presented by the same MHC molecules.
Responsive T cells - MHC class I recognised by CD8+ T cells. MHC class II recognises by CD4+ T cells.
Antigen processing pathways
Both self and non-self peptides are presented.
All peptides from the same microbe are presented by different MHC molecules.
Susceptibility to Infection depends on the types of MHC molecules.
Endogenous pathway = Antigen peptides are loaded onto MHC I in RER after delivery via TAP (a transporter associated with antigen processing). They then present these exogenously synthesied antigens to CD8+ cytotoxic T cells.
Exogenous pathway = Antigen is loaded follwing the release if invarient chain in an acidified endosome. They then present these exogenously synthesied antigens to CD4+ helper T cells via MHC class II.
What happens in rapid HIV progressions?
HLA-B35. Homozygote in HLA-I allelels.
MHC molecules present mutated peptides (less critical peptides for the virus)
Poor recognition by T cells. Poor T cell responses.
What happens in slow HIV response?
Slow progressors = HLA-B27, HLA-B51, HLA-B57
MHC molecules present key peptides for the survival of the virus (unumtated)
Effective T cell response.
How do different MHC molecules correlate to attractiveness?
If MHC molecules are less similar then you are more attracted to a person as children will be healthier.
How do T cells respond to intracellular microbes?
How do T cell respond to extracellular microbes?
