Overview Flashcards
ALL blood cells develop from…
The pluripotent hematopoietic stem cell
All lymphoid cells develop from…
Common lymphoid progenitor (multipotent)
Common myeloid progenitor
Develops into granulocyte/ macrophage progenitor
Develops into megakaryocyte/ erythrocyte progenitor
Common lymphoid progenitor
Multipotentent cell produce a line of lymphoid cells
- B cells
- T cells
- NK cells
Granulocyte/ macrophage progenitor cells
Multipotent cell produced in the bone marrow that gives rise to granulocytes and monocytes
Neutrophils
Granulocyte with multilobed nucleus
- Carries out phagocytosis
Eosionophils
Granulocyte
- Levels increase in allergies
- Associated with parasitic, helminth infections
Monocytes
Myeloid cell found in the blood
- Becomes macrophages in tissues
Function
- Phagocytosis
- Antigen presentation
Dendritic cells
Myeloid cells found in the tissue (when mature)
- Undergoes antigen presentation
Basophil
Myeloid cells
- Mast cells are the tissue resident counterpart
Function not completely understood
- Increased in allergies
- Involved in helminth infections
NK
Innate lymphocytes
Function
- Direct lysis of infected cells
- Ab-dependent cellular cytotoxicity
Examples of lymphoid tissue
Payers path- small intestines
Spleen
Kidney
Lymph nodes and lymphatics
Adenoid, tonsils
Thymus
Appendix
Cytokines
Small proteins that are released from a cell and triggers a response in another cell.
Interleukins (Mainly)
Chemokines
Signalling proteins released from cells that control temporal and spatial arrangement of cells and tissue
- Similar to cytokines but with different structure
Features of innate antigen receptors
Do not recognise specific antigens
- PRR recognises PAMPs
Genome encoded
- Specific genes in the genome encode specific receptors, doesn’t change
Not clonally distributed.
Mannose binding ligand (MBL)
A Pattern recognition receptor that binds to specific spacial formation of mannose and fructose residues on plasma membrane
- Binds to the spacial formation on foreign pathogens, not host cells.
Features of adaptive antigen receptors [5]
Specificity- Recognises specific antigens
Produced by random somatic recombination of gene segments
Great receptor diversity
Clonally distributed
Memory
Antibody structure
B cell Y-shaped receptors
- Can be surface bound or secreted
- Recognises intact antigens
Contains a light and heavy chain
- Constant region (Fc)
- Variable region
- Ag binding site
T cell receptor
Surface receptor on CD4 and CD8 T cells
- Recognises processed antigens (linear peptides)
- Can only bind to peptide associated with MHC
Structure
- Alpha and beta chain
- Variable region
- Constant region connected to hinge- help by disulphide bond
- Transmembrane region
- Cytoplasmic tail
Somatic recombination
The process of producing T and B cell receptors
V and J gene segments in the light chain and V, D, J segments in the heavy chain are randomly combined
- Then spliced at the end of the constant region
Produced large receptor diversity
- Not enough space in the genome to produce as many
CD8 T cell function
Cytotoxic cell that lysis viral-infected cells.
Mehanism
- Viral proteins in the cytosol are bound to MHC I in ER
- The peptides are presented on the cell surface
- Viral peptide bound to MHC binds to T cells
CD4 T cell recognition mechanism
- Antigen taken into intracellular vesicles
- Antigens are degraded in endosomes into peptide fragments.
- Vesicles with peptides fuse with MHC II vesicles.
- MHC II presented on cell surface with pathogenic peptide
Blood vessels changes underlying inflammation
Vasodilation + increased vascular permeability
- Influx of exudates and leucocytes
Adhesion molecules
Effector mechanisms
Barriers (skin, acid pH in gut etc etc)
Cytokines
Complement
Phagocytosis (enhanced by opsonisation)
Cytotoxicity (CD8 T cell, NK cell)
Antibody-dependent cellular cytotoxicity
Mast cell and eosinophil degranulation
