The immune response to infection Flashcards
What happens if bacteria make it past our first defences?
1) Leukocytosis : neutrophils enter blood from bone marrow
2) Margination : neutrophils cling to capillary wall
3) Diapedesis : neutrophils flatten and squeeze out of capillaries
4) Neutrophils follow chemical trail and bacteria is phagocytosed by lysosomal enzymes
What is adaptive immunity?
Antigen presentation that triggers an immune response that leads to cell-mediated immunity and antibody-mediated immunity
Immunity to pathogens is a combination of cell-mediated and antibody-mediated
What is cell-mediated immunity?
Phagocytes activated -> T cells activated
Communication and feedback to antibody-mediated immunity
Leads to attack by circulating antibodies which destroys antigens
What is antibody mediated immunity?
Activated B cells give rise to cells that produce antibodies
Communication and feedback to cell-mediated immunity
Leads to direct physical and chemical attack
What is direct physical and chemical attack?
Activated T cells find the pathogens and attack them through phagocytosis or the release of chemical toxins
Leads to destruction of antigens
Where can viral proteins enter Dendritic Cells and what happens in that region?
Phagolysosome: Phagosomal antigen will be loaded onto MHC-II for CD4 T cell stimulation
Cytosol: Cytosolic antigen will be loaded onto MHC-I for CD8 T cell stimulation
What is clonal selection?
Selective expansion of lymphocytes that interact with antigen
What is AntibodyClass (isotype) switching?
The class or isotype alters the function of the antibody
IgM —> IgG —> IgA —> IgE
Process of division, differentiation and antibody production (braindump)
Activated B cells dived and differentiate into plasma cells that secret antibody, cells that secret antibody, as well forming a seperate population of memory B cells
At the second encounter with antigen memory B cells are more numerous and are rapidly stimulated by antigen to become plasma cells
Secondary immune response are characterised by the predominance of class-switched antibodies
Stages of MHC-I loading with peptide
- Viral or bacterial infection triggers antigen presentation by MHC-I proteins
- Infection results in appearance of abnormal peptides in cytoplasm
- ER produces MHC-I proteins which the abnormal peptides are attached to
- MHC proteins with bound peptides transported to plasma membrane and are displayed
Stages of MHC-II loading with peptide
- Phagocytic APCs engulf the extracellular pathogens
- Lysosomal action produces antigenic fragments
- ER produces MHC-II protiens
- Fragments are bound to MHC-II proteins and are displayed on plasma membrane
How do antibodies bind to defined regions on a larger structure?
Antibodies bind native antigens. Several different antibodies may target a single type of microbe
Native antigen means that the antigen does not have to be processed to peptide
Antibodies can recognise just about any structure
What are isotypes of antibody?
During the immune response, B cells can genetically switch the heavy chain to change class. This does not change the antibody-specificity but does change the function of the antibody
What are adjuvants?
Adjuvants are immune stimulants added to vaccines that engage the innate system and enhance the activation of antigen presenting cells (APC)
What are examples of live attenuated vaccines?
Mumps, Measles, Rubella, Polio-Sabin
(Vaccines are administered with live microbes in very small doses that have been cultured resulting in inability to cause infection)
