Immunology Flashcards
Name the cells part of the innate response
- Phagocytes
- Dendritic
- Eosinophil
- Basophil
- Mast cell
- Natural Killer Cell
- Complement protein
Name the adaptive response cells
- B cells
- T cells (CD4 and CD8)
Describe the main role of the innate immune system
First line of attack, it is not specific and has no memory cells so produces same response each time microbe invades
Phagocytoses and degrades foreign bodies
Describe the main role of the adaptive immune system
Highly specific immune response that has an immunological memory so releases specific antibodies if antigen returns
Initiated by innate response if attack too severe or prolonged - produces antibodies and T cells
What is self tolerance?
Immunological unresponsiveness to self-antigens
Able to do this by elimination of lymphocytes which react to self-antigens at early stages.
What are the 1st lines of defence?
- Skin
- Mucosal barrier - reproductive, respiratory and digestive tracts
- Complement in blood
What are the 2nd lines of defence?
- Lymphocytes
- Antibodies in blood
Function of Natural Killer Cells
To degrade antigens in innate immune response
Mechanism 1 of NKC
Bore holes in cell surface of target cell by secreting perforin onto them forming a membrane attack complex (MAC) and secrete enzymes that enter cell and initiate cell suicide
Mechanism 2 of NKC - activating
FasL receptors on NKC bind with Fas proteins on target cell surface and binding produces signal to induce target cell death
Mechanism 2 of NKC - inhibitory
MHC1 receptors bind MCH1 proteins target cell and do not initiate cell death as it recognises it
Inhibitory receptor dominant when present
Lack of MCH1 indicates infected cell
Process of phagocytosis
- Microbe engulfed by phagocyte - phagosome
- Phagolysosome fuses fuses and releases digestive enzyme
- Indigestible material
- Microbe broken down and excreted
Function of primary lymphoid organ
Where lymphocytes form and mature - stem cells differentiate into T/B cells (haemopoesis)
T-cell and B-cells are made in the bone marrow but B cells also mature there whereas T-cells migrate to the thymus to mature (train)
Describe POSITIVE selection in Thymus
T cells must be able to bind to MCH1 and MCH2
If cannot bind then taken to bone marrow for apoptosis
Describe NEGATIVE selection in Thymus
T cells NOT allowed to bind to MHC self-antigen and undergoes apoptosis if it does (in bone marrow)
What happens if T cells are NOT self-tolerant?
Causes autoimmunity i.e. in MS when cells attack myelin sheath around axons
Function of secondary lymphoid organs
Site of lymphocyte activation by antigens
Folicular dendritic cells (FDCs) display antigen to B cells and induce antibody production
Name secondary lymphoid organs
- Lymph node and lymphatic system
- Splee
- Toncil
What two proteins are in the antibody?
Light chain (Lc) and heavy chain (Hc)
What do you call the ‘top half’ and ‘bottom half’ of an antibody?
- Top: Antigen binding region (Fab)
- Bottom: Fc region - receptor allowing for Ig recognition
Describe T cell dependent B cell activation
Requires binding between B cell receptors (BCR) and pathogen.
Then binding of T helper cells.
Describe T cell independent B cell activation
When BCRs are clustered together by an antigen with many epitopes (Ab binding site)
Function of IgM
Fixing complement and opsonisation
Function of IgG
Opsoniser (crosses placenta)
Function of IgA
- Protects mucosal surfaces
- Resistant to stomach acid