Immune System II Flashcards
Describe B cells and their antibodies
Develop in bone marrow, become plasma/memory cells, each B cell is specific for one epitope, each with unique specificity
What do plasma cells secrete and why are plasma cells different to B cells/memory cells?
Antibodies of one class/specificity of the original epitope
Plasma cells are terminally differentiated - Don’t become anything else unlike B-cells (plasma/memory cells) and memory cells (further memory/plasma cells)
Describe lymph nodes
A reticular network, made up of lymphocytes/macrophages/dendritic cells, interact with/respond to antigens
Where are lymph nodes concentrated?
Sites with lots of lymphocytes/receive fluid from peripheral tissues
What do T-cell receptors do (TCR)?
Recognise antigen fragments presented by another cell
Where are antigen fragments presented?
On MHC molecule
How do T cells produce protein IgG?
B cells/macrophages break down to form antigen presenting cells
What do T cells only recognise?
Peptides
Define an antigen
Any substance that binds specifically to an antibody/T cell receptor
What does MHC stand for and what does it do?
Major histocompatibility complex (also HLA)
Present antigens on the membrane/presentation of peptide fragments to T cells
What are the 2 classes of MHC and where can they be found?
Class I - On most cells (CD8+)
Class II - On immune cells/antigen presenting cells eg dendritic cells (CD4+)
Describe the role of MHC class I
Endogenous path - Peptide fragments bind to MHC C1 broken down to proteasome/AA sequences, transported/bind to ER at MHC C1 molecules to display on CSM, source can be intracellular infection
Describe the role of MHC class II
Exogenous - Pathogens phagocytosed into vesicles broken into peptide frags, enzymes have effect on ingested peptides to AA, associate with MHC C2 molecules for display on CSM
Describe the response of CD8+ T cells
Recognise antigen presented by MHC class I
Respond to recognition by initiating cell death
Cytotoxic T cells (TC cells)
Describe the response of CD4+ T cells
Recognise antigen presented by MHC class II
Respond to recognition by becoming activated and releasing cytokines
T helper cells (TH cells)
Describe NK cells
Many different receptors - Activator/Inhibitor
Interact with host cell
Secrete cytokines after activation and activate macrophages
What happens if the activation receptors are stimulated more than the inhibitory receptors (NK cells)?
Causes NK cells to kill the host cell
Describe what happens outside a cell when a pathogen binds to a B cells’s membrane bound antibody
Pathogen is engulfed by B cell and broken down to fragments which is attached to MHC II complex
This will bind to cell membrane to present itself (APC)
A Th Cell can bind to it with its own antigen to activate B cells
Describe what happens inside a cell if cancer cells begin to grow
MHC I complex binds to parts of the cancer cell pathogens and forms an antigen presenting cell
Tc Cells can bind to this using its antigen receptor and either activate memory Tc cells or Effector Tc Cells which can release perforins to kill the cancerous cells
What do MHC I complexes bind to?
All cells with a nucleus (except RBCs) to bind to the cells and the foreign pathogens within he cell to present it onto the cell surface
Describe the role of CD4+ cells (using Khan’s Academy video notes)
CD4+ is the alarm, only binds to MHC II complexes, dendritic cell (prof APC) will bind with the CD$+ antigen receptor
APC can become effector cells which either activate B cells or release cytokines to increase proliferation
Describe the role of CD8+ cells (using Khan’s Academy video notes)
CD8+ Th cells kill, only bind to MHC I complexes, a cancerous cell can bind to its antigen receptor to present itself
Cancerous APC can become an effector or memory cell (Tc cytotoxic killer cell) to kill the cancerous cells
