Lecture 47 Flashcards
What cells do T helper cells help activate? What do each of these cells act against?
B cells (into Plasma cells), macrophages, CD8 T cells (into cytotoxic T lymphocytes). Plasma cells: secrete different antibodies against different pathogens IgM, IgG and IgA are for extracellular microbes, IgE is for parasites and environmental antigens. Macrophages: chronic intracellular infections. Cytotoxic T lymphocytes: acute intracellular infections.
What do IgM, IgG and IgA to deal with antigens? What is weird about IgAs production?
IgM: neutralises toxins, fixes complement to the antigen, opsonisation and lysis of gram negative bacteria and virus infected cells.
IgG: fixes complement to the antigen, opsonisation and lysis of gram negative bacteria and virus infected cells. Agglutination (joining) of bacteria leading to improved phagocytodsis and neutralisation of toxins and viruses.
IgA: typically found in mucosal membranes as a dimer joined by mucosal enzymes which allow it to resist breakdown in the muscos, deals with extracellular viruses and bacteria at the mucosal surfaces. IgA is produced weirdly as it is produced in mucosal tissues (only monomeric until it passes through mucosal cells.
What type of bacteria is safe from lysis? Why?
Gram positive cells as their thick layers of peptidoglycan prevent the formation of membrane attack complexes.
What four antibody mediated mechanisms are there for antigen removal?
viral neutralisation and opsonization, agglutination of antigen bearing particles, precipitation of soluble antigens (these three enhance phagocytosis) and the activation of the complement system leading to pore (membrane attack complex formation) on cell membranes.
How does lysis work?
Pores on the cell membrane lead to influx of sodium ions and H2O due to compromisation of osmotic integrity. This leads to swelling and rupturing of the cell.
How does IgE remove parasites?
IgE which binds to mast cells and the parasites triggers the release of histamine from the mast cells, also triggers action of eosinophil which releases major basic protein (MBP) and eosinophil cationic protein (ECP) both of which are toxic to parasites.
What is gamma interferon? What type of process is this?
A cytokine released by helper T cells which activates macrophages, allowing them to destroy chronic intracellular infections within them by merging the phagosome and lysosome. This is known as cell mediated immunity.
What is the cell mediated immunity to acute intracellular infections?
This refers to the activating of CD8 T cells into cytotoxic T lymphocytes by CD4 T cells which will release perforin and granzyme from granules which will activate the apoptotic enzymes leading to apoptosis (suicide of the targeted cell) perforin forms a perforin complex which lets the granzyme in which will activate the apoptotic enzymes.
Why do we need animals to study immunity?
Immunity can’t be easily studied in the lab and must be studied in the natural environment.
