Lecture 17- Immune System Flashcards
Phagocytes
destroy pathogens by engulfing them, acidifying the phagolysosome and digesting the contents.
When phagocytes cannot ingest their targets, they may release chemicals that are lethal to pathoge
Natural killer cells
function like T lymphocytes but are part of innate immunity.
They lyse and kill cancer cells and virus-infected cells before the adaptive immune response is activated.
Inflammation
Occurs when body tissues are injured
Limits the spread of damage, disposes of debris and pathogens, alerts the adaptive immune system, and sets up repair.
four main signs of acute inflammation are:
redness
heat
swelling
pain.
Pro inflammatory chemicals
Causes vasodilation and increased capillary permeability
Allows fluid containing clotting factors and antibodies to enter the tissues followed by neutrophils and macrophages
Antimicrobial proteins
Enhance innate defences by attacking microorganisms directly or by hindering their ability to reproduce
Interferons (IFNs)
small proteins produces by virus infected cells that help protect surrounding heathy cells by telling the tot make proteins that interfere with viral replication
Complement cascade
Group of plasma proteins that Can assemble a membrane attack complex to kill a cell by punching a hole int he plasma membrane, making the cell leak
Microbe associated molecular patterns
Often indicate something is trying to infect yo
Adaptive defences
Recognize and destroy the specific antigen that initiated the response
What does Adaptive immune response include?
Systemic response
Has memory
Includes both cellular immunity and humoral immunity
Cellular immunity
Based on direct attack of microorganisms by T lymphocytes and has living cells as its protective factor
Humoral immunity
Provided by antibodies present int he body’s “humours” or fluids produced by B lymphocytes
Antibodies are proteins that target and bind to extracellular antigens.
Clonal expansion ( mitosis) develops clones into plasma cells and the remaining cells into memory B cells.
Clonal selection
Antigen binding with a particular lymphocyte selects that lymphocyte for further development
Colonal expansion
producing a group of cells with an identical ability to bind this antigen.
Effector cells
actively fight the infection.
Memory cells
Respond quickly to future encounters with this antigen
Antigen presenting cells (APCs)
phagocytose pathogens and present antigen fragments in major histocompatibility complex II (MHC II) molecules on their surfaces, where they can activate T cells.
Dendritic cells
Located near external body surfaces (skin) phagocytose antigens and migrate to lymphoid organs to present antigens to T cells
Macrophages
Found in lymphoid organs and connective tissues and present antigens to T cells
B lymphocytes
Present antigens to T cells in order to become more fully activates B cells
What are the two major groups of T cells based on cluster of differentiation?
CD4+ cells
CD8+ cells
CD4+ cells
Helper T cells that activate B cells, T cells and macrophages, some are regulatory T cells hat inhibit overly aggressive responses
Activated by Class II MHC ( 2 X 4 = 8)
CD8+ cells
Cytotoxic T lymphocytes that destroy cells or foreign substances
Activated by Class I MHC ( 1 X 8 = 8)
Class I MHCs
found on all body cells except RBCs and display antigens synthesized from within the cell
if infected, may also include fragments of foreign antigens.
If cells mutate so they no longer produce MHC I, they will be destroyed by NK cells.
Class II MHCs
only on antigen-presenting cells (dendritic cells, macrophages and B cells) and display antigen fragments from phagocytosis.
Helper T cells
TH1cells- work with macrophages and CD8+ cytotoxic T lymphocytes to activate cell-mediated immune responses against intracellular threats.
TH2 cells- work with B cells, eosinophils and mast cells to stimulate B cell proliferation and increase antibody production against extracellular threats.
What are the ways antibodies help fight off infection?
Neutralization
Opsonization
Complement fixation and activation
Neutralization
occurs when antibodies block specific sites on viruses or toxins, causing them to lose their infectious or toxic effects.
Opsonization
occurs when antibodies stick to antigens and make it easier for phagocytes to engulf pathogens.
Complement fixation and activation
occur when complement proteins bind to antibodies attached to antigens and lead to lysis of the cell.
Primary immune response
occurs on first exposure to a particular antigen, with a lag time of about 3-6 days.
The antibody titre in the blood rises, peaking in about 10 days, and then declines.
Secondary immune response
occurs when someone is exposed to the same antigen for a second time.
Mobilization of B cells takes only a few hours and rises to a much higher peak concentration after only 2-3 days, producing antibodies with a higher binding affinity for the antigen, and can persist for weeks or months.
