Chapter 21 Immune System
First antibody released; potent agglutinating agent; readily fixes and activates complement
IgM
found in mucus and other secretions; prevents entry of pathogens
IgA
attached to the surface of B bells; functions as a b cell receptor
IgD
most abundant antibody found in plasma; crosses the placenta barrier
IgG
active in some allergies and parasitic infections; causes mast cells and basophils to release histamine
IgE
What do antibodies do to antigens?
inactivate and tag antigens
Name the 4 defensive mechanisms used by antibodies
1. neutralization
2. agglutination
3. precipitation
4. complement fixation
renders antigen determinants harmless
neutralization
once bound to one antigen it has the ability to bind to more than one antigen causing them to clump together
agglutination
when clumps of antigens are so large they fall out of suspension
precipitation
complement activated and attaches to any cell antibodies are attached to
complement fixation
Provide defense against intracellular antigens
T cells
CD 4 cells become ____________ when activated
helper T cells
CD8 cells become _____________ that destroy cells harboring foreign antigens
cytotoxic cells
this type of T cell helps dampen the immune response; helping against autoimmune
regulatory T Cells
describe how cytotoxic T cells destroy
perforins are small extensions from T cells that drill small hole into cells and insert granzymes and eat cells from inside out
how are immunocompetent T cells activated
when their surface receptors bind to a recognized antigen (nonself)
How are T cells activated (2 step process)
1. antigen binding
2. co - stimulation
how does antigen binding occur?
antigen presenting cells APCs present the antigen to the TCells activating the T cells
once T cells are bound to APCs what is released promoting proliferation and differentiation of activated T cells
cytokins
These cells are needed to activate an immune response
helper T cells