humoral immunity
cell mediated immunity
immune system response mediated by t cells and directed against parasites, fungi, intracellular viruses, and foreign tissues (grafts)
how are antibodies encoded
there are millions of antibodies with different antigen binding sites but not millions of genes antibodies are made by shuffling different domains which are encoded by genes
immunological memory
1. primary immune response to antigen A produces antibody to A 2. secondary immune response to antigen A produces antibodies to A, primary immune response to antigen B produces antibodies to B
heavy chain rearrangement
1. the variable for the heavy chain of a specific antibody is encoded by one V gene, one D gene, and one J gene; each of these genes is taken from a pool of like genes 2. the constant region is selected from another pool of genes; the number of possible combos to make an immunoglobulin heavy chain from these pools of genes is (100 V)(30 D)(6 J)(8 C) = 144,000 3. after V, D, J, C DNA segments have been joined, the resulting functional supergene is transcribed 4. splicing of the primary RNA transcript removes any introns
clonal selection steps
1. this b cell makes an antibody that binds this specific antigen 2. this binding, along with signals from TH cells, stimulates B cell to divide, resulting in clone of cells 3. primary immune response: some cells develop into plasma cells (effector B cells) that secrete same antibody as parent cell 4. potential secondary immune response: a few cells develop into non-secreting memory cells that divide at low rate, perpetuating the clone
five classes of antibodies
IgG, IgM, IgD, IgA, IgE
functions of antibodies
agglutination, precipitation neutralization, opsonization, stimulation of complement response
precipitation
antigen is no longer soluble
opsonization
binding of antibody to antigen increase likelihood of phagocytosis, not too effective against virus
agglutination
clumping antigen
IgA
dimer, saliva, tears, milk, and other body secretions, protects mucosal surfaces, prevents attachment of pathogens to epithelial cells
how Igs are encoded by genes
each of the chains of the Ig's has a constant region and a variable region the stuffing and joining of the domains occurs in embryos; heavy and light chains are chosen independently diversity is further enhanced by a high mutation rate and sloppy joining of domains DNA is lost from the maturing B-lymphocytes as the rearrangements occur; other cells don't lose this DNA only one of the two homologs undergoes rearrangement; the other is silenced this loss of DNA and silencing makes choice of antibody irreversible the constant region of the heavy chain can be altered later, changing Ig class
antigens
foreign molecules (proteins or carbs) that elicit an immune response
neutralize
interfere with antigen's function
b cells
make antibodies
IgG
monomer, free in blood plasma, 80% of circulating antibodies, most abundant antibody in primary and secondary immune responses, crosses placenta and provides passive immunization to fetus
IgD
monomer, surface of B cell, cell surface receptor of mature B cell, important in B cell activation
stimulation of complement response
not effective against virus
IgM
pentamer, surface of B cell, free in blood plasma, antigen receptor on B cell membrane, first class of antibodies released by B cells during primary response
antibody
peptides that recognize specific antigens at their specific epitopes
epitopes
regions on antigen that antibody binds to
humoral immunity
response of immune system mediated by b cells that produces circulating antibodies active against extracellular bacterial and viral infections
IgE
secreted by plasma cells in skin and tissues lining gastrointestinal and respiratory tracts, binds to mast cells and basophils to sensitize them to subsequent binding of antigen which triggers release of histamine that contributes to inflammation and some allergic responses
4 key features of adaptive immunity
specificity, distinguish self from not self, diversity, memory