32 Immunogenetics Flashcards
antibodies produced by B cells
humoral immunity
action of T cell receptors
cellular immunity
B cells mature in…
the bone marrow
B cells produce
antibodies
T cells migrate to
the thymus where they mature
Each B cell is specific for…
one antigen
Steps of B cell immune response
- detection of foreign antigen
- activation of immune cells
- some cells differentiate into plasma cells that produce antibodies specific to antigen
- after threat is gone, primary immune response shuts down, leaving behind memory cells
secondary response
an antigen comes back a second time
the remaining memory cells from the first response rapidly bind to the antigen giving rise to more plasma cells producing more antibodies
Structure of an antibody
4 protein chains - 2 heavy and 2 light held together by disulfide bonds
each chain has a constant region, a joining region, and a variable region
the antigen binds the ___ of an antibody
variable region
types of antibodies
IgM IgG IgA IgE IgD
The light chain is either…based on…
kappa or lambda
the constant region present
Variation in antibodies due to…
- somatic recombination
- alternative sites for recombination
- somatic mutations
somatic recombination
- occurs in B-cells during B cell differentiation
- allows various combinations of constant, joining, and variable regions to be combined
- the germ line DNA contains many options and during maturation the antibody producing genes in each B cell is processed slightly differently
mutation rate in B cells
~2% or 1 in 50
compared to 1 in 100,000 in non-antibody genes
describe somatic recombination
as the B cell matures, a variable region and joining region are positioned adjacent to each other
junctional diversity means that the processing in this cell will be slightly different in different cells with the same two segment together
transcription and processing occur
allele exclusion
there are 2 copies of each chromosome
if one allele produces an antibody that recognizes an antigen, the other allele will not be used to produce an antibody
Bruton’s Disease
X-linked recessive
B cells and plasma cells missing or nonfunctional so no antibodies are made
T cells are ok, protect against viruses
Therapy for Bruton’s disease
bone marrow transplant to give new stem cell population to give rise to functional B cells.
agammaglobulemia
Bruton’s disease
SCID
Severe combined immunodeficiency syndrome
Autosomal and X-linked forms - may be due to interaction of many genes
Both B and T are nonfunctional
ADA
adenosine deaminase
missing in one form of SCID
treatment for ADA lacking SCID
treated by transferring good ADA gene to white blood cells with retrovirus
cells with active ADA gene are put into patient in hopes that the enzyme will stimulate T and B cell activity
