Blood and Immune [Adaptive Immunity] Flashcards
What is the B cell receptor?
A membrane bound IgM molecule associated with intracellular molecules that transmit an activation signal via phosphorylation.
What is the T Cell receptor?
TcR. An immunoglobulin like surface molecule coded for by a separate gene locus.
What are antibodies formed from?
Repeated Ig domains
What are Ig domains made of?
Two anti parallel B sheets made up of 7 constant or 9 variable B strands. The two B sheets are parallel but twisted forming a barrel. There’s a S-H bond between sheets.
Antibody Molecule structure and give the bonding
Bunny ears. 4 protein chains made of Ig domains. 2 domains in light and 4-5 heavy. L-ss-H-ss-H-ss-L. Disulfide bonds.
The Y shaped antibody has antigen binding sites at the tips of the ears.
The effector region = Fc receptors and C1.
What is IgM? Structure?
The default Ig made by all naive B cells. Membrane form is the B-cell antigen receptor (BCR). Soluable form has 10 antigen binding sites. Avidity binding with microbes. 5 Ig molecules attached in a star. 10 antigen binding sites.
Affinity
When the sun of the attractive molecular forces at two surfaces exceeds the repulsive forces. The higher the affinity, the fewer molecules it takes to associate and dissociate slowly.
Like an all blacks test match with bf.
Avidity
Results from multiple affinity contacts.
Even though the affinity of the individuals may be weak, IgM can still bind tightly to the surface of a microbe.
What are CDRs?
Complementarity Determining Regions.
The loop regions made of 3L and 3H. Contain massive amino diversity through rearrangement and imprecise joining in Ig and TcR locus.
What segment is a light chain missing?
D segment - Diversity
What are RAG1 and RAG2?
Recombination activation genes. Responsible for rearrangement of locus and are only active in B and T lymphocytes.
What is the order in which a B lymphocyte rearranges the segments? What is the acronym?
Rearranged H chain D segment to join to J segment then a V which joins to the D. The pre-mRNA formed is then spliced to a C.
Overall: D to J then V to D.
Acronym: Don’t Joke about Valid Deductive args.
Where does clonal selection take place?
Within a B cell follicle in lymph nodes
What is somatic hypermutation and when does it occur?
Affinity maturation. Hypermutation of Ig gene introducing random mutations into the rearranged VDJ genes.
Why can any antibody form complementary to anything?
The potential amino acid diversity in the antigen binding site is vast.
