Immuno B Cell (3/4)

• "hormones of the immune system" - TNF, IL-1, IL-6
• small proteins that serve as a way to communicate between cells
• tell the bone marrow to pump out lots of neutrophils (WBCs)
• cytokines act on the endothelium of blood vessels near infection so they become sticky --> recruit WBCs to enter the site of infection & eat bugs
• also tell hypothalamus to increase body temperature to try to kill the infection
• -INNATE IMMUNITY-

the antibody it can make (Ab=antibody)

• IgM, IgD
• if a B cell has both of these it's NAIVE (like all the 1st year MD's…)
• has not been chosen by antigen to undergo clonal expansion --> differentiation

• IgM pentamer in the serum
• @ about 4-7 days the 1st thing you see in expanding B cells are plasma cells producing IgM (in pentamer form)

• in addition, MEMORY B cells making IgG, IgA, & IgE
• over the course of an infection, cells have changed their class, but maintained antigen specificity: class switching
• you don't have to start off with a B cell that makes IgG (always start with M & D) to GET an IgG response

• underneath skin/dermis & mucosal surfaces (outlining)
• binds to mast cells and triggers release of their contents
• MAST CELLS are found skin/dermis & mucosal surfaces

• the mechanism by which lymphocytes create unique antigen-specific receptors
• T/B cell antigen receptors genes actually move and rearrange themselves within the genome of developing lymphocytes
• adaptive immune system there's a process by which you mix and match gene pieces to create the diversity of of -can partially explain autoimmune diseases

• essentially 2 choices to make: which J (joining) sequence and which V (variable) sequence will be chosen and combined with the set, inherited constant region
• one DNA rearrangement occurs
• an individual B cell will rearrange and express only one light chain using either the kappa locus or the lambda locus NEVER both
• (the variable region of an Ab's light chain is made of V & J segments)

• essentially 3 choices to make: which V (variable) sequence, which D (diversity) sequence and which J (joining) sequence will be chosen and combined with the set, inherited constant region
• TWO DNA rearrangements occur: 1st a D & J segment come together, then a V joins the already formed D-J segment, completing the heavy chain VDJ gene unit
• also there are multiple genes coding for the constant region of the heavy chain
• C region genes closest to the V region are Cμ and Cδ (IgM and IgD heavy chain constant regions)

• heavy chain:
• 50 V genes
• 20 D genes
• 6 J genes
• (don't forget there are also 9 C regions, technically 13 given IgG & IgA 'isomers')
• light chain: 40 V & 5 J genes

• 1. germline: there are multiple versions of V, (D), & J genes
• 2. combinatorial: these version can combine to form antigen specific Ab receptors (V+D+J & H+L)
• 3. junctional: imprecise joining of V, D & J regions & TdT - huge amount of diversity
• 4. SMH (somatic hypermutaiton)

• randomly adds nucleotides to cut (exonucleased) DNA regions surrounding V, D, & J genes before they're ligated together
• increases diversity in the immune system
• a rearrangement UNIQUE to B/T cells antigen receptor genes

• "survival of the fittest"
• after a B cell has been activated by an antigen, it proliferates and its antibody receptor genes undergo mutations at a rate that's orders of magnitude higher than average
• rapidly mutating variable regions of the heavy and light chains
• those that bind antigen with a higher affinity (more tightly) will be selectively chosen - can compete for the antigen much better

• two genes expressed only in developing lymphocytes required for V(D)J recombination [initial cutting of the Ig (or TCR genes)]
• w.out these genes no B or T cells are made
• SCID (severe combined immune deficiency) can be caused by defective RAG-1 or RAG-2 genes

proteins present in all cells and function in DNA repair mechanisms (incision, excision, ligation)

• cells produce antibodies with DIFFERENT heavy chain regions but MAINTAIN their variable regions
• going from IgM or IgD --> IgG, IgA, or IgE but VDJ is maintained
• cut the DNA at the switch regions (one btwn VDJ & Cμ/Cδ, the other in front of other heavy chain genes) and ligate the two together

CSR and SHM occur in germinal centers of secondary lymphoid organs (together with clonal expansion/differentiation)

• must be a MEMORY B cell
• must have gone through SMH, clonal expansion, CSR

• only B cells undergo SMH (Ab's w/ highest affinity are selected for) & CSR (class switch recombination, IgM & IgD --> IgG, A, E)
• both T & B cells use VDJ recombination though

protein that mediates BOTH class-switch recombination (CSR) & somatic hypermutation (SHM)

• RAG: VDJ recombination
• AID: CSR & SHM

• a large amount of IgM is made in order to compensate for the inability of antibodies to switch to IgG, A or E
• can be caused by a deficiency in AID protein (required for CSR & SHM)

• Pre-B: has only undergone HEAVY CHAIN VDJ recombination
• Immature B cell: after heavy chain recombination, proceeds with light chain recombination (V & J) and making the choice between kappa or lambda versions of light chains
• immature B cell: now has a complete IgM antibody (receptor) on its surface
• mature/naive B cell: IgD has a complete IgM antibody (receptor) on its surface

• markers for B cells
• lineage associated CD molecules on the surface of B cells
• CD19: appears early in B cell development
• CD20: appears later in B cell development, specifically in immature/naive & memory cells
• if a patient has a B cell leukemia, 19 and 20 will stain in a sample; used to determine if a leukemia is from a B cell progenitor (as opposed to T cell)

• passive: when you receive pre-formed antibodies
• active = a vaccination: the antiGEN is given to a person and an adaptive immune response naturally occurs to the antigen administered

• natural: maternal IgG present in newborn (from placental transfer via the neonatal FcR, Fcn)
• IgA in milk (secretory IgA)
• artificial: immunoglobulin injection of rabies immune globulin (RIG), IVIG (Intravenous immunoglobulin), or Monoclonal antibody (Mab)

• a vaccination: the antiGEN is given to a person and an adaptive immune response naturally occurs to the antigen administered
• Natural: infection with pathogen
• Artificial: immunization (eg. “killed” or “attenuated” pathogen)

3-4 weeks

• prior to birth, IgG starts to be given to the baby from the placenta at about ~3 months gestations
• at birth, the baby has ADULT LEVEL of IgG
• after birth, newborn is not making it's own antibody right immediately b/c the immune system develops slowly
• the previously maternal supply lasts for a few months while the newborn starts making its OWN IgG

• IgG is there in 1st year though & continues to climb
• IgA doesn't reach adult levels until much later (~6-8 y/o or so)

• occurs when a child's humoral immunity (usually IgG) is developmentally delayed
• present with infections at 3-6 months of age because mom's antibody has DISAPPEARED and they haven't made enough of their own
• (normal Ig levels are typically reached by 2-6 years of age in children with THI)

• arm #1: give [5] rabies vaccines (dead rabies ANTIGEN) [active]
• arm #2: give rabies immunoglobulin (ANTIBODIES from people who have been immunized against rabies) [passive]

• prepared from the pooled sera of thousands of donors 1000-10,000)
• is screened for viruses or pathogens

provides passive humoral immunity for 1) primary humoral immunodeficiency diseases & 2) children with HIV

• potentially if you dump a lot of immunoglobulins into individuals who are autoimmune to Igs, the person's plasma cells will decrease their production of Igs that are anti-self
• because there are already enough antibodies present, plasma cells slow their harmful production: feedback (mechanisms)

• 1. for diagnostics: are specific for different antigens, or PROTEINS
• 2. therapeutically: putting antibodies in people

• 1. immunized mouse with AgX (antibody)
• 2. take antibody producing spleen cells
• 3. fuse with myeloma cells - plasma cell tumor cells (will grow forever in sterile environment)
• 4. pick out HYBRIDOMAS that make Mabs to AgX

• test that uses antibodies and color change to identify a substance
• antigens from the sample are attached to a surface
• a more specific enzyme-linked antibody is applied over the surface --> binds the antigen
• a substance containing the enzyme's substrate is added
• the reaction between the enzyme & the substrate produces a detectable signal, most commonly a color change
• eg. pregnancy test uses ELISA

ONE antibody --> it will see one shape

because humans will recognize the antibodies as foreign and produce human anti-mouse antibodies (HAMA)