Immunology - Antibodies (Immunoglobulins)
*Immunoglobulins = Antibodies
- 5 subtypes
- GAMED
Immunoglobulin *Structure
- light chain and are constant
- heavy chain is variable = G A M E D
- variable ends on both the light and heavy chains
--> where the Fab is located, Fab = fragment antigen binding site
--> note the variable end can be present on any of the 5 types
Compliment and Phagocytic Attachment Sites
- FAGS don't Fc their compliment
Compliment binding site on Immunoglobulins
Notes:
- the Ci compliment binds to the Fc portion of the antibody on ONLY IgM and IgG
--> recall these are the only 2 antibodies that can activate the compliment system
example:
Heavy Chain
- defines the 5 subtypes of antibodies
- coded for by different exons and mRNA splicing
5 Immunoglobulins
*IgG
- IgG is the major opsonin
--> helps phagocytes eat bacteria
Notes:
- both IgM and IgG are first responders to any pathogen and good activators of the complement system
--> IgM since it is the first antibody present on B cells before class switching
--> IgG since it is the most abundant antibody in the serum - IgM valence = 2
- IgG only antibody that can cross the placenta barrier
--> IgG gives neonates immunity for first 6 months of life
*IgM
- IgM "makes" all other antibodies
Notes:
- both IgM and IgG are first responders to any pathogen
--> IgM since it is the first antibody present on B cells before class switching
--> IgG since it is the most abundant antibody in the serum - IgM as B Cell receptor
--> valence = 2 - IgM as in serum = pentamer
--> valence = 10
*IgD
- IgD tells B cells they are "DONE" maturing in bone marrow
Notes:
- IgD valence = 2
- very low serum count
- IgD exist with IgM on the Bcells as B cell receptors when they are in the bone marrow
- IgD cells tell the B cells they are "DONE" maturing and to leave the bone marrow
- think of IgD = B cell driver's liscence
--> once they express IgD they can leave the bone marrow and DRIVE around the body's lymphatic system
--> they are amture at this point, but NAIVE
*IgA
- IgA "Airways and mucosA surface Area"
- IgA dimer transport through enterocytes to GI lumen mucosa
Notes:
- IgA valence = 2
- in serum forms dimers --> valence = 4
- since IgA is important for surface Area mucosa and airway immunity against infection
- babies have IgG from mother for first 6 months through placenta transport
- but babies need respiratory protection
--> they get IgA from mother's breast milk
--> protection fro RTIs
IgA deficiency
- body either doesn't produce IgA or build IgE antibodies against your own IgA
Notes:
- note that IgA deficient patients can react to blood transfusions since there is a possibility IgA to be in blood
IgA migration through enterocytes to gut lumen
- IgA GI enterocyte transport requires 2 things
--> J CHAIN and SECRETORY component - J CHAIN = needed to form the IgA dimer
- SECRETORY component = needed in the cytosol and lumen to stop our body from breaking it down
*IgE
- IgE = "Elergic reactions"
Notes:
- IgE valence = 2
- in serum very low amount, mostly are attached firmly to granulocytes by Fc receptors
- granulocytes
--> mast cells
--> basophils
--> eosinophils - IgE good for complex pathogens like parasites and worms
- also for ELlergic reactions
2 Functions of IgE
- Ellergic Reactions
--> antibody mediated degranulation - Parasitic cell-mediated cytotoxicity
IgE Parasitic cell-mediated cytotoxicity example
Case presentation:
Notes:
- note that
B cell Receptors
- are essentially antibodies attached to B cells with a transmembrane part to them
- their variable region is called the Fab region
- Fab = fragment antigen binding
--> think that only FRAGMENTS of antigen are needed to BIND
--> Valence refers to the amount of Fab or binding availability different antibodies have - As B cells mature they release their B cell receptors as antibodies
Gamma Immunoglubulins
- note that globulins in general as a protein class can be grouped by their molecular weight by gel electro
- GAM of immunoglobulins are gamma globulins
*DIRTY USMLE
antibodies
