Immunoglobulins Flashcards
TCR
T cell receptor on the surface of T cells
Responsible for recognizing fragment of antigen as peptides bound to MHC molecules
CD4`
Glycoprotein and co-receptor for the TCR
Found on helper cells, monocytes, macrophages and dendritic cells
CD8
Transmembrane glycoprotein and co-receptor for TCR
T cell signaling and aiding with cytotoxic T cell antigen interactions
What are the functions of antibodies in infection?
Toxin neutralization
Microbial binding (prevents attachment, neutralization)
Cytotoxicity against virus-infected cells
Opsonization (phagocytosis)
Complement fixation (lysis)
Mast cell degranulation
IgM
First antibody formed in the newborn vertebrate
First and major Ig in the primary immune response
Second highest in serum concentration
What is the structure of IgM?
Molecular weight: 900,000 daltons
In pentameric form of 5 subunits held together by a J chain
What is IgM efficient in?
Intravascular, complement activation, opsonization, agglutination and virus neutralization
IgG
In serum formed in secondary responses
Can opsonize, agglutinate and precipitate antigen
When does IgG appear?
In increased amounts of sera after an initial lag on the first immunization
IgA
Minor component in serum
Major Ig in external secretions in non ruminants (IgG1)
IgA structure
Common form is dimer of 2 identical units joined by J chain
IgA function
Protects mucosal surfaces, mammary glands and eyes
Doesn’t activate complement and not an opsonin, intravascular and secretions
What happens when IgA is secreted by a plasma cell?
In mucosa it’ll bind to a receptor on epithelial cells
Turns into secretory IgA (sIgA)
What is the function of secretory component of IgA
Protects IgA against proteolytic enzymes (degradation)
Facilitates transport of sIgA into secretions
IgE
Mediates type 1 hypersensitivity
Binds to mast cells and basophils
With antigen, mediates release of vasoactive amines (histamine, serotonin)
When is IgE important?
Anti-parasitic immunity
When does IgE increase?
Atopic skin diseases (eczema)
Hay fever
Asthma, anaphylactic shock, IgE-myeloma
IgD
Found on the membrane of B lymphocytes
Sensitive to proteolytic enzymes
Low serum concentration
What is the role of IgD?
May serve as an antigen receptor
Plays a role in antigen-triggered clonal proliferation
Immunoglobin isotopes in chickens?
IgM, IgA and IgY produced in the bursa of fabricus
What animals have IgG, IgM, IgD and IgA?
Mice (bone marrow)
Rabbits (appendix)
Sheep (peyer’s patches)
Horse
What species has only IgG, IgM and IgE?
Cattle
What do immunoglobulins do in mothers?
In colostrum and breastmilk, protein that allows mother to pass immunity to her baby
Which immunoglobulins do mothers have?
IgA, IgM, IgG
sIgM and SIgA
