Immunoglobin

Question 1

IgG

Answer 1

• main antibody in delated response to antigen
• most abundant isotype
• fixes complement
• crosses placenta
• opsonizes bacteria
• neutralizes bacterial toxins and viruses

Question 2

IgA

Answer 2

• prevents attachment of viruses and bacteria to mucous membranes
• does not fix complement
• monomer in circulation
• dimer when secreted
• crosses epithelial cells by transcytosis
• found in secretions and early breast milk

Question 3

IgM

Answer 3

• produced in the primary immediate response to an antigen
• fixes complement but does not cross the placenta
• antigen receptor on the surface of B cells
• monomer on b cell or pentamer
• shape of pentamer allows it to efficiently trap free antigens out of tissue while humoral response evolves

Question 4

IgE

Answer 4

• binds mast cells and basophils
• cross links when exposed to allergens, mediating immediate type 1 hypersensitivity
• mediates immunity to worms by activating eosinophils
• lowest concentration in serum