Which class of immunoglobulins can cross placenta:
IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells. There is evidence that IgG transfer depends on the following: (i) maternal levels of total IgG and specific antibodies, (ii) gestational age, (iii) placental integrity, (iv) IgG subclass, (v) nature of antigen, being more intense for thymus-dependent ones.
IgM
IgD
IgG
IgA
Basic Concepts