What are the functions of the different immunoglobulin classes?

IgM: providing immunity against extracellular polysaccharides on microbes, promoting phagocytosis and bacteriolysis, activating the complement system IgG: activates complement system, stimulating chemotaxis, facilitating phagocytosis, neonatal immunity (crossing the placenta) IgA: mucosal immunity IgE: fighting allergens and parasites IgD: initiating antibody responses