Prostaglandins are a family of structurally related small lipid molecules that can regulate cellular growth, differentiation, and homeostasis. Prostaglandins are primarily derived from arachidonic acid, which is released from the membrane by phospholipases in response to a variety of extrinsic stimuli. Constitutive and inducible forms of cyclooxygenase in conceit with isomerses convert arachidonic acid into different prostaglandins including prostaglandin E₂ (PGE₂). PGE₂ was previously known as an immunosuppressive prostaglandin as it inhibits T cell production of IL-2 and B lymphocyte production of IgM. Recently a new concept emerged that PGE₂ is a critical modulator of B and T cell function and is not necessarily immunosuppressive. The focus of this paper is to present new developments that indicate PGE₂ functions by promoting antibody driven responses at the expense of inflammatory responses.