Which immunoglobulin is most likely responsible for hyperacute rejection after a donor kidney transplantation?

In the context of hyperacute rejection following donor kidney transplantation, IgG is the main immunoglobulin involved. This type of rejection occurs within minutes to hours after transplantation and is primarily mediated by pre-existing antibodies against donor antigens, specifically those present on the endothelial cells of the transplanted organ.

In many cases, the recipient may have been sensitized to the donor's HLA (human leukocyte antigen) antigens through previous transplants, blood transfusions, or pregnancies. When a kidney is transplanted, these pre-formed IgG antibodies bind to the donor's vascular endothelium, leading to complement activation, neutrophil recruitment, and rapid destruction of the graft.

The involvement of IgG is significant because it is the most abundant immunoglobulin in serum and is known for its ability to cross the placenta and activate the complement system effectively. This makes it particularly potent in mediating immediate hypersensitivity reactions, such as hyperacute rejection.

In contrast, IgA is primarily found in mucosal areas and body secretions, IgD is mainly found on the surface of B cells and plays a role in B cell activation, and IgE is associated with allergic reactions and responses to parasitic infections. None of these other antibodies typically participate