Erythroblastosis fetalis is an example of which type of hypersensitivity reaction?

Erythroblastosis fetalis is classified as a Type 2 hypersensitivity reaction. This condition arises when there is an incompatibility between the blood types of a mother and her fetus, most commonly when an Rh-negative mother carries an Rh-positive fetus. In this scenario, the mother's immune system can recognize the Rh-positive red blood cells of the fetus as foreign, leading to the production of IgG antibodies against these cells.

In Type 2 hypersensitivity reactions, the immune response involves antibodies binding to antigens on the surface of cells, leading to cell destruction through mechanisms such as opsonization, complement activation, or antibody-dependent cellular cytotoxicity. In the case of erythroblastosis fetalis, the binding of maternal antibodies to fetal red blood cells results in hemolysis, causing anemia and other serious complications for the fetus.

The other types of hypersensitivity reactions do not involve this specific mechanism. Type 1 hypersensitivity is associated with allergies and anaphylaxis, mediated by IgE antibodies and mast cells. Type 3 hypersensitivity involves immune complex-mediated reactions that can lead to conditions such as systemic lupus erythematosus. Type 4 hypersensitivity is delayed-type and involves T-cell mediated responses, typically seen in conditions