Which type of hypersensitivity reaction involves IgM and IgG antibodies targeting cell surface antigens?

The type of hypersensitivity reaction that involves IgM and IgG antibodies targeting cell surface antigens is indeed the one characterized by the destruction or altered function of cells due to immune response. This type is classified as Type 2 hypersensitivity. In these reactions, antibodies bind to specific antigens present on the cell surface, leading to various pathological effects.

When IgM or IgG binds to cell surface antigens, it can activate complement pathways, which may result in opsonization of the cells for phagocytosis, or create membrane attack complexes that lyse target cells. This mechanism is particularly involved in conditions such as autoimmune hemolytic anemia, where red blood cells are targeted, or in certain transfusion reactions.

Type 1 hypersensitivity, in contrast, is primarily mediated by IgE antibodies and is associated with allergic reactions, such as asthma and hay fever, involving immediate hypersensitivity mechanisms. Type 3 hypersensitivity involves immune complexes that can deposit in tissues and lead to inflammation and damage, while Type 4 hypersensitivity is a delayed-type reaction mediated by T cells rather than antibodies. Therefore, the identification of Type 2 hypersensitivity accurately represents the role of IgM and IgG in targeting cell surface antigens.