Which type of antibodies are classified as warm reacting antibodies?

Warm reacting antibodies are those that are typically active at body temperature, around 37°C. Among the options provided, the antibodies associated with the Rh, Kell, Kidd, Ss, and Duffy blood group systems are classified as warm reacting antibodies. This is significant because these antibodies are primarily of the IgG class, which operates effectively at body temperature and can lead to hemolytic disease if present in sufficient quantities.

ABO and Lewis antibodies represent different types of reactions; ABO antibodies, for example, can be both warm and cold reacting depending on the specific circumstances. Similarly, P1 and MN antibodies typically react at lower temperatures, which is characteristic of cold reacting antibodies. IgM and IgG classifications indicate the immunoglobulin classes but do not directly describe their thermal reactivity or clinical relevance in terms of warm reacting antibodies specifically. Thus, the antibodies most relevant for warm reactions are found in the second choice, which encompasses those most commonly encountered in clinical transfusions and hemolytic conditions.