Drug-Induced Cytotoxic Reactions

Figure 2 Hemolytic disease of the newborn.

HDNB is usually prevented today by passive immunization of the Rh - mother at the time of delivery of any Rh + infant with anti-Rh antibodies, which are available commercially. These anti-Rh antibodies combine with any fetal Rh+ RBCs that have entered the mother's circulation, so it is much less likely that she will become sensitized to the Rh antigen. If the disease is not prevented, the newborn's Rh + blood, contaminated with maternal antibodies, may have to be replaced by transfusion of uncontaminated blood.

Blood platelets (thrombocytes) are minute cell-like bodies that are destroyed by drug-induced cytotoxic reactions in the disease called thrombocytopenic purpura. The drug molecules are usually haptens because they are too small to be antigenic by themselves; but when a platelet has become coated with molecules of a drug (quinine is a familiar example), and the combination is antigenic (Figure 3). Both antibody and complement are needed for lysis of the platelet. Because platelets are necessary for blood clotting, their loss results in hemorrhages that appear on the skin as purple spots (purpura).

Figure 3 Drug-induced thrombocytopenic purpura. Molecules of a drug such as quinine accumulate on the surface of a platelet and stimulate an immune response that destroy the platelet.

Дата добавления: 2015-06-04