Increased susceptibility to infection in sickle cell disease: defects of opsonization and of splenic function

Patients with sickle cell disease (SCD) have an increased susceptibility to bacterial infections and die more frequently from infection than any other cause. Their sera do not promote the phagocytosis of pneumococci normally, apparently because of an inability to utilize the alternate pathway for C3 fixation as a means of opsonization. The splenic dysfunction which exists in SCD may result in depressed synthesis of alternate pathway factor(s), as well as in decreased phagocytic clearance of bacteria.