Opsonization of pneumococci by whole serum from sickle cell disease patients

An in vitro opsonic activity test was developed to measure the ability of whole serum from sickle cell disease patients to enhance the phagocytosis of Streptococcus pneumoniae by normal white blood cells. At the 30- and 60-minute incubation time periods, there was a 2- to 3-log reduction in the number of colonyforming units of S pneumoniae with both normal and sickle cell serum indicating opsonization of the organisms. However, the reduction in colony-forming units was significantly greater with normal than with sickle cell serum at both time periods (P <.0005 and P <.025 for the 30- and 60-minute time intervals, respectively). The sickle cell sera used in this assay were obtained from pediatric patients (age range, 1 to 15 years) and from adults (age range, 16 to 30 years). Based on this assay, sera from the adult sickle cell patients had a lower mean opsonic activity than that of the pediatric group. The significance of the lower opsonic activity in the adults with sickle cell disease is unknown and requires additional investigation.