Immunologic studies in pneumococcal disease.

Many patients die from pneumococcal disease despite the availability of effective antimicrobial agents. Immunologic studies including detection, typing, and quantitation of serum pneumococcal capsular polysaccharide (PCP) antigen by counterimmunoelectrophoresis (CIE), quantitation of PCP antibody by radioimmunoassay (RIA), and quantitation of serum complement components C3, C4, and C3PA and serum immunoglobulins IgG, IgM, and IgA by the radial immunodiffusion technique of Mancini were performed with the sera of 18 patients. Five patients died (group I), and 13 survived (group II) pneumococcal infection. Both groups were comparable in age, underlying disease, and leukopenia on admission. All patients of group I and 10 of 13 (77%) of group II patients were bacteremic. Two patients in each group had an extrapulmonary focus infection. PCP antigen was detected in the sera of all group I and nine of 13 group II patients. PCP antigen levels were larger than or equal to 15 microng/ml in four of five group I and two of 13 group II patients (p = 0.022). Levels of antibody to PCP exceeded 100 ng/ml of antibody nitrogen (AbN) in 10 of 12 group II and one of five group I patients (p = 0.027) during the course of illness. All group I patients and three of 12 group II patients had decreased levels of one or more complement components on admission (p less than 0.01). One or more complement components remained decreased until death in four group I patients but returned to normal or elevated levels in all group II patients. No difference in serum immunoglobulin concentrations were found.