COMPLEMENT ANALYSIS IN ADULT PATIENTS WITH A HISTORY OF BACTEREMIC PNEUMOCOCCAL INFECTIONS OR RECURRENT PNEUMONIA

Complement deficiencies are known to be associated with increased susc eptibility to bacterial infections. In the present study we investigat ed 80 patients with either a history of pneumococcal bacteremic infect ion, or recurrent pneumonia, or both, Hemolytic screening tests for co mplement deficiency were performed and serum concentrations of C1q, C1 s, C2, C3, C4, C4 isotypes, factor B, factor D, and properdin were det ermined, Complete deficiencies of single complement proteins were not found, 10 patients (12%) had a C4 isotype deficiency, but the frequenc y of homozygous C4A and C4B deficiency was not significantly increased , Seven patients (9%) had hypocomplementemia with low concentrations o f at least 2 complement proteins, One of these patients had profound d epletion of classical pathway components and findings suggesting acqui red C1 esterase inhibitor deficiency. 16 patients (20%) had minor comp lement aberrations. A majority of the patients with hypocomplementemia suffered from other conditions associated with pneumococcal infection s. However, impaired complement function could be a significant predis posing factor in some patients with invasive pneumococcal infections o r recurrent pneumonia.