Nonenzymatic glycosylation of immunoglobulin G impairs complement fixation

Transient hyperglycemia in patients receiving total parenteral nutrition may be associated with impaired immune function. The effects of short-term hyperglycemia on one aspect of antimicrobial immune function, ie, the ability of IgG to fix complement, were investigated. Aliquots of anti-human albumin, anti-horse ferritin, and anti-alkaline phosphatase were incubated for 0, 8, 16, 24, 48, and 96 hr with either 0 or 240 mg of glucose per deciliter of buffer. All samples were analyzed for the degree of glycation using a thiobarbituric acid assay, and for complement fixation ability using a microcomplement fixation assay. Significant increases in glycation over control samples were observed after only 16 hr (31 vs 15 mmol 5-hydroxymethylfurfural/mol IgG, p less than 0.01). Complement fixation was significantly altered after 48 hr of incubation (76 +/- 5% vs 90 +/- 8% total serum complement fixed by albumin/anti-albumin complex, p less than 0.03) when four of the 84 (4.7%) IgG lysine residues were glycated. It is demonstrated that a significant reduction in complement fixation by immunoglobulin occurs with elevated glucose concentrations and that this may play a clinically significant role in transiently hyperglycemic patients.     

Clinical conditions associated with positive complement fixation serology for Chlamydiae

The hospital records of 242 patients with diagnostic chlamydial complement fixation (CF) titres (seroconversion and/or titre greater than or equal to 64) found among 60,000 patients screened for suspected viral illnesses were reviewed to study the clinical conditions associated with positive CF serology for Chlamydiae. After excluding typical genital C. trachomatis infections, the majority of the remainder were considered to represent C. psittaci infections. Respiratory symptoms were the most common clinical manifestations of chlamydial infections detectable by CF, but the majority (58%) of the patients did not have pneumonia. Abdominal, neurological as well as urinary tract symptoms were common. Cutaneous, joint, cardiac, genital and ocular manifestations were also noted. Fever (greater than or equal to 38.5 degrees C) was present in 62% of the patients. The ESR was raised (greater than or equal to 20 mm/h) in the majority of the patients (83%), but the leucocyte count was usually (86%) within normal limits. Because the clinical spectrum of C. psittaci infections is apparently broad, serological tests for detecting antibodies to C. psittaci (e.g. CF) should be used widely in various clinical conditions and not for patients with pneumonia alone.