[Immunocomplexes in pediatrics. I: Detection with polyethilenglycol precipitation (author's transl)]

Area of Science:

• Immunology
• Clinical Chemistry

Background:

• Circulating immune complexes (CICs) have variable clinical significance, ranging from protective mechanisms against chronic antigenemia to mediators of tissue injury, such as in glomerulonephritis.
• Detecting CICs is challenging due to their heterogeneity, necessitating diverse analytical methods.

Purpose of the Study:

• To evaluate the polyethylene-glycol (PEG) precipitation test for detecting circulating immune complexes.
• To compare the PEG precipitation test with other established methods, including C'1q, Fc, and C'3b receptor binding assays and physical separation techniques.

Main Methods:

• The study utilized polyethylene-glycol precipitation with varying concentrations of albumin-antialbumin complexes.
• Sera were subjected to heat treatment (60°C for 30 minutes) and repeated freezing and thawing cycles.
• Optical density measurements were used to quantify precipitate levels.

Main Results:

• Heating sera to 60°C for 30 minutes decreased precipitate levels, suggesting antigen-antibody dissociation.
• Progressive concentrations of IgG increased precipitate formation, indicating heat-aggregated immunoglobulin activity.
• Repeated freezing and thawing (10 cycles) increased precipitate optical density, with a more pronounced effect in pathological sera compared to normal sera.

Conclusions:

• The polyethylene-glycol precipitation test is a viable method for detecting circulating immune complexes.
• Heat treatment and repeated freeze-thaw cycles influence the stability and detection of immune complexes, with the latter having a less significant impact.