Circulating immune complexes involving the ABO system after platelet transfusion

Area of Science:

• Immunology
• Hematology
• Transfusion Medicine

Background:

• ABO unmatched platelet transfusions may lead to circulating immune complexes (CIC).
• CIC formation involves soluble ABH antigens and transfused antibodies, potentially causing platelet destruction.
• Platelet destruction can occur via bystander mechanisms or CIC binding to platelet receptors.

Purpose of the Study:

• To investigate the presence of CIC in patients receiving platelet transfusions.
• To determine if CIC formation is associated with platelet refractoriness.
• To confirm the hypothesis that ABO unmatched transfusions induce CIC.

Main Methods:

• An ELISA C1q assay was used to detect CIC in 40 patients with hematological diseases.
• Serum fractionation via gel exclusion chromatography identified IgG anti-A in monomeric and high molecular weight forms.
• Purified IgG anti-A fractions were tested for group A antigen using dot immunoblotting.

Main Results:

• 41% of refractory patients were positive for CIC compared to 13% of non-refractory patients and 0% of controls.
• High molecular weight IgG anti-A (200-900 kD) was detected in six group A refractory patients.
• Group A antigen was associated with purified high molecular weight IgG anti-A in 4/5 patients.

Conclusions:

• Refractory patients receiving ABO unmatched platelets exhibit CIC composed of ABO antigens and antibodies.
• These CIC circulate for several days and are linked to transfusion refractoriness.
• The study confirms that ABO unmatched transfusions can induce CIC in hematological patients.