Mixed passive hemagglutination with soluble platelet antigens

Area of Science:

• Immunology
• Transfusion Medicine

Background:

• Platelet transfusions can lead to alloimmunization, necessitating accurate methods for detecting antibodies against human leukocyte antigens (HLA).
• Existing methods for antibody detection may have limitations in sensitivity or specificity for certain patient populations.

Purpose of the Study:

• To establish and evaluate a novel mixed passive hemagglutination (MPHA) test utilizing platelet supernatant for the detection of HLA antibodies.
• To assess the utility of this MPHA test in identifying HLA A or B antibodies in patients with multiple platelet transfusions.

Main Methods:

• Developed an MPHA test using indicator cells coated with anti-human IgG antibodies and platelet supernatant containing various antigens (HLA A, B, platelet alloantigens, blood group antigens).
• Compared the MPHA test with platelet supernatant to MPHA using platelet monolayers, and evaluated its performance on sera from patients with multiple platelet transfusions.

Main Results:

• The platelet supernatant contained HLA A and B antigens, along with other platelet-derived antigens.
• The MPHA test with platelet supernatant successfully detected HLA A or B antibodies in 44% (32 of 72) of patients with multiple platelet transfusions, including those with 'cytotoxicity negative absorption positive' sera.
• In vitro-formed immune complexes did not yield positive reactions, likely due to lower Fc receptor activity in platelet supernatants.

Conclusions:

• The developed MPHA test using platelet supernatant is a sensitive method for detecting HLA A or B antibodies.
• This assay is valuable for cross-matching sera in recipients of platelet transfusions and for screening HLA typing sera.