Anti-phospholipid antibody isotypes in normal human sera

Area of Science:

• Immunology
• Autoimmunity
• Serology

Background:

• Antiphospholipid antibodies (aPL) are associated with autoimmune diseases like Systemic Lupus Erythematosus (SLE).
• The presence and significance of aPL in normal human sera (NHS) remain incompletely understood.
• Heat-labile factors in serum may interfere with aPL detection.

Purpose of the Study:

• To investigate the role of heat-sensitive cofactors in masking aPL in NHS.
• To determine the prevalence and isotypes of unmasked aPL in normal individuals.
• To compare aPL reactivity in NHS with that in SLE patients after heat treatment.

Main Methods:

• Heat inactivation of NHS at 56°C.
• Enzyme-Linked Immunosorbent Assay (ELISA) for aPL detection.
• Isotype analysis (IgG, IgM, IgA) of detected aPL.

Main Results:

• Heat inactivation at 56°C specifically inactivated serum masking cofactors for aPL.
• Unmasked aPL in NHS showed binding levels comparable to aPL-reactive SLE sera.
• Previously "negative" SLE sera also demonstrated increased reactivity after heat inactivation.
• Significant prevalence of IgG (34/36), IgM (11/36), and IgA (24/36) aPL was found in NHS.
• 31% of NHS possessed all three aPL isotypes, and 36% had both IgG and IgA aPL.

Conclusions:

• Normal human sera contain functionally significant, heat-labile aPL.
• Heat treatment is crucial for accurate aPL assessment, potentially unmasking antibodies in both healthy and autoimmune individuals.
• The study reveals a higher prevalence of aPL in the general population than previously recognized.