Antiphospholipid antibodies in heart transplant recipients

Antiphospholipid antibodies (aPA) are found in patients with systemic lupus erythematosus, aPA syndrome, myocardial infarction, and stroke. The presence of aPA may predict recurrent events in certain victims of heart attack and stroke. Blood samples from 105 cardiac transplant recipients (81 men, 24 women) were tested by enzyme-linked immunosorbent assay (ELISA) for the presence of IgG, IgM, and IgA aPA to phosphatidylserine (PS), cardiolipin (CL), and phosphatidylethanolamine (PE). Patients' ages ranged from 17 to 70 years (mean 51 years). Collection times ranged from Day 1 to 9 years post transplant (mean 36 months). All patients received triple immunosuppressive therapy. We report our aPA ELISA results in multiples of the normal median (MoM) of the OD405 values calculated for 252 healthy individuals. A positive MoM is greater than the MoM that encompasses 95% of the controls; for example, above 3 MoM is considered positive for IgG anti-CL, IgA anti-PS, and CL. Above 4 MoM is positive for IgG anti-PS and PE and IgM anti-PS and CL. Thirty-nine patients had IgG anti-PS (range 4.1-14.8 MoM), 63 had IgG anti-CL (3.1-9.4 MoM), 7 had IgM anti-PS (4.1-12.1 MoM), 1 had IgM anti-CL (14 MoM), 47 had IgA anti-PS (3.1-13.1 MoM), and 58 had IgA anti-CL (3.1-11.5 MoM). In our patient population, the incidence of IgG and/or IgA aPA was significantly higher (p < 0.001) than IgM. Few patients showed specificity for either PS, CL, or PE, and many were positive with more than one antibody isotype. Because aPA were evaluated in these patients, we investigated pretransplant serum samples which are available from 79 of the 105 recipients, and found aPA in 52 of 79 (66%) patients before transplantation. Longitudinal studies were done in three patients: two had increasing IgA aPA, beginning on Days 13 and 26 post transplant, whereas the third patient showed an increased aPA on Day 8 but a decrease on Day 23. Studies are in progress to determine whether a correlation exists between the presence of aPA, immunocytochemical (biopsy) findings, and clinical outcome.