Characterization of the Anti-HLA Class I and II IgG Antibodies in Moroccan IVIg Using Regular Beads and Ibeads in Luminex Multiplex Single Antigen Immunoassay

Therapeutic Immunoglobulin Intravenous (IVIg), approved to treat a wide range of autoimmune and primary immunodeficiency diseases, contain mixture of polyreactive and polyclonal IgG purified from the pooled plasma of thousands of donors. The aim of this study is to characterize the profiles of anti- Human Leukocyte Antigen (HLA) class-I and class-II IgG antibodies in four lots of Moroccan IVIg preparations using Luminex Multiplex Single Antigen Bead Immunoassay and to compare it with the unique high frequency HLA types found in the Moroccan population. Anti-HLA class I IgG profiles were assessed using regular (Labscreen) Beads and iBeads. The regular beads are coated with all conformational and structural variants of HLA-I (HLA heavy chain (HC) with β2-microglobulin (β2m) with or without peptides, β2m-free HC with or without peptides or HC only), quite contrast to iBeads, which contained only native tissue-associated HLA HC with β2m and with or without peptides. The level of antibodies was measured as Mean Fluorescent Intensity (MFI). The reactivity of anti-HLA-I IgG antibodies to different alleles of HLA-I loci differed in their recognition of native HLA-I and other structural variants of the HLA-I. High MFI IgG antibodies in the IVIg corresponded with several high frequency HLA-I alleles (B*0801, B*5001, Cw*0602 and Cw*0702) and HLA-II haplotypes (DQA1*0201-DQB1*0201/DRB1*0301), which accounted for 50% of the total gene frequencies in the Moroccan population. HLA-I reactivity of the IVIg with iBeads confirms that the IgG reacting to normal tissue associated with peptide -associated or -free β2mHC. These findings caution the use of high dose IVIg for the carriers of the high frequency HLA types for it may cause tissue injury. The β2m-free-HC reactivity of IVIg indicates the potential of IVIg to bind to activated T and B cells that express these variants, to suppress antibody production. Such an immunomodulation by IVIg renders benefit for patients with autoimmune diseases and organ transplantation.