Introduction: Warm antibody-mediated autoimmune hemolysis (WAIHA) is most often due to immunoglobulin G (IgG) antibodies and is detected by direct antiglobulin test (DAT). However, about 10% cases of hemolytic anemia are DAT negative. Herein, we describe a patient with DAT-negative hemolytic anemia due to an anti-IgA antibody. We investigate if isolated IgA can promote erythrophagocytosis.
Methods: We isolated patient and control IgA on Jacalin agarose. Isolated IgA was used to sensitize healthy ABO/Rh-matched donor red blood cells (RBC). Antibody binding was examined by flowcytometry. The effect of IgA on erythrophagocytosis was evaluated using Macrophage colony stimulating factor 1 (M-CSF)-differentiated autologous macrophages by Giemsa staining and immunofluorescence microscopy.
Results: We show that isolated IgA from the serum can bind to red cells. In addition, RBCs were phagocytosed efficiently by autologous macrophages in the presence of patient IgA.
Conclusion: Our results show that IgA antibodies are capable of inducing erythrophagocytosis like IgG antibodies in the absence of complement fixation.
Keywords: IgA antibodies; autoimmune; hemolysis; phagocytosis; trogocytosis.
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