Erythrophagocytosis in autoimmune immunoglobulin A-mediated hemolysis.

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.