Autoimmune Hemolysis: A Journey through Time

Prior immunization against an intracellular antigen enhances subsequent red blood cell alloimmunization in mice

Antibodies against red blood cell (RBC) alloantigens can increase morbidity and mortality among transfusion recipients. However, alloimmunization rates can vary dramatically, as some patients never generate alloantibodies after transfusion, whereas others not only become alloimmunized but may also be prone to generating additional alloantibodies after subsequent transfusion. Previous studies suggested that CD4 T-cell responses that drive alloantibody formation recognize the same alloantigen engaged by B cells. However, because RBCs express numerous antigens, both internally and externally, it is possible that CD4 T-cell responses directed against intracellular antigens may facilitate subsequent alloimmunization against a surface RBC antigen. Here, we show that B cells can acquire intracellular antigens from RBCs. Using a mouse model of donor RBCs expressing 2 distinct alloantigens, we demonstrate that immune priming to an intracellular antigen, which would not be detected by any currently used RBC compatibility assays, can directly influence alloantibody formation after exposure to a subsequent distinct surface RBC alloantigen. These findings suggest a previously underappreciated mechanism whereby transfusion recipient responders may exhibit an increased rate of alloimmunization because of prior immune priming toward intracellular antigens.

Immunohematological and clinical characterizations of mixed autoimmune hemolytic anemia

BACKGROUND AND AIM:

Patients with warm autoimmune hemolytic anemia (AIHA) may carry immunoglobulin (Ig) M antibodies that react at room temperature and are nonpathological, but few may have cold agglutinins that react at or above 30°C and are referred to as “mixed” AIHA (MAIHA). Here, we present our experience on characterizing MAIHA both clinically and serologically.

MATERIALS AND METHODS:

Out of 134 AIHA patients, 13 diagnosed as MAIHA were subjected to detailed immunohematological characterization. Most patients were severely anemic and required urgent transfusions. Resolution of blood group discrepancy, elution, Donath-Landsteiner test, and adsorption study were performed following established protocol. “Best match” blood units were selected and transfused to patients.

RESULTS:

Eight of the 13 patients had severe hemolysis. The median age of patient was 37 years with a female preponderance and secondary MAIHA was observed in 8 (61.5%) patients. Blood group discrepancy was encountered in 4 (30.8%) patients. Multiple red cell bound autoantibodies and high titer serum-free IgM autoantibodies were detected in all samples. Twenty-nine units of “best match” packed red blood cells were transfused to 12 patients without any adverse reaction. Improvement in hematological and biochemical values was observed in all follow-up patients.

CONCLUSION:

Patients with MAIHA often present with severe hemolysis necessitating blood transfusions. While red cells are coated with multiple autoantibodies, both warm reactive IgG and cold reactive IgM autoantibodies are present in the serum. These serological complexities not only render a crossmatch incompatibility but often lead to blood group discrepancy. “Best match” blood transfusion is always lifesaving.

Efficacy and safety of splenectomy in adult autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) is a rare hematologic disease, primarily affecting adults or children with immunodeficiency disease. First-line therapy consists of long course of steroids administration, with an early complete response rate (CRr) of 75-80%, but up to 20-30% of patients requires a second-line therapy. Rituximab is the first choice in refractory old AIHA patients, because of its safety and efficacy (early CRr at 80-90% and at 68% at 2-3 years). For this reason, splenectomy is even less chosen as second-line therapy in elderly, even though laparoscopic technique decreased complication and mortality rates. However, splenectomy can be still considered a good therapeutic option with a CRr of 81% at 35.6 months in patients older than 60 year-old, when rituximab administration cannot be performed.

Loss-of-function mutations in the C9ORF72 mouse ortholog cause fatal autoimmune disease

C9ORF72 mutations are found in a significant fraction of patients suffering from amyotrophic lateral sclerosis and frontotemporal dementia, yet the function of the C9ORF72 gene product remains poorly understood. We show that mice harboring loss-of-function mutations in the ortholog of C9ORF72 develop splenomegaly, neutrophilia, thrombocytopenia, increased expression of inflammatory cytokines, and severe autoimmunity, ultimately leading to a high mortality rate. Transplantation of mutant mouse bone marrow into wild-type recipients was sufficient to recapitulate the phenotypes observed in the mutant animals, including autoimmunity and premature mortality. Reciprocally, transplantation of wild-type mouse bone marrow into mutant mice improved their phenotype. We conclude that C9ORF72 serves an important function within the hematopoietic system to restrict inflammation and the development of autoimmunity.