An auto-antibody anti-Vel

CRISPR/Cas9-Editing K562 Cell Line as a Potential Tool in Transfusion Applications: Knockout of Vel Antigen Gene

Introduction

The Vel- phenotype is a rare blood group, and it is challenging for identifying this phenotype due to limited available reagents. Moreover, there are relatively few studies on genomic editing of erythroid antigens and generation of knockout (KO) cell lines at present.

Methods

To identify the high-efficiency small-guiding RNA (sgRNA) sequence, candidate sgRNAs were transfected into HEK 293T cells and analyzed using Sanger sequencing. Following this, the high-efficiency sgRNA was transfected into K562 cells using lentivirus transduction to generate KO Vel blood group gene cells. The expression of the Vel protein was detected using Western blot on single-cell clones. Additionally, flow cytometry was used to detect the erythroid markers CD235a and CD71. Hemoglobin quantification and Giemsa staining were also performed to evaluate the erythroid differentiation of KO clones induced by hemin.

Results

The high-efficiency sgRNA was successfully obtained and used for CRISPR-Cas9 editing in K562 cells. After limiting dilution and screening, two KO clones had either deleted 2 or 4 bases and showed no expression of the Vel protein. In the hemin-induced KO clone, there was a significant difference in erythroid marker and hemoglobin quantification compared to untreated cells. The morphological changes were also observed for the hemin-induced KO clone.

Conclusion

In this study, a highly efficient sgRNA was screened out and used to generate Vel erythroid antigen KO single-cell clones in K562 cells. The edited cells could then be induced to undergo erythroid differentiation with the use of hemin.

SMIM1 at a glance; discovery, genetic basis, recent progress and perspectives

Recent elucidation of the genetic basis of the Vel blood group system has offered the field of blood transfusion medicine an additional consideration in determining the causes of hemolytic reactions after a patient is transfused. The identification of the SMIM1 gene to be responsible for the Vel blood group allows molecular based tools to be developed to further dissect the function of this antigen. Genetic signatures such as the homozygous 17 bp deletion and the heterozygous 17 bp deletion in combination with other single nucleotide polymorphisms (SNPs) and insertion sequences regulate the expression level of the gene. With this knowledge, it is now possible to study this antigen in-depth.

An infant girl with severe autoimmune hemolytic anemia: apparent anti-Vel specificity

Autoantibodies directed against the common red-cell antigen Vel are unusual, with only 2 previous cases reported. This report describes an infant girl with steroid-resistant autoimmune hemolytic anemia whose serum contained an antibody with apparent specificity for Vel antigen. Transfusion with Vel-positive cells resulted in a massive hemolytic transfusion reaction. Survival of labelled Vel-negative cells was normal up to 8 h following transfusion, and no transfusion reaction followed subsequent use of Vel-negative cells. There was no evidence of a collagen vascular disease, an immunodeficiency syndrome, or a malignancy. Although rare, anti-Vel should be considered in unexplained autoimmune hemolytic anemia.

Autoimmune hemolytic anemia and the Kell blood groups

Approximately one in 250 people with autoimmunity involving their red cells have IgG autoantibodies with specificity in the Kell blood groups. Red cells of these individuals have an acquired temporary weakening of their Kell antigens. Some of the patients also have allo-anti-K in their serum. This report presents a case in which an IgG autoantibody may define a new high-incidence red cell antigen related to the Kell blood groups. The patient's Kell blood group antigens are depressed, and his serum contains allo-anti-K. It is postulated that reduced red cell Kell antigenicity is caused by enzymatic degradation, possibly of bacterial origin, and that the acquired loss of Kell antigens, the Kell-specific autoimmune state, and the serum all0-anti-K, are all related aspects of one phenomenon.

The Vel blood group in northern Sweden

Using the potent anti-Vel, Paul., a detailed study of the Vel blood group has been made in the Northern region of Sweden. Family studies have shown Vel to be independent of P1, though some association with P groups was detected since P2 was more frequent amongst Vel(-) than expected. The frequency of Vel(-) was 0.0006.