Background: Detection of IgG antibodies using an indirect anti-globulin analysis is generally useful as a clinical laboratory examination. IgG has four subclasses, of which IgG1 and IgG3 have high complement binding activities which are reported to be frequently involved in hemolytic reactions. The purpose of this study was to evaluate the clinical significance of IgG subclasses regarding the respective alloantibodies or autoantibodies.

Methods: We measured fluorescence intensities by flow cytometry to investigate titers of erythrocyte-bound IgG subclasses in patients (n = 185) with anti-D, anti-E, anti-c, anti-e, anti-Fy^b, anti-Di^a, anti-Jk^a, anti-Jk^b and warm autoantibodies. Further, we performed monocyte monolayer assay (MMA) in about 30 of these cases to confirm clinical significance.

Results: The IgG subclasses IgG1 and IgG3 were common as a single antibody, while IgG1+IgG3 was common as multiple antibodies. In patients with anti-E antibody, single antibody with IgG1 or multiple antibodies with IgG1+IgG3, respectively, were common. High levels of cell-bound IgG3 showed a high phagocytic ratio in MMA.

Conclusions: IgG3 and IgG1+IgG3 alloantibodies in patients with anti-E antibody warrant further investigation.

In recent years, the shortage of immunoglobulin has become a serious issue worldwide. Japan is facing a similar situation, especially since 2019, due to the rapid increase in immunoglobulin usage, and the need for urgent imports is unavoidable. We analyzed two factors that immediately preceded the surge in immunoglobulin consumption: approved indications for the prevention of chronic inflammatory demyelinating polyneuropathy (CIDP) progression and launches of concentrated preparations. Although the use of the immunoglobulin for CIDP demonstrated a continuing upward trend, there was no significant increase before or after approval. However, the launch of a concentrated preparation, 10% Venoglobulin^® (Japan Blood Products Organization (JB) ), has led to shorter treatment times and changes in the form of treatment from inpatient to outpatient or home-based care, especially in patients with hypogammaglobulinemia and agammaglobulinemia (PID/SID) requiring continuous administration, which has resulted in a sharp increase in the use of the immunoglobulin. This may be because treatment needs hidden by hospitalization were unearthed with the increased availability of outpatient treatment. In the future, as companies strive to shorten treatment time, additional needs will be created for diseases that require continuous medication.

In the midst of the heated international plasma products market, careful debate is needed on how far to promote the appropriate use of immunoglobulin, how to extend approved indications, and how to adjust the quantity of demand.

To reduce the risk of transmission of human parvovirus B19 (B19), the causative virus of erythema infectiosum, through contaminated blood products, the Japanese Red Cross Blood Center introduced chemiluminescent enzyme immunoassay (CLEIA) screening for B19 antigen (CLEIA-B19) in 2008. CLEIA-B19 was then replaced in April 2019 with a novel chemiluminescent immunoassay (CLIA) for B19 antigen (CLIA-B19). Here, we evaluated the sensitivity of CLIA-B19 regarding B19 genotypes. Panels of all three genotypes, 1, 2 and 3, which were quantified for DNA concentration by real-time PCR, were tested. Donor samples that were positive by CLIA-B19 screening were tested for B19 DNA and their B19 isolates were phylogenetically analyzed. CLIA-B19 could detect all three genotypes of B19, with inferred sensitivity for the genotype samples of approximately 6.4log IU/ml. From April 2019 to March 2020, of 237 (0.09%) CLIA-B19-positive samples from 252,956 donations in Hokkaido, Japan, 26 (0.01%) were positive for B19 DNA and clustered exclusively with genotype 1. Our data indicate that CLIA-B19 is a useful method for the screening of blood donations having all genotypes of B19.

A 53-year-old man undergoing immunosuppressive therapy was treated by platelet transfusion for severe aplastic anemia. 47 minutes after the start of transfusion, abdominal pain and nausea, diarrhea, and vomiting were observed, followed by chills and fever of 38 °C. Gastrointestinal tract infection was suspected and abdominal CT was performed. Results showed gastrointestinal edema, and he was diagnosed with gastrointestinal tract infection. Blood transfusion was continued, and was completed after 2 h 50 min. Blood cultures were collected, and antibiotics were administered 3 h 50 min after transfusion. Endotoxin was markedly high at 188,900 pg/ml. From the blood culture, Citrobacter koseri (C. koseri) was detected. Culture of residual specimens in the transfusion bag also detected C. koseri, which was found to be of the same strain on later genetic analysis. On the fourth day, septic shock, anuria, hypoxemia occurred. He was transferred to the ICU and placed under artificial respiration management, with continuous filtration dialysis and endotoxin adsorption therapy performed in combination. His condition gradually improved.

In transfusion-derived bacterial infection, atypical early symptoms can make diagnosis difficult and may require more attention, particularly in immunosuppressed patients.