ABO-blood-group-related idiotypic network: mimicry of oligosaccharide epitope by rabbit antiidiotypic antibodies to murine monoclonal anti-A antibody

Assessment of severity and mortality of COVID-19 with anti-A1 and anti-B IgM isohaemagglutinins, a reflection of the innate immune status

AIMS

The relationship between the innate immune system that creates the polysaccharide antibody response and COVID-19 is not fully understood. In this study, it was aimed to determine the predictive values of isohaemagglutinins in COVID-19 severity/mortality.

METHODS

Approximately 15 440 patients diagnosed with COVID-19 were examined, and a total of 286 patients with anti-B and anti-A1 IgM isohaemagglutinins test results were randomly enrolled in the study. These patients were stratified into two groups according to anti-A1 (n: 138 blood type B or O) and anti-B (n: 148 blood type A) IgM isohaemagglutinins. Anti-A1 or/and anti-B IgM, biochemical parameters, symptoms, chronic diseases, hospitalisation status, intubation status, admission to intensive care unit (ICU) and exitus status were recorded and evaluated for all patients.

RESULTS

Anti-A1 IgM and anti-B IgM were significantly lower in ICU patients (7.5 ± 9.9 vs 18.0 ± 20.4 and 5.5 ± 6.3 vs 19.3 ± 33.6 titres, respectively; P < .01) and in exitus patients (3.8 ± 3.6 vs 16.7 ± 18.7 and 3.5 ± 4.7 vs 16.9 ± 29.6 titres respectively; P < .01). In the ROC analysis performed to differentiate between exitus and discharge within groups, the sensitivity of anti-B IgM and anti-A1 IgM at cut-off ≤4 was 88.9% and 79.6%, specificity 66.0% and 73.4%, and AUC 0.831 and 0.861, respectively (P < .01). Anti-A1 IgM decreased the mortality risk 0.811 times per unit while anti-B IgM decreased 0.717 times (P < .01).

CONCLUSION

Anti-B and anti-A1 isohaemagglutinins, which are an expression of the innate immune system, can be used to predict the severity and mortality of COVID-19 disease.

Is the ABO incompatibility a risk factor in bone marrow transplantation?

ABO histo-bloodgroups are strong transplantation antigens. In bone marrow transplantation, foreign ABO red cell antigens are not ignored by the immune system of the host, neither by the immunocompetent cells of the graft. Although ABO incompatibility is not considered a contraindication in bone marrow transplantation (BMT), its clinical consequences are still a matter of investigation. An overview of reports published by different groups is given and discussed. They present conflicting data regarding the role of the ABO match between patient and donor in the haematopoietic stem cell (HSC) transplantation. We report on the clinical outcome of bone marrow transplantation in 223 patients who received grafts from MHC identical siblings. Included are 139 ABO identical, 32 ABO minor mismatched, 34 major mismatched and 13 bi-directionally mismatched pairs. The statistical evaluation of standard parameters used to monitor the post-transplant period gave a proof that in neither group of patients with an ABO incompatible donor the recovery and success rate of transplantation, including the relapse incidence, risk of graft vs. host disease (GVHD) or overall survival, were significantly inferior. However, in all three cohorts of ABO mismatched patients, a delayed recovery of neutrophils was recorded as compared to the group receiving an ABO compatible graft. These finding leads us to the conclusion that the ABO compatibility is not a disadvantage in BMT, whereas the delayed recovery of neutrophils in patients having received an ABO mismatched graft is probably reflecting a transient humoral process leading to immune tolerance and graft accommodation.

[Target epitopes of monoclonal antibodies against ABH structures]

Comparing the reactivities of murine and human monoclonal antibodies directed against the antigens of A, B, and H blood groups by using different techniques (agglutination, inhibition by synthetic oligosaccharides and salivary antigens, tissue immunofluorescence, the use of an anti-idiotype antibody) enabled us to show a high heterogeneity of anti-A, anti-AB antibodies and, to some extend, anti-B and anti-H antibodies. Despite this diversity, the determination of the antibody specificity thanks to synthetic antigens made it possible to distinguish several groups of anti-A, B, AB, and H antibodies and to establish a classification that takes also their reactivity towards salivary and tissue antigens into account. On the contrary, few correlations were found between these tests and the ability of antibodies to agglutinate red blood cells of the different ABO-system variants.