Evaluation of the functional properties of cryopreserved buffy coat-derived monocytes for monocyte monolayer assay

Monocyte monolayer assay in pre-transfusion testing: A magic key in transfusing patients with recurrent bad cross-match due to alloimmunization

BACKGROUND

The monocyte monolayer assay (MMA) is an in-vitro assay that can predict the outcome of blood transfusion of antigen positive units when serologically compatible blood is not available.

MATERIALS AND METHODS

Fifty-four patients testing positive by the antibody screening test using gel agglutination were further examined by the alloantibody identification panel to determine alloantibody specificity. After determining and categorizing the antibodies, patients' samples were examined using the MMA to determine the clinical significance of the detected alloantibodies. We also tested 2 seeding methods (24-well cell culture plates versus 8-well chamber-slides) and 3 visualization/staining techniques (unstained phase contrast, Leishman and Giemsa staining).

RESULTS

35 out of the 54 cases (64.8%) had a monocyte index of >5% which is predictive of occurrence of hemolytic reaction after transfusion; 23 cases with antibodies known to be clinically significant [anti-C, anti-E, anti-c, anti-K, anti-Fy(a), anti Fy(b), anti-JK(b)], 2 with Anti-M specificity, 7 cases with autoantibodies and 3 cases with multiple antibodies. On the other hand, 19 out of the 54 (35.2%) cases included in the study showed a monocyte index of <5% which is predictive of absence of hemolytic reaction after transfusion. The 8-well chamber-slides were better than the 24-well culture plates, as the latter showed a lot of un-phagocytosed RBCs in the background. Also, Leishman staining was better than Giemsa staining with better and clearer differentiation between the RBCs, monocytes and phagocytic vacuoles.

CONCLUSION

MMA can be used as a surrogate cross-match test for the selection of blood units in cases where antigen-negative blood units are not available.

Platelet vesicles are potent inflammatory mediators in red blood cell products and washing reduces the inflammatory phenotype

BACKGROUND

Studies suggest that washing red cell concentrates (RCCs) to remove soluble mediators and/or inflammatory components, such as extracellular vesicles (EVs), may lead to better clinical outcomes. This study tested the hypothesis that non-red blood cell (RBC) generated vesicles in RCC are potent inflammatory mediators in vitro and washing RCCs can reduce these vesicles and subsequently decrease the inflammatory activity of RCCs.

STUDY DESIGN AND METHODS

Sixteen RCCs were pooled and split into four groups based on pre-wash storage time (Day 2 or 14; n = 4/group). Each group was tested 24 hours and 7 days post-wash. Characteristics of RBCs and EVs, cytokines released by monocytes, and expression of human umbilical vein endothelial cells (HUVECs) adhesion molecules were assessed.

RESULTS

All RCCs meet quality standards for hemolysis, hematocrit, and hemoglobin. Washing did not remove residual platelets from RCCs but led to a significant reduction in platelet-EV count regardless of the group. Supernatant of RCCs washed on Day 14 and stored for 24 hours had significantly lower concentrations of RBC-EVs and white blood cell EVs compared to unwashed controls. Supernatant of unwashed RCCs showed higher production of inflammatory cytokines/chemokines MCP-1, IL-8, and TNF-α, and heightened expression of HUVEC VCAM-1, which were significantly reduced by washing. Spiking washed RCC supernatants with platelet-EVs showed significant increase in IL-8, MCP-1, VCAM-1, and E-selection in groups washed on Day 14.

CONCLUSIONS

Platelet-EVs in RCCs are associated with pro-inflammatory activity. As washing significantly reduced RCC immunomodulatory activity, implementation of this process may improve transfusion outcomes.