The Monocyte Monolayer Assay (MMA): An Adjunct to Compatibility Testing

Transcription

1 The Monocyte Monolayer Assay (MMA): An Adjunct to Compatibility Testing Ghislain Noumsi MD,SBB(ASCP) CM Molecular ImmunoHematologist Scientific Support Services LifeShare Blood Centers Shreveport, LA

2 Objectives Review the mechanism of RBC destruction by alloantibody Describe the MMA technique Analyze the MMA impact as secondary crossmatch method for patients with RBC alloantibody(ies)

3 Blood bank response to blood request Request and specimen received Initial investigation Interpretation and additional test Crossmatch Blood delivered Patient transfused No reaction (hemolysis)

4 Sometimes things are more complicated!!! Any decision can have a direct impact on the patient prognosis

5 Meet the transfusion request Requested Phenotypes Total number of requests (n=141) Requests completely filled Requests partially filled Requests unfilled Number % Number % Number % All patients Patients with SCD Total % of requests for rare RBCs unfilled or partially filled (1 out of 7 patients) over a 18 months period. Flickinger C. Immunohematology 2006,22(3): Central Europe (Germany, Austria, Switzerland): transfusion support for one-third (1/3) of patient with RBC antibody to high incidence antigen was unsatisfactory. Seltsam et al. Transfusion 2003,43:

6 Meet the transfusion request Requested Phenotypes Total number of requests (n=141) Requests completely filled Flickinger C. Immunohematology. 2006;22(3): Requests partially filled Requests unfilled Number % Number % Number % U-,D Js(b-) U-,D r r Hy Jo(a-) E-,hr B Lu(b-) K I Ge: E-,hr S Total

7 What is the clinical significance of my antibody(ies)? A clinically significant RBC antibody is defined as an antibody that is frequently associated with HDFN, with hemolytic transfusion reactions, or with a notable decrease in the survival of transfused RBCs. AABB Technical Manual. 16 th Ed. P466 In vivo: RBCs are considered incompatible if their survival is curtailed by the presence of clinically significant alloantibody

8 Factors related to the antibody Binding constant Ig class and IgG subclass Ability to bind to macrophage Fc receptors Ability to activate complement Thermal reactivity range Plasma concentration

9 Factors related to the antigen Antigenic determinant epitope Distribution in the body Abudance of sites on the red cell Appearance on the fetus RBC and placenta (in case of evaluation of risk of HDFN) Association with complement activation Other: antigen expression and modification during storage; number of RBC transfused etc

10 Factors affecting the antigen-antibody bond formation Spatial complementarity between antigen and antibody: Lock and Key concept Weak non-specific intermolecular forces including: electrostatic charges (ionic groups), hydrogen bonds, hydrophobic (non-polar) bonds, Van der Waals forces The equilibrium (association) constant of the Ag-Ab formation

11 Factors related to the mononuclear phagocytic system (RES) The Fc receptor polymorphism: The phagocytic activity of the mononuclear phagocytic system (RES)

12 Where do we go from here? Do we just STOP? One element missing in the above pathogenesis process can result in normal survival of antigen positive RBCs!!!

13 The Monocyte Monolayer Assay (MMA) In vitro assay Predict the outcome of transfused antigen positive RBCs to patients with corresponding antibody Predict the risk of HDFN in maternal alloimmunization with feto-maternal incompatibility

14 Early development Stevens JO, Braley JF, Schanfield MS. Detection of clinically significant IgG antibodies by an in vitro human peritoneal macrophage phagocytosis assay. Transfusion 1976; 16:523 Arndt PA, Garratty G. A retrospective analysis of the value of monocyte monolayer assay results for predicting the clinical significance of blood group alloantibodies. Transfusion 2004;44:

15 MMA

16 MMA: Monocyte Index (MI%) ROBERT TEMPKIN MI = number of monocytes with one or more RBCs adhered and/or ingested divided by the total number of monocytes x 100

17 Interpretation Arndt PA, Garratty G. Transfusion 2004;44: MI values of 5% have indicated that incompatible blood can be given without the risk of an overt hemolytic transfusion reaction but it does not guarantee normal long-term survival of those RBCs

18 Can MMA be used as a secondary crossmatch technique for patients with unusual antibodies presentation?

19 RBC units tested and MI distribution RBC antibodies Number of RBC units tested Monocyte index (MI) > 20 hr B Fy AnWj Yt a Js b LW Rg Lu b Jr a Hy Co a Tc a Lan U hr S Multiple antibodies Unidentified high Total

20 Number of RBC units transfused Antibodies Specificities (Anti-) Number of RBC units tested Number of RBC with MI < 5% Number of RBC units transfused Number % hr B Fy AnWj Yt a Js b LW Rg Lu b Jr a Hy Co a Tc a Lan U hr S Multiple antibodies Unidentified high Total

21 25 MI > 20 Serological crossmatch reactivity vs MMA Tube-Saline 4 (60-37C/AHG)

22 Antibody Specificity and MI distribution Antibody Specificity (Anti-) Number of source Monocyte index distribution (MI) > 20 hr B Fy AnWj Yt a Js b LW Rg Lu b Jr a Hy Co a Tc a Lan U hr S

23 PREDICTING THE CLINICAL SIGNIFICANCE OF 51 RBCs ALLOANTIBODIES USING MONOCYTE MONOLAYER ASSAY (MMA): A 5 YEAR REVIEW NOUMSI GT, BILLINGSLEY K, MOULDS JM, MOULDS JJ

24 Conclusion Positive crossmatch: In vivo, the capacity of an antibody to curtail RBCs survival involves other pathways and. THIS IS A COMPLETELY DIFFERENT STORY!!!

25 When all RBCs seems to be crossmatch incompatible think MMA you may be SURPRISED!!!

26 Thank you!!!