Types of HLA Crossmatches: Flow Cytometry Crossmatching (FXM)

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The page below is a sample from the LabCE course The Human Leukocyte Antigen (HLA) System. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Types of HLA Crossmatches: Flow Cytometry Crossmatching (FXM)

An auto-crossmatch can also be performed when troubleshooting unexpected reactivity from other methods. This procedure uses patient serum with patient cells.

Auto-crossmatching can be done using flow cytometry, complement dependent cytotoxicity (CDC), or ELISA/solid phase methods.
Flow cytometry is the most sensitive method for crossmatching. It detects recipient IgG antibodies that have reacted with donor antigens on the surface of T and B lymphocytes. This uses anti-human globulin labeled with fluorescent dyes.
The graphic to the right shows a typical FXM. The X axis represents the degree of fluorescence from labeled anti-human globulin bound to recipient/patient HLA antibodies that are already bound to donor lymphocyte HLA antigens. The Y cell is the number of cells. Movement up the Y and right on the X axis are increasing values. Patient serum and donor lymphocyte values are compared to positive and negative control serum to determine positive or negative FXM.
14. Kentzel, Ethan. "Flow Cytometry Crossmatching (FXM) visual." 16 Apr 2021.

Flow Cytometry Crossmatching (14).