Crossmatching is essentially an in vitro "transplant in a tube" that is made up of recipient serum and donor lymphocytes to detect pre-formed antibodies or cell death. Crossmatching can be done between deceased donors, living donors, and autologous/self.
The purpose of crossmatching is to predict successful transplants of organs and to prevent organ rejections from acute or chronic graft-versus-host disease (GVHD) or host-versus-graft disease (HVGD). We consider the HLA genotype to find matches and confirm those matches with CDC and/or Flow Cytometry Crossmatching.
Complement Dependent Cytotoxicity Crossmatch (CDC XM) involves live donor cells incubated with patient serum in the presence of anti-human globulin (AHG) and complement to see if preformed HLA IgG or IgM antibodies are present, which can activate complement and cause cell lysis. The CDC XM is considered the least sensitive method and highly subjective compared to flow cytometry because the interpretation of live and dead cells as a percentage is subjective and prone to error (Table 2).
In CDC XM:
- Donor T and B lymphocytes are separated in 96 well micro-titer trays and patient serum is added.
- Complement is added and anti-human globulin (AHG) may be added to some of the trays to enhance antibody activities.
- A fluorescent dye is used to assess living and dead cells. Dead cells cannot efflux the stain and will fluoresce red, whereas live cells are green.
- The amount of live and dead cells are compared and reported as 0 to 8+ depending on the percentage of cell death.
CDC crossmatching is useful for heart and lung transplants.
Table 2. CDC XM and the Significance of those Results.| % of Cell Death | Score | Significance |
| 0-10% | 0 | Negative |
| 11-20% | 2+ | Borderline Negative |
| 21-50% | 4+ | Weak Positive |
| 51-80% | 6+ | Positive |
| 81-100% | 8+ | Strong Positive |
13. Kentzel, Ethan. "CDC XM visual." 16 Apr 2021.
