Re: Blood Irradiation for GVHD -Reply

[Martin Gerard Carolan <carolanm@doh.health.nsw.gov.au>]

For those interested in Blood -

The general idea of irradiating blood to prevent GVHD is to inactivate the lymphocytes present in the donor blood. GVHD is caused by donor T-lymphocytes proliferating in the recipient if for some reason they are not recognised as foriegn.  Among those at risk for GVHD are neonates, immune compromised patients (on chemo etc) or patients closely related to the donor. 

The literature seems to suggest that platlet damage is not clinically significant at 30Gy so long as the platelets are used within a few days of irradiation. 

Red blood cells also do not show clinically significant damage at 30 Gy. Some investigators have seen elevated plasma potassium in the blood of the  recipient if the blood has been stored for more than a few days post irradiation. I guess this is a result of damaged or "leaky" cell membranes.

Apparently physically filtering out the majority of white cells is inadequate to prevent GVHD so a few more logs of lymphocyte kill are required. This can be achieved with irradiation. There is the odd report in the literature of GVHD after irradiation at 15 Gy. The suggested dose has increased over the last few years and 30 Gy now seems to be the norm.

But I am not a hematologistor a radiobiologist ! - check out some of these references for more info:

Lowenthal et al in  Transfusion 1993, 33(6), 524-529
Rosen et al in Transfusion 1993 33(2), 125-127
Dzik eta la in Transfusion 1993 33(6), 493-496
Masterton et al in Med Phys, 1992, 19(3), 649-657
          
Apologies if this is getting too far off topic.

Martin Carolan
Physicist
Wollongong Hospital
Australia

carolanm@doh.health.nsw.gov.au
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