Transfusion significance of LWa allo-antibodies.

An example of anti-LWa, arising as a complication during a RhD immunization programme, has been studied for evidence of its likely in vivo haemolytic properties. In vitro testing of the anti-LWa showed it to be largely IgG1 acting by the antiglobulin technique. Results of antibody-dependent cellular cytotoxicity and macrophage phagocytic assays were both negative. However, 99mTc-labelled Lw(a+) donor cells showed a slight reduction in t1/2 (18 h) compared with the normal survival of autologous cells. Despite this observation, and bearing in mind the difficulties of interpreting apparently accelerated destruction of small serologically incompatible red cells, it was concluded that the presence of this example of anti-LWa should not be a bar to urgent transfusion.