The action of papain and bromelain, prepared over a pH range from 4.6 to 8.6, was evaluated for the
ability to render red cells agglutinable by five incomplete antibodies of differing blood group specificities using a
two-stage technique. The optimal pH for treatment of red cells by activated papain or bromelain was between 5.4 and
5.8. Above this pH range, a fall in serological sensitivity was apparent which was much more pronounced with papain
than with bromelain. The optimal pH for enzyme treatment of red cells can be achieved in two-stage techniques, but
not in one-stage techniques due to the buffering effect of serum proteins.
A two-stage papain technique is described in which cell washing after papain treatment is replaced by the
addition of a specific papain inhibitor. This technique permits optimal enzyme treatment of red cells while digestion
of immunoglobulin following the addition of serum is avoided. The technique therefore combines the design and
consequent sensitivity advantage of two-stage tests with the convenience of one-stage tests, rendering it suitable for
use in compatibility testing.
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