(2) When the cells from two or more donors are pooled, no less than 50
percent of the cells should have each of the antigenic determinants needed. Weak
antibodies may not be detected when RBCs are pooled. Pooling reagent RBCs is not
recommended for screening the serum of patients, but may be used when screening the
serum of donors. It is likely that low-incidence antigens such as Lua, Cw, Kpa, and Wra
will not be found on detection cells. Therefore, antibodies with these specificities will be
detected only when a panel must be run because of another antibody present in the
serum, if a cross match is incompatible with supposedly compatible cells, or if a
newborn is born with jaundice or develops jaundice soon after delivery.
c. For Antibody Identification.
(1) Panels of RBCs are composed of selected group O RBCs from several
people tested for as many as possible of the common antigenic determinants. A panel
should include some RBCs that possess--and some that lack -- these determinants, in
such a manner that a distinct pattern of reaction is available for single antibodies to all
or most of the antigens represented on the panel.
(2) Commercial panels will vary and contain from 8 to 10 different samples.
Some include special cells either lacking a high-incidence antigen or having a
Low-incidence antigen. Some provide a sample of cord cells.
(3) Another source of interesting RBCs for testing is the donor or patient
found to lack either combinations of common antigens, or a high-incidence antigen, or
to have a low-incidence antigen.
a. Complement is important to the reaction of some antibodies. Serum of
normal people stored at 4C for up to two weeks will have sufficient complement activity.
It is hard to generalize about patients whose proteins may be diminished. Seventy-two
hours is usually the maximum time suggested for optimal activity. Serum rather than
plasma must be used because Ca++ and Mg++ ions are necessary to the
b. Because immunologic cell lysis is an important indication presence of some
antibodies, the serum should be free of hemolysis. Because this is not always possible,
tests that show any degree of hemolysis should be compared with the color of the
c. Cell-free serum can be kept in the refrigerator or frozen for longer storage.
Serum stored in the refrigerator on the clot will show increased hemolysis as the
storage period extends. Specimens, that are to be retained for more than a few days,
should have the serum removed, and the two tubes should be stopped, or covered with