(4) Serum. lgM cold agglutinins are usually present to a titer of greater than
1,000 at 4C. They are usually between 2,000 and 64,000, but have been reported
higher than 1,000,000. The agglutinin does not usually react above 32C when normal,
untreated RBCs are used, but in the presence of 30 percent albumin, most of them will
react up to 37C. Hemolytic activity against untreated RBCs can often be demonstrated
at room temperature (20C--25C) and enzyme-treated RBCs are always hemolyzed in
the presence of adequate complement. The lgm antibodies associated with cold
chronic aggultinin syndrome are monocional proteins, almost always of the kappa light
chain type. The antibodies associated with M. pneumoniae show normal kappa and
lambda light chain distribution. Rare examples of lgA and lgG cold agglutinins have
been described.
(5) Specificity. The most common specificity associated with cold agglutinin
syndrome is anti-l; less commonly, anti-i is found, (these are usually associated with
infectious mononucleosis); on rare occasions, anti-Pr, (also called anti-Sp1), is seen. It
is very difficult to determine the specificity of these cold agglutinins, unless titrations are
performed. As one raises the temperature, the specificity becomes more apparent. For
instance, at 4C an anti-l may react to a titer of 1:2,000 with adult l cells and 1:256 with i
(cord) cells, but, at 25C, it may still react to a titer of 1:128 with adult cells and give no
reaction with cord cells. If adult i cells are available, specificity is more obvious. Anti-i
obviously gives the opposite results, reacting with adult i cells more strongly than i
(cord) cells, and much weaker with adult cells. If all cells are equally agglutinated, a
mixture of anti-l + i or anti-Pr should be suspected. Anti-Pr is easily distinguished as the
antigen is destroyed by enzyme treatment, whereas both anti-l and anti-i give much
higher titers against enzyme-treated cells; therefore, if both adult and cord cells give
much weaker reactions after enzyme treatment, anti-Pr should be strongly suspected.
To confirm the results if mixtures of antibodies are suspected, absorption and elution
studies should always be carried out. These are not as simple, as when working with
other blood-group systems, as no cells completely lacking the respective antigens are
available.
Compatibility testing.
(6)
(a) Patients suffering from cold agglutinin syndrome should not need to
be transfused often, as, once diagnosed, they are told to avoid the cold; hemolysis is
minimal. If the need arises, compatibility procedures should be performed with the
principles that have been discussed previously kept in mind.
(b) It is advisable, if time allows, to absorb out the cold autoagglutinin
using the patient's own cells. The main purpose, of this, is to ensure that no
alloantibodies are present that may be masked by the cold agglutinin. Complete
absorption of these high-titer cold agglutinins is very time-consuming. It helps to
enzyme-treat the patient's RBCs prior to autoabsorption, but it is still a long, tedious
procedure. Often, there is insufficient time to absorb sufficiently and blood may have to
be issued regardless. It is a useful modification to set up room temperature
MD0846
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