d. Identification of Cold Autoantibody.
(1) The specificity of cold autoantibodies can be demonstrated by testing
against a reagent RBC panel, or the special panels described below. Cord cells (i)
should be used, and (i) adult cells, if available. For the autocontrol, cells free of the
absorbed antibody should be used. (See step three in cold-absorption procedure.)
(2) If agglutination patterns are unclear, a clue to, specificity can often be
achieved by testing diluted serum against cells positive and negative for the suspected
antigen, usually I or one of the I compIexes. In Table 1-8 the specificity is anti-I and the
patient's RBCs react as strongly as other I-positive cells.
NOTE:
When such titration studies are done, it should be borne in mind that any
alloantibody contained in the serum will also be diluted. If the alloantibodies
are of low titer, they may then be undetected. For this reason, autoabsorbed
serum is preferred.
Test Red Blood Cells
Dilution
l-pos
l-pos
l-pos
i (adult)
i (cord)
i (cord)
Auto
Neat
++++
++++
++++
+
+
+
++++
1:16
++
++
++
W+
W+
W+
++
1:32
+
+
+
0
0
0
+
1:64
W+
0
W+
0
0
0
W+
1:28
0
0
0
0
0
0
0
Table 1-8. ldentification of anti-I.
e. Special Panels.
(1) Anti-I agglutinates all adult cells, except those from rare i-adults, but
gives much weaker or negative results with cord cells containing small amounts of I
antigen and much larger amounts of i antigen. Anti-i agglutinates cord cells and the
rare adult i cells much more strongly than the majority of adult cells.
(2) Anti-lH agglutinates cells according to the amount of H present on the
cells: group O cells have the most, then A2, B, A1, A1B. Group O cord cells react
somewhat less strongly with the anti-H than group adult cells.
(3) Anti-lH agglutinates only those cells possessing both H and I antigens;
thus, it does not agglutinate group O cord cells.
(4)
Anti-A1 agglutinates A1 or A1B cells, but does not affect A2 or O cells.
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