Section II. THE ANTIGLOBULIN TEST
1-15. PRINCIPLES OF THE ANTIGLOBULIN TEST
a. In 1945, Coombs, Mourant, and Race described a test that detected
nonagglutinating (coating) Rh antibodies in serum, and later used the same test to
demonstrate "in vivo" coating of RBCs with antibodies. In 1957, Dacie et al. showed
that complement components attached to the RBC could also be detected by the test.
This test, now known as the antiglobulin test, depends on the following simple
"In vivo" means something is measured, seen, or tested inside a living
organism. "In vitro" means something is measured, seen, or tested outside a
living organism after it has been removed from that organism.
Antibody molecules and complements components are globulins.
(2) If an animal (for example, rabbit or goat) is injected with human globulin
(either purified or in whole human serum), the animal will make antibodies to the foreign
protein (for example, antihuman globulin, AHG).
(3) This antiglobulin serum, after suitable treatment, will react specifically
with human globulin. If this globulin (for example, antibody or complement) is attached
to the RBC membrane, the antiglobulin serum will combine with globulin on adjacent
RBCs, and cause agglutination of the sensitized RBCs. Nonsensitized RBCs will not
react (see figure 1-5).
b. As mentioned in Section I, most blood group antibodies are lgM or lgG. Most
lgM antibodies can be detected by direct agglutination; thus, the principal purpose of the
antiglobulln test is to detect lgG nonagglutinating (sensitizing) antibodies. In certain
circumstances, it may be advantageous to detect RBC-bound lgA, lgM and/or
complement components by this test.
c. The antiglobulin test can be used to detect "in vivo" or "in vitro" RBC