(4) "Immune" antibodies. Agglutinating anti-A and anti-B develop so
regularly after environmental exposure that they are considered naturally occurring;
for example, no recognizable immunizing event leads to their appearance. A person exposed
to a specific immunizing event may produce antibodies of the same specificity but different
biologic behavior. Immunizing events include pregnancy with an ABO-incompatible
fetus; transfusion of incompatible red blood cells or of plasma containing blood group
substances; injection of purified blood group substances; or inoculation with viral or
bacterial products containing blood-group-active materials. After immunization, the
subject's antibody may increase in titer or avidity; develop powerful hemolyzing
properties; become more difficult to neutralize with soluble blood-group substances; or
become more active at 37C. These changes are more common in group O subjects,
but may occur in group A or B persons as well. Although the distinction is not always
complete, naturally occurring antibodies tend to be IgM and "immune" activity is more
often IgG. Serologic characteristics of IgG and IgM Anti-A and Anti-B are as follows:
(a) Properties in Common
Agglutinate red blood cells in saline suspension
React well at room temperature
Present in serum of group O persons
May cause hemolysis in "in-vitro" testing
(b) Distinguishing Features
IgM
Antibody titer can be enhanced by use of enzymes,
cold temperature
Readily neutralized by soluble blood-group substances
Inactivated by two-mercaptoethanol or dithiothreitol
Predominant isoagglutinin in group A and B persons
IgG
Antibody titer can be enhanced by warm temperature
and use of antiglobulin technique
Only partially neutralized by soluble blood group substances
Unaffected by two-mercaptoethanol or dithiothreitol
Seldom conspicuous in unimmunized A or B persons
2-11. GENERAL PRINCIPLES FOR ALL SEROLOGIC TESTING
a. Document the strength, specificity, and behavioral characteristics of all
reagents by a regular quality assurance program.
MD0845
2-14