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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Antibody Screen Positive: Rh Disease and Other Atypical Antibodies
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7. Rh Disease and Other Atypical Antibodies
Step 7. Other Atypical Antibodies
Again, though not Rh antibodies, you may get reports on these antibodies, as well
Others: More worrisome
Kidd Blood Group
The biochemistry of the Kidd blood group system has yet to be elucidated; the carrier molecule is known to be a multipass membrane protein. Anti-Jka, and to a lesser extent anti-Jkb, are responsible for a great percentage of serious hemolytic transfusion reactions. The reasons are threefold:
Kidd antibodies, which are usually IgG, will bind complement and can cause in vivo hemolysis.
The antibodies will often react much better with cells containing a double dose of the antigen (eg, Jk(a+b-) than a single dose (Jk(a+b+), and in fact a Jk(a+b+) donor unit might be compatible in vitro, but incompatible in vivo.
Kidd antibodies tend to disappear rapidly from the circulation and may not be detectable using very sensitive serologic techniques the next time the patient requires transfusion.
Others: Less worrisome
MNSs Blood Groups
Basic biochemistry — The M and N antigens are carried on glycophorin A and the S and s antigens are carried on glycophorin B, both of which are sialoglycoproteins. MN antigens are closely linked with the Ss antigens and generally will be inherited together.
Anti-M is usually an IgM or cold reactive IgG antibody. It can be naturally occurring and will sometimes react better if the patient's serum is acidified. The antibody rarely is the cause of transfusion reactions unless it is reactive at body temperature. HDN has only rarely been reported, primarily in U-M- individuals.
Anti-N is generally considered to have little if any clinical significance. It is almost always IgM in nature, and may be found as an autoantibody in dialysis patients whose equipment was sterilized with formaldehyde. Anti-En(a) is capable of causing severe hemolytic transfusion reactions (HTRs) and HDN. Fortunately, the En(a-) phenotype is extremely rare.
Both anti-S and anti-s are capable of causing hemolytic transfusion reactions, although the majority are mild to moderate in nature. Anti-S and anti-s are mainly IgG, and thus can cross the placental barrier and cause HDN. Severe cases are rare. Anti-S will frequently be found as an underlying alloantibody in patients with warm autoantibodies. Anti-U can cause both severe HTRs and severe HDN. Since 1 percent of blacks lack the U antigen, anti-U can present as a relatively common serologic problem. If no anti-U is available to screen for compatible donors and a relatively large black donor population exists, soybean lectin may be used for screening, since it will react with red cells containing reduced amounts of sialic acid (eg, U(-) RBCs).
