Page 1919 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 110 Human Blood Group Antigens and Antibodies 1699

Yt Blood Group System have been benign. Anti-Ge3 has caused HDFN, and similar to Kell
The Yt system was named in 1956 when an antibody was found in antibodies, the disease is associated with severe anemia. Clinical
a
the serum of patient whose last name was Cartwright. Yt occurs with HDFN associated with anti-Ge2 has not been reported, but the
b
a prevalence of more than 99% in random blood samples, and Yt is antibodies have been eluted from DAT-positive cord RBCs.
found with a prevalence of approximately 8%, except in Israelis, in
whom it has a prevalence of 20% or higher. Cromer Blood Group System
The Cromer (Cr) antigens are carried on decay-accelerating factor
Antibodies Yt antibodies usually are IgG and do not bind comple- (DAF, CD55), a complement control protein attached to the RBC
ment. These antibodies have caused DHTR but not HDFN. membrane through GPI-linkage. Cr is a system of two sets of anti-
b
c
a
a
b
thetical antigens (Tc /Tc /Tc and WES / WES ), 16 high-prevalence
Scianna Blood Group System antigens, and three low-prevalence antigens. The Cr(a−) phenotype
The Scianna (Sc) antigens are expressed by the RBC adhesion protein, is the least rare of the negative phenotypes, and with the exception
erythrocyte membrane-associated protein. Sc1 is a high-prevalence of one Spanish-American woman, all people with Cr(a−) RBCs are
antigen (prevalence ≈99.9%), and Sc2 is a low-prevalence antigen black. Most of the other phenotypes are exceedingly rare.
(1%); there are five other Scianna antigens.
Antibodies Antibodies in the Cr system are usually IgG and do not
Antibodies Sc antibodies are usually IgG, and some bind comple- bind complement. The antibodies have caused mild DHTR but not
ment. These antibodies have not caused DHTR, and although they HDFN.
have caused a positive DAT in cord RBCs, they have not caused
HDFN. Several examples of autoanti-Sc1 have been reported, some Knops Blood Group System
reactive in tests using patient serum but not plasma. Autoanti-Sc3– The Kn blood group antigens are carried on complement receptor 1
a
a
a
like antibodies have been described in one patient with lymphoma (CR1). Kn , Sl , and McC antigens are fairly common and have a
a
and in one patient with Hodgkin disease whose RBCs had suppressed similar prevalence (>90%) in different populations; however, Sl is
Sc antigens. 2 present on RBCs of 98% of whites, but on only 60% of African
Americans. Typing for Kn system antigens can be challenging because
Dombrock Blood Group System the low level of expression on the RBCs in some disease processes
Dombrock (Do) antigens are carried on a GPI-linked glycoprotein gives false-negative results. RBC CR1 is important in the processing
that is a member of the mono-ADP-ribosyltransferase family, although of immune complexes, binding them for transport to the liver and
Do has no demonstrable enzyme activity on the RBC. The Do blood spleen for removal from the circulation. The CR1 copy number per
a
b
group system consists of two antithetical antigens, Do and Do , RBC (and thus antigen strength) is reduced in SLE, cold agglutinin
and eight other antigens of high prevalence. The null phenotype disease, paroxysmal nocturnal hemoglobinuria (PNH), hemolytic
is Gy(a−). anemia, insulin-dependent diabetes mellitus, acquired immunodefi-
ciency syndrome, some malignant tumors, and any condition associ-
a
b
Antibodies Do and Do antigens are poor immunogens, and anti- ated with increased clearance of immune complexes. CR1 (the Sl a
b
a
Do and anti-Do are rarely found as single specificities. Antibodies antigen in particular) may act as a receptor for the malarial parasite
in the Do system are usually IgG and do not bind complement. These Plasmodium falciparum; thus the Sl(a−) phenotype may provide selec-
antibodies have caused DHTR and a positive DAT but no clinical tive advantage.
HDFN.
Antibodies Antibodies in the Kn system are usually IgG, and they
Colton Blood Group System do not bind complement. The antibodies do not cause DHTR or
The Colton (Co) antigens are carried on aquaporin-1 (AQP-1), the HDFN, and once identified, they can usually be ignored for clinical
first water channel protein characterized in mammals, and are also purposes. Identification may be complicated by the fluctuation of
a
found in the kidney. The function of AQP-1 in RBCs may be to antigen expression on RBCs. In the Kn system, anti-Kn is the most
a
rehydrate rapidly after shrinking in the hypertonic environment of common antibody in whites, and anti-Sl is the most common in
a
the renal medulla. Co has a prevalence of 99.9%, its antithetical African Americans.
b
antigen Co has a prevalence of 10%, and Co3 and Co4 are present
on all RBCs except those of the very rare Co(a−b−) null phenotype. Indian Blood Group System
Co4 is a high prevalence antigen, the absence of which has been seen The antigens of the In system are carried on CD44. CD44 has a
in three families only. Apparently healthy propositi with the Co(a−b−) diverse range of biologic functions involving cell-cell and cell-matrix
phenotype and AQP-1 deficiency have RBCs with an 80% reduction interactions in cells other than RBCs. It is an adhesion molecule in
in the ability to transport water. The residual water transport in these lymphocytes, monocytes, and some tumor cells. CD44 binds to
RBCs may be through another member of the water channel protein hyaluronate and other components of the extracellular matrix and is
family, AQP-3, which transports water, glycerol, and urea, and carries also involved in immune stimulation, as well as signaling between
b
a
the blood group antigen GIL. cells. In is a common antigen, and In is rare in white persons but
has a prevalence of 4% in Indians, 10% in Iranians, and nearly 12%
Antibodies Antibodies in the Co system are usually IgG and in Arabs.
some bind complement. The antibodies have caused DHTR and
HDFN. Antibodies Antibodies in the Indian system are usually IgG and do
not bind complement. Some antibodies may directly agglutinate
Gerbich Blood Group System RBCs, but the reactivity is greatly enhanced by the IAT. These
The Gerbich system antigens are carried on glycophorin C (GPC) antibodies have caused decreased RBC survival and a positive DAT
b
and glycophorin D (GPD). There are six high-prevalence antigens in the neonate but not HDFN. A severe DHTR caused by anti-In
and five low-prevalence antigens. The two glycoproteins are products has been reported.
of the GYPC gene. The gene consists of four exons, and the smaller
GPD is generated by the use of an alternative translation initiation Chido/Rodgers Blood Group System
site. Although the Ch and Rg antigens are readily detected on RBCs, they
are located on the fourth component of complement (C4), which
Antibodies The antibodies may be immune or naturally occurring. becomes bound to RBCs from the plasma. In complement activation
Most are IgG and some of these bind complement. Some antibodies through the classic pathway, C4 becomes bound to the RBC mem-
may be IgM. Although some antibodies have caused DHTR, others brane and undergoes further cleavage; ultimately, a tryptic fragment,