In addition to the defined human blood group systems, there are

erythrocyte Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

antigens In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

which do not meet the definition of a blood group system. Most of these are either nearly universal in human blood or extremely rare and are rarely significant in a clinical setting. Reagents to test for these antigens are difficult to find and many cannot be purchased commercially.

Blood group collections

These three groups are antigens with shared characteristics but do not meet the

International Society of Blood Transfusion The International Society of Blood Transfusion (ISBT) is a scientific society founded in 1935, which promotes the study of blood transfusion and spreads reliable information about the ways in which blood transfusion medicine and science can bes ...

(ISBT) definition of a human blood group system. Further research may identify them as blood group systems. This antibody is associated with WBC. It is associated more with tissue antibodies than red blood cells. It has not been associated with autoimmune hemolytic anemia of the fetus. However, it does cause difficulty in the blood bank because it makes it more difficult to cross match blood for transfusions.

Cost

The Knops blood group system was formerly part of this collection. All that remains are the Cs^a and Cs^b antigens. Cs^a is a very high frequency (>98%) antigen and Cs^b is not uncommon (~34%).

Er

The Er collection includes one high incidence (>99%) antigen, Er^a and one (<1%) rare antigen, Er^b.

Vel

The Vel collection includes the high incidence Vel and ABTI antigens. Antibodies to Vel have been implicated in transfusion reactions.

Other high-incidence antigens

These antigens are almost universally present on human red cells, but their absence has been noted in some individuals and some have been associated with transfusion reactions or other problems. Finding compatible units for transfusion to a patient that lacks one of these antigens is a major challenge and some countries maintain rare

donor A donor in general is a person, organization or government which donates something voluntarily. The term is usually used to represent a form of pure altruism, but is sometimes used when the payment for a service is recognized by all parties as rep ...

registries specifically for that purpose. *AnWj Antigen: the receptor for ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...

''. Implicated in severe

hemolytic transfusion reactions An acute hemolytic transfusion reaction (AHTR), also called immediate hemolytic transfusion reaction, is a life-threatening reaction to receiving a blood transfusion. AHTRs occur within 24 hours of the transfusion and can be triggered by a few milli ...

Other low incidence antigens

These antigens are extremely rare and are of little concern in selecting compatible units for transfusion. They may be implicated in rare cases of

hemolytic disease of the newborn Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis foetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five ...

, however. *Batty (By) *Biles (Bi) *Box (Bx^a) *Christiansen (Chr^a) *HJK *HOFM *JFV *JONES *Jensen (Je^a) *Katagiri (Kg) *Livesay (Li^a) *Milne *Oldeide (Ol^a) *Peters (Pt^a) *Rasmussen (RASM) *Reid (Re^a) *REIT *SARA *Torkildsen (To^a) *Bg (Bennett-Goodspeed): These are actually

Human Leukocyte Antigens The human leukocyte antigen (HLA) system or complex is a complex of genes on chromosome 6 in humans which encode cell-surface proteins responsible for the regulation of the immune system. The HLA system is also known as the human version of th ...

that cause confusing results on serological tests of erythrocytes.

References

* Mark E. Brecher, Editor (2005), ''AABB Technical Manual'', 15th edition, Bethesda, MD: AABB, , p. 355 {{transfusion medicine Blood antigen systems