Terminology Home Page

Human blood groups were discovered in 1900 and since then a variety of different styles of terminology has been used to denote them. In 1980 the International Society of Blood Transfusion (ISBT) established a Working Party (later to become a Committee) to devise a genetically based numerical terminology for red cell surface antigens. The mandate of the Committee is to maintain the numerical terminology for red cell surface antigens. By definition, these antigens must be defined serologically by the use of a specific antibody. All antigens receiving ISBT numbers must have been shown to be inherited characters. The information presented on this website is an update of the latest publication of the Committee.

All authenticated antigens fall into one of four classifications: systems, collections, low incidence antigens (700 series), and high incidence antigens (901 series).

A blood group system consists of one or more antigens controlled at a single gene locus, or by two or more very closely linked homologous genes with little or no observable recombination between them.

Collections consist of serologically, biochemically, or genetically related antigens, which do not fit the criteria required for system status.

The 700 Series contains antigens with an incidence of less than 1% and which cannot be included in a system or collection.

The 901 Series contains antigens with an incidence of greater than 90% and which cannot be included in a system or collection.

Antigens, phenotypes, genes and genotypes

Each antigen belonging to a blood group system is identified by a 6-digit number. The first 3 digits represent the system (e.g. 006 for Kell), the second 3 the specificity (e.g. 006003 for Kp^a). Alternatively, the system symbol followed by the antigen number may be used (e.g. KEL003 or, more usually, KEL3 as sinistral zeros may be removed).

Phenotypes are represented by the system symbol, followed by a colon, followed by a list of antigens separated by commas. Those antigens shown to be absent are preceded by a minus sign (e.g. KEL:–1,2,–3,4).

Genes are designated by the system symbol, followed by an asterisk, followed by the antigen number, all italicised (e.g. KEL*3).

Genotypes have the system symbol, followed by an asterisk, followed by alleles or haplotypes separated by a slash, all italicised (e.g. KEL*2,3/2,4).

Antigen, phenotype, gene, and genotype designations for collections are constructed in the same way.

For the 700 and 901 series, 700 or 901 replaces the system symbol.

A 'popular', alternative terminology

The numerical terminology was devised primarily for computer storage of information on blood group antigens and to provide a framework for a genetical classification. The numerical terminology is not suitable for everyday communication and many scientists working in the field of human blood groups prefer not to use it in publications. This has led to a variety of alternative names being used for some blood group antigens. In an attempt to introduce some uniformity, a recommended list of alternative names for antigens is provided (see table). In most cases the name or symbol is identical to that originally published, but in a few cases the more commonly used name is provided. In addition, there are recommended formats for describing phenotypes in the alternative terminology (see table).

Criteria for the establishment of new blood group systems

For an antigen to form a new blood group system it must be defined by a human alloantibody, be an inherited character, the gene encoding it must have been identified and sequenced, and its chromosomal location known. In addition the gene must be different from, and not a closely-linked homologue of, all other genes encoding antigens of existing blood group systems.

Criteria for the inclusion of a new specificity in an established system

All antigens awarded an ISBT number must have been shown to be inherited and at least one of the following four criteria must be met.

(1) An antithetical relationship between a new antigen and one already assigned to the system.

(2) Demonstration that expression of the antigen is associated with a variation in the nucleotide sequence of the gene controlling the system.

(3) Evidence, from a linkage analysis of family data, that the controlling allele is probably a newly recognised form of the pertinent gene, and supporting serological or biochemical information.

(4) Demonstration that an antigen is located on a protein or glycoprotein that carries other antigens belonging to the system. It must be remembered, however, that this could result from post-translational modification of a gene product, such as glycosylation, which would not support inclusion within the system.

Criteria for establishment of a blood group collection

A collection must contain two or more antigens that are related serologically, biochemically, or genetically, but which do not fit the criteria required for system status.

Criteria for inclusion in the 700 series

(1) Incidence of <1% in most populations tested.

(2) Distinction from all other numbered low incidence antigens of the 700 series as well as those of the blood group systems and collections.

(3) Demonstration of inheritance through at least 2 generations.

Criteria for inclusion in the 901 series

(1) Incidence of >90% in most populations tested.

(2) Distinction from all other numbered high incidence specificities.

(3) Demonstration that the antigen is lacking from the red cells of at least 2 sibs, i.e. that the negative phenotype is genetically determined.

Obsolete Numbers

Once a number has been allocated to a specificity, that number cannot be subsequently used for any other specificity. Consequently, if the number of a specificity becomes inappropriate, then that number becomes obsolete. Obsolete numbers are listed in a table.

Procurement of ISBT Numerical Designations

Symbols for designations of new specificities will consist of 3-6 on-line capital letters and must not duplicate, alphabetically or phonetically, any current or obsolete symbols shown in the tables. Also, symbols used in related fields, such as those used for platelet and leucocyte antigens, must be avoided. Symbols for specificities that may herald new blood group systems, and thus new genes, have the further constraint that they must differ from any symbols given to genes by the HUGO Nomenclature Committee (http://www.genenames.org/)

Procedures for acquisition of an ISBT number

The initial stipulation is that materials for defining the new specificity be available for either circulation or in-house testing. Proposals should be submitted with supporting data to the members of the Committee listed below, who are authorised to allocate numbers provisionally in consultation with the Chair. All decisions must be ratified by the Committee before being finalised.

For a new blood group system or collection: Dr Geoff Daniels.

For a specificity number within an established system: Dr Marion Reid for the MNS system; Dr Silvano Wendel or Ms Christine Lomas-Francis for the Rh system; Dr Jan Jørgensen for other systems.

For a specificity number in a current collection: Dr Geoff Daniels.

For a 700 number: Dr Teresa Zelinski.

For a 901 number: Dr Geoff Daniels.

Links to relevant web sites

International Society of Blood Transfusion http://www.isbt-web.org/

Blood Group Antigen Mutation Database http://www.bioc.aecom.yu.edu/bgmut/index.php

HUGO Gene Nomenclature Committee http://www.gene.ucl.ac.uk/nomenclature/

Return to Top