Blood Group System
Definition
A set of red cell surface antigens encoded by one gene locus or by two tightly linked loci. The International Society of Blood Transfusion recognises more than 40 systems; the MNS, Kell, Kidd, and Duffy systems were the most used in forensic serology.
- Definition
- Set of red cell antigens from one gene locus or tightly linked loci
- Recognised systems
- 40+ per the International Society of Blood Transfusion
- Historically used in forensics
- MNS, Kell, Kidd, Duffy, alongside ABO
- Current forensic status
- Largely superseded by DNA STR profiling
Common questions
Why did forensic serologists use multiple blood group systems together rather than just ABO?+
ABO alone divides a population into only a handful of groups, which gives weak individualising power. Combining several independent systems, each contributing its own set of possible phenotypes, multiplied the discriminating power in a way similar to how multiple STR loci are combined in DNA profiling today.
Why are systems like MNS and Kell rarely used in casework now?+
Antigen typing from dried bloodstains requires intact protein, which degrades faster and is harder to work with than DNA, and it offers far less discriminating power per test than STR profiling. Once reliable forensic DNA methods became available, blood group phenotyping was retained mainly for historical case review or specific transfusion-medicine contexts.
Related terms
- Absorption-Elution
- A technique for detecting antigens on dried red cell debris. Specific antiserum is absorbed onto the stain; if the antigen is present,...
- Antiserum
- Serum collected from an immunised animal containing antibodies directed against a specific antigen or group of antigens. In species identification, antiserum raised...
- Linkage Disequilibrium
- The non-random association of alleles at different loci within a population. Certain HLA allele combinations (e.g., HLA-A1 with HLA-B8 with HLA-DR3) occur...
- Phenotype Frequency
- The proportion of a given population that expresses a particular antigen combination. Multiplying phenotype frequencies across independent loci gives the combined frequency...
- Probability of Exclusion
- The proportion of the population whose blood type differs from that of the stain and who would therefore be excluded as its...